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Cited by 2,186Essential Oils and Antimicrobial ActivityAntimicrobial agents and applicationsInsect Pest Control Strategies

Effect of essential oils on pathogenic bacteria

Open access
Nazzaro, Filomena, Fratianni, Florinda, De Martino, Laura, Coppola, Raffaele, De Feo, Vincenzo·2013·Pharmaceuticals
DOI 10.3390/ph6121451PMC PMC3873673
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Abstract

The increasing resistance of microorganisms to conventional chemicals and drugs is a serious and evident worldwide problem that has prompted research into the identification of new biocides with broad activity. Plants and their derivatives, such as essential oils, are often used in folk medicine. In nature, essential oils play an important role in the protection of plants. Essential oils contain a wide variety of secondary metabolites that are capable of inhibiting or slowing the growth of bacteria, yeasts and moulds. Essential oils and their components have activity against a variety of targets, particularly the membrane and cytoplasm, and in some cases, they completely change the morphology of the cells. This brief review describes the activity of essential oils against pathogenic bacteria.

AI snapshot

Written from the paper’s full text.

TL;DR

This narrative review summarizes how essential oils and their components act against pathogenic bacteria, emphasizing membrane/cytoplasm disruption, fatty-acid and protein effects, ATP/ATPase inhibition, metabolome changes, morphology alterations, and anti-quorum-sensing activity. It concludes that activity is composition-dependent, often stronger against Gram-positive bacteria, and not attributable to a single mechanism.

Key findings

  • Gram-negative bacteria are generally more resistant to essential oils than Gram-positive bacteria; the Gram-positive cell wall is approximately 90%–95% peptidoglycan, whereas the Gram-negative peptidoglycan layer is 2–3 nm thick, composes approximately 20% of cell dry weight, and is covered by an outer membrane containing lipopolysaccharides.
  • Many terpenes have low or no inherent antimicrobial activity: limonene, α-pinene, β-pinene, γ-terpinene, δ-3-carene, (+)-sabinene, and α-terpinene showed very low or no antimicrobial activity against 25 genera of bacteria, and p-cymene did not show antimicrobial activity against many Gram-negative pathogens.
  • Thymol and carvacrol have similar antimicrobial activity against *B. cereus*, *S. aureus*, and *P. aeruginosa*; carvacrol disintegrates the outer membrane of Gram-negative bacteria and causes lipopolysaccharide release. Cinnamaldehyde at 60 μM reduced *V. harveyi* BB886 bioluminescence by 55%, and at 100 μM reduced *V. harveyi* BB170 bioluminescence by 60%.
  • Eugenol or carvacrol at 5 to 10 mM had bactericidal effects on *E. coli* and *L. monocytogenes*, while cinnamaldehyde had bactericidal activity against *E. coli* and *L. monocytogenes* at 10 mM and 30 mM concentrations, respectively. Mechanisms include increased membrane permeability, K+ and ATP leakage, reduced proton motive force, ATPase inhibition, altered fatty-acid profiles, protein and FtsZ effects, metabolome shifts, cell morphology changes, and anti-quorum-sensing activity.

Methods

  • Narrative review (“brief review”) of essential oils against pathogenic bacteria; no systematic review protocol, search strategy, inclusion/exclusion criteria, or primary experimental data are reported.
  • Evidence base consists of cited in vitro and model studies on bacterial species/strains and essential oil components; synthesis is qualitative and organized by chemical class and mechanism.
  • Main analysis is descriptive integration of reported mechanisms and examples; no meta-analysis or quantitative pooling is described.

Limitations

  • Stated in the paper: susceptibility is difficult to predict not only for a species but also for a strain within the same species; identifying the mode of action requires study of the raw material, singular components, and multiple strains and species; antimicrobial activity is not attributable to a unique mechanism but to a cascade of reactions.
  • Stated/evident: conflicting reports exist, for example on the role of carvacrol’s hydroxyl group and on cinnamaldehyde’s membrane-perturbing activity; the review is brief and narrative, without systematic search or quality appraisal.
  • Evident from the text: most evidence is in vitro, with no standardized comparison across essential oils, doses, strains, or methods, and no clinical or application data are synthesized.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.3390/ph6121451

Cites

135 of 135 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 225 cited sources checked · 0 supported · 0 flagged

  • Findingcitation

    Tea tree oil can cause E. coli to die without lysing the cell.

    “For example, tea tree oil can cause E. coli to die without lysing the cell [65].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [65] Gustafson, 1998, Effects of tea tree oil on Escherichia coli, Lett. Appl. Microbiol. source

      Not checked in the free run.

  • Findingcitation

    Essential oils are less able to affect the cell growth of Gram-negative bacteria than Gram-positive bacteria.

    “thus, EOs are less able to affect the cell growth of the Gram-negative bacteria [4].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [4] Burt, 2003, Antibacterial activity of selected plant essential oils against Escherichia coli O157:H7, Lett. Appl. Microbiol. source

      Not checked in the free run.

  • Findingcitation

    Cinnamaldehyde can decrease the in vitro assembly reaction and bundling of FtsZ.

    “cinnamaldehyde can decrease the in vitro assembly reaction and bundling of FtsZ.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [79] Domadia, 2007, Inhibition of bacterial cell division protein FtsZ by cinnamaldehyde, Biochem. Pharmacol. source

      Not checked in the free run.

  • Findingcitation

    S. enterica serovar Thompson MCV1 grown in the presence of a sub-lethal concentration of thymol showed a different proteomic profile compared with the control.

    “S. enterica serovar Thompson MCV1 grown in the presence of a sub-lethal concentration of thymol showed a different proteomic profile compared with the control [80].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [80] Mamone, 2010, Changes in the proteome of Salmonella enterica serovar Thompson as stress adaptation to sublethal concentrations of thymol, Proteomics source

      Not checked in the free run.

  • Findingcitation

    Glutamine transport enzymes are overexpressed by S. typhimurium in the presence of thymol in an attempt to increase the virulence of the bacteria.

    “Some enzymes, such as those involved in glutamine transport, are overexpressed by S. typhimurium in the presence of thymol in an attempt to increase the virulence of the bacteria [84].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [84] Klose, 1997, Simultaneous prevention of glutamine synthesis and high-affinity transport attenuates Salmonella typhimurium virulence, Infect. Immun. source

      Not checked in the free run.

  • The quote only partly states this claim. 2
  • May combine two claims. 84
  • Classified as probably not a substantial claim. 15

  • The quote only partly states this claim.

    Findingcitation

    Treatment of E. coli 0157:H7 and Salmonella enterica with mustard essential oil resulted in the loss of intracellular ATP.

    “The treatment of E. coli 0157:H7 strain EDL 933 and Salmonella enterica subsp enterica serovar typhi strain ATCC 19430 with mustard EO resulted in the loss of intracellular ATP in S. aureus [94].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [94] Caillet, 2009, Effect of gamma radiation and oregano essential oil on murein and ATP concentration of Staphylococcus aureus, J. Food Sci. source

      Not checked in the free run.

  • May combine two claims.

    Findingcitation

    Treatment of E. coli and L. monocytogenes with eugenol, cinnamaldehyde and carvacrol inhibited the generation of adenosine triphosphate from dextrose and disrupted the cell membrane.

    “The treatment of some pathogens, such as E. coli and L. monocytogenes, with eugenol, cinnamaldehyde and carvacrol inhibited the generation of adenosine triphosphate from dextrose and disrupted the cell membrane.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [45] Gill, 2004, Mechanisms of bactericidal action of cinnamaldehyde against Listeria monocytogenes and of eugenol against L. monocytogenes and Lactobacillus sakei, Appl. Environ. Microbiol. source

      Not checked in the free run.

  • May combine two claims.

    Findingcitation

    Cinnamaldehyde can perturb the Z-ring morphology in vivo and reduce the frequency of the Z-ring per unit of cell length of E. coli.

    “It also can perturb the Z-ring morphology in vivo and reduce the frequency of the Z-ring per unit of cell length of E. coli.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [79] Domadia, 2007, Inhibition of bacterial cell division protein FtsZ by cinnamaldehyde, Biochem. Pharmacol. source

      Not checked in the free run.

  • May combine two claims.

    Findingcitation

    Due to their hydrophobic nature, essential oils and/or their components can affect the percentage of unsaturated fatty acids (UFAs) and alter their structure.

    “Due to their hydrophobic nature, EOs and/or their components can affect the percentage of unsaturated fatty acids (UFAs) and alter their structure [4].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [4] Burt, 2003, Antibacterial activity of selected plant essential oils against Escherichia coli O157:H7, Lett. Appl. Microbiol. source

      Not checked in the free run.

  • May combine two claims.

    Findingcitation

    The DNA-binding protein H-NS and the 50S ribosomal proteins L7/L12 are down-regulated by thymol.

    “Other proteins, such as the DNA-binding protein H-NS and the 50S ribosomal proteins L7/L12, are down-regulated by thymol.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [82] Mauriello, 2013, Expression of DnaK, HtpG, GroEL and Tf chaperones and the corresponding encoding genes during growth of Salmonella Thompson in presence of thymol alone or in combination with salt and cold stress, Food Res. Int. source

      Not checked in the free run.

  • May combine two claims.

    Findingcitation

    Although similar concentrations of eugenol or carvacrol (5 to 10 mM) may have a bactericidal effect on E. coli and L. monocytogenes, there are large differences in response between the three organisms to cinnamaldehyde, which has bactericidal activity against E. coli and L. monocytogenes at 10 mM and 30 mM concentrations.

    “However, although similar concentrations of eugenol or carvacrol (5 to 10 mM) may have a bactericidal effect on E. coli and L. monocytogenes, there are large differences in response between the three organisms to cinnamaldehyde, which has bactericidal activity against E. coli and L. monocytogenes, at 10 mM and 30 mM concentrations [45].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [45] Gill, 2004, Mechanisms of bactericidal action of cinnamaldehyde against Listeria monocytogenes and of eugenol against L. monocytogenes and Lactobacillus sakei, Appl. Environ. Microbiol. source

      Not checked in the free run.

  • May combine two claims.

    Findingcitation

    Thymol up-regulates the outer membrane channel protein TolC, which is involved in an efflux system important for resistance to detergents and bile salts in Salmonella and may also be involved in resistance to thymol.

    “Thymol up-regulates the OM channel protein TolC that is involved in the formation of an efflux system that represents [83] an important mechanism of resistance to detergents and bile salts in Salmonella and may also be involved in resistance to thymol.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [83] Baucheron, 2005, TolC but not AcrB is essential for multidrugresistant Salmonella enterica serotype Typhimurium colonization of chicks, J. Antimicrob. Chem. source

      Not checked in the free run.

  • May combine two claims.

    Findingcitation

    Thymol affects the expression of proteins involved in energy metabolism: enolase is more than 10-fold up-regulated, while dPGM and glyceraldehyde-3-phosphate dehydrogenase A are down-regulated.

    “Thymol can also affect the expression of proteins involved in energy metabolism, such as enolase, which is more than 10-fold up-regulated in thymol-treated cells, the 2,3-bisphosphoglycerate-dependent phosphoglycerate mutase dPGM and the glyceraldehyde-3-phosphate dehydrogenase A, which are down-regulated [82].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [82] Mauriello, 2013, Expression of DnaK, HtpG, GroEL and Tf chaperones and the corresponding encoding genes during growth of Salmonella Thompson in presence of thymol alone or in combination with salt and cold stress, Food Res. Int. source

      Not checked in the free run.

  • May combine two claims.

    Findingcitation

    Treatment with thymol causes the up-regulation of some proteins and can trigger bacterial envelope stress due to the accumulation of mis-folded outer membrane proteins.

    “Treatment with thymol causes the up-regulation of some proteins and can trigger bacterial envelope stress due to the accumulation of mis-folded OM proteins.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [82] Mauriello, 2013, Expression of DnaK, HtpG, GroEL and Tf chaperones and the corresponding encoding genes during growth of Salmonella Thompson in presence of thymol alone or in combination with salt and cold stress, Food Res. Int. source

      Not checked in the free run.

  • May combine two claims.

    Findingcitation

    Cinnamaldehyde can inhibit the rate of GTP hydrolysis and binds to FtsZ with favourable enthalpic interactions.

    “Cinnamaldehyde can also inhibit the rate of GTP hydrolysis and binds to FtsZ with favourable enthalpic interactions.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [79] Domadia, 2007, Inhibition of bacterial cell division protein FtsZ by cinnamaldehyde, Biochem. Pharmacol. source

      Not checked in the free run.

  • May combine two claims.

    Findingcitation

    YidC depletion leads to a decrease in the functional assembly of cytochrome o oxidase and F1Fo ATPase and a strong reduction in the proton motive force in E. coli.

    “YidC depletion leads to a decrease in the functional assembly of cytochrome o oxidase and F1Fo ATPase and a strong reduction in the proton motive force in E. coli [90].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [90] Urbanus, 2003, A conserved function of YidC in the biogenesis of respiratory chain complexes, Proc. Nat. Acad. Sci. USA source

      Not checked in the free run.

  • May combine two claims.

    Findingnone given

    Treatment with thymol, carvacrol and eugenol may increase the amount of saturated C16 (and shorter length) fatty acids, increase the amount of saturated C18 and decrease the amount of unsaturated C18 fatty acids in the bacterial membrane.

    “Treatment with thymol, carvacrol and eugenol, which are all phenolic compounds, may increase the amount of saturated C16 (and shorter length) fatty acids, increase the amount of saturated C18 and decrease the amount of unsaturated C18 fatty acids in the bacterial membrane.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingnone given

    Cells defective in the production of UFAs can continue to grow and synthesise phospholipids, but they eventually begin to lose metabolites and subsequently lyse.

    “In some cases, cells defective in the production of UFAs can continue to grow and synthesise phospholipids, but they eventually begin to lose metabolites and subsequently lyse.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingcitation

    The concentration of aromatic amino acids remained stable at the lowest level of carvacrol but increased at higher doses.

    “The concentration of aromatic amino acids remained stable at the lowest level of carvacrol but increased at higher doses.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [107] Picone, 2013, Evaluation of the effect of carvacrol on the Escherichia coli 555 metabolome by using 1H-NMR spectroscopy, Food Chem. source

      Not checked in the free run.

  • May combine two claims.

    Findingnone given

    The S. typhimurium cell membrane was altered by carvacrol and thymol, and some of the cells showed swelling after treatment with thymol.

    “Indeed, the S. typhimurium cell membrane was altered by carvacrol and thymol, and some of the cells showed swelling after treatment with thymol.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingcitation

    Septa were present between the filamentous cells, but their formation was incomplete.

    “The septa were present between the filamentous cells, but its formation was incomplete.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [98] Kwon, 2003, Bactericidal effects and inhibition of cell separation of cinnamic aldehyde on Bacillus cereus, Lett. Appl. Microbiol. source

      Not checked in the free run.

  • May combine two claims.

    Findingcitation

    Formate increased until a certain dose of carvacrol and then drastically decreased to nearly zero; the increase in formate may indicate a possible metabolic shift toward fermentation.

    “Formate increased until a certain dose of carvacrol and then drastically decreased to nearly zero; the increase in formate (one of the main sugar molecules produced by E. coli during fermentation) may indicate a possible metabolic shift toward fermentation.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [107] Picone, 2013, Evaluation of the effect of carvacrol on the Escherichia coli 555 metabolome by using 1H-NMR spectroscopy, Food Chem. source

      Not checked in the free run.

  • May combine two claims.

    Findingcitation

    Cells treated with cinnamaldehyde for 1 h showed a strong inhibition of cell separation and appeared as filamentous cells.

    “Cells treated with cinnamaldehyde for 1 h showed a strong inhibition of cell separation and appeared as filamentous cells.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [98] Kwon, 2003, Bactericidal effects and inhibition of cell separation of cinnamic aldehyde on Bacillus cereus, Lett. Appl. Microbiol. source

      Not checked in the free run.

  • May combine two claims.

    Findingcitation

    Glucose tends to accumulate when microbial cells are treated with carvacrol, and the inability of the cells to metabolise the glucose leads to a loss of viability.

    “They found that glucose tends to accumulate when microbial cells are treated with carvacrol, and the inability of the cells to metabolise the glucose leads to a loss of viability.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [107] Picone, 2013, Evaluation of the effect of carvacrol on the Escherichia coli 555 metabolome by using 1H-NMR spectroscopy, Food Chem. source

      Not checked in the free run.

  • May combine two claims.

    Findingnone given

    S. typhimurium and Pseudomonas spp. cells treated with cinnamaldehyde and limonene presented external modifications, suggesting that these compounds penetrated the cell envelope and altered its structure.

    “S. typhimurium and Pseudomonas spp. cells treated with cinnamaldehyde and limonene presented external modifications, suggesting that these compounds penetrated the cell envelope and altered its structure.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingnone given

    B. thermosphacta exhibited evident alterations after treatment with cinnamaldehyde, limonene and eugenol; eugenol often induced swelling and occasionally disrupted the external envelope.

    “B. thermosphacta exhibited evident alterations after treatment with cinnamaldehyde, limonene and eugenol; eugenol often induced swelling and occasionally disrupted the external envelope.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingcitation

    After 24 h of treatment with mint essential oil, cellular damage of rod bacteria was observed, whereas the damage was less evident in coccoid bacteria.

    “After 24 h of treatment with the EO of mint, cellular damage of rod bacteria was observed by Hafedh et al. [110], whereas the damage was less evident in coccoid bacteria.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [110] Hafedh, 2009, Biological activities of the essential oils and methanol extract of two cultivated mint species (Mentha longifolia and Mentha pulegium) used in the Tunisian folkloric medicine, World J. Biotec. Microbiol. source

      Not checked in the free run.

  • May combine two claims.

    Findingcitation

    The activity of essential oils and/or their components differs depending on the shape of the bacteria studied, and rod-shaped bacterial cells are more sensitive to essential oils than coccoid cells.

    “The activity of EOs and/or their components differs depending on the shape of the bacteria studied, and rod shaped bacterial cells have been reported to be more sensitive to EOs than coccoid cells.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [110] Hafedh, 2009, Biological activities of the essential oils and methanol extract of two cultivated mint species (Mentha longifolia and Mentha pulegium) used in the Tunisian folkloric medicine, World J. Biotec. Microbiol. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingnone given

    Volatile organic compounds produced by the rhizospheric bacteria Pseudomonas fluorescens B-4117 and Serratia plymuthica IC1270 may inhibit the cell-cell communication QS network mediated by AHL signalling molecules produced by various bacteria, such as Agrobacterium, Chromobacterium, Pectobacterium and Pseudomonas.

    “Volatile organic compounds, such as those produced by the rhizospheric bacteria Pseudomonas fluorescens B-4117 and Serratia plymuthica IC1270, may inhibit the cell-cell communication QS network mediated by AHL signalling molecules produced by various bacteria, such as Agrobacterium, Chromobacterium, Pectobacterium and Pseudomonas.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingcitation

    The essential oils of lavender, roses, geraniums, cloves and rosemary are able to inhibit QS, whereas orange and juniper essential oils appear to have no anti-QS properties.

    “The EOs of lavender, roses, geraniums, cloves and rosemary are also able to inhibit QS, whereas orange and juniper EOs appear to have no anti-QS properties [126,127,128,129,130,131].”
    Quote in the paperNot a substantial claim0 of 6 sources checked
    • cites [126] Méndez-Vilas, A. (2011). Science Against Microbial Pathogens: Communicating Current Research and Technological Advances, Brown Walker Press.

      Not checked in the free run.

    • cites [127] Cox, 2005, Effects of a topical essential oil-containing formulation on bio-film-forming coagulase-negative staphylococci, Lett. Appl. Microbiol. source

      Not checked in the free run.

    • cites [128] Khan, 2009, Inhibition of quorum sensing regulated bacterial functions by plant essential oils with special reference to clove oil, Lett. Appl. Microbiol. source

      Not checked in the free run.

    • cites [129] Zaki, 2013, Assessment of anti-quorum sensing activity for some ornamental and medicinal plants native to Egypt, Sci. Pharm. source

      Not checked in the free run.

    • cites [130] Varga, 2010, Inhibition of quorum-sensing signals by essential oils, Phytother. Res. source

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    • cites [131] Chernin, 1998, Chitinolytic activity in Chromobacterium violaceum: Substrate analysis and regulation by quorum sensing, J. Bacteriol. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    The exchange between the hydroxyl group and a methyl ether in carvacrol can affect its hydrophobicity and antimicrobial activity.

    “The exchange between the hydroxyl group and a methyl ether in carvacrol can affect its hydrophobicity and antimicrobial activity.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    trans-Cinnamaldehyde can inhibit the growth of E. coli and S. typhimirium without disintegrating the outer membrane or depleting intracellular ATP.

    “For instance, trans-cinnamaldehyde can inhibit the growth of E. coli and S. typhimirium without disintegrating the OM or depleting intracellular ATP.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [13] Helander, 1998, Characterization of the action of selected essential oil components on Gram-negative bacteria, J. Agric. Food Chem. source

      Not checked in the free run.

    • cites [14] Helander, 1997, Polyethyleneimine is an effective permeabilizer of Gram negative bacteria, Microbiology source

      Not checked in the free run.

  • May combine two claims.

    Premisenone given

    Thymol and carvacrol have similar antimicrobial effects but different mechanisms of action against Gram-positive and Gram-negative bacteria.

    “For instance, thymol and carvacrol have similar antimicrobial effects but have different mechanisms of action against Gram-positive and Gram-negative bacteria.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisenone given

    The antimicrobial activity of most terpenoids is related to their functional groups, and the hydroxyl group of phenolic terpenoids and delocalised electrons are important for antimicrobial action.

    “The antimicrobial activity of most terpenoids is related to their functional groups, and the hydroxyl group of the phenolic terpenoids and the presence of delocalised electrons are important elements for their antimicrobial action.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Carvone is ineffective against the outer membrane and does not affect the cellular ATP pool.

    “Carvone is also ineffective against the OM and does not affect the cellular ATP pool [13,14].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [13] Helander, 1998, Characterization of the action of selected essential oil components on Gram-negative bacteria, J. Agric. Food Chem. source

      Not checked in the free run.

    • cites [14] Helander, 1997, Polyethyleneimine is an effective permeabilizer of Gram negative bacteria, Microbiology source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The effect of phenolic compounds depends on concentration: at low concentrations they interfere with energy-producing enzymes, and at higher concentrations they denature proteins.

    “Their effect depends on the amount of the compound present; at low concentrations, they can interfere with enzymes involved in the production of energy, and at higher concentrations, they can denature proteins [7].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [7] Tiwari, 2009, Application of natural antimicrobials for food preservation, J. Agric. Food Chem. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The antimicrobial activity of limonene and p-cymene depends on the alkyl group, and limonene can be more effective than p-cymene.

    “The antimicrobial activity of other molecules, such as limonene and p-cymene, depends on the alkyl group. Thus, in some cases, limonene can be considered to be more effective than p-cymene [12].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [12] Dorman, 2000, Antimicrobial agents from plants: Antibacterial activity of plant volatile oils, J. Appl. Microbiol. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The outer membrane is almost but not totally impermeable to hydrophobic molecules, some of which can slowly traverse through porins.

    “The OM is, however, almost but not totally impermeable to hydrophobic molecules, some of which can slowly traverse through porins [10,11].”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [10] Plesiat, 1992, Outer membranes of Gram-negative bacteria are permeable to steroid probes, Mol. Microbiol. source

      Not checked in the free run.

    • cites [11] Neidhardt, F.C. (1996). Escherichia coli and Salmonella: Cellular and Molecular biology, ASM Press.

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Small hydrophilic solutes pass through the outer membrane via porin proteins, which is one reason Gram-negative bacteria are relatively resistant to hydrophobic antibiotics and toxic drugs.

    “Small hydrophilic solutes are able to pass through the OM via abundant porin proteins that serve as hydrophilic transmembrane channels, and this is one reason that Gram-negative bacteria are relatively resistant to hydrophobic antibiotics and toxic drugs [8,9].”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [8] Nikaido, 1994, Prevention of drug access to bacterial targets: Permeability barriers and active efflux, Science source

      Not checked in the free run.

    • cites [9] Vaara, 1992, Agents that increase the permeability of the outer membrane, Microbiol. Rev. source

      Not checked in the free run.

  • May combine two claims.

    Premisenone given

    Essential oils and their components act against a variety of targets, particularly the membrane and cytoplasm, and in some cases completely change cell morphology.

    “The EOs and their components have a variety of targets, particularly the membrane and cytoplasm, and in certain situations, they completely alter the morphology of the cells.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    p-Cymene does not affect membrane permeability but may decrease the enthalpy and melting temperature of the membrane.

    “p-Cymene does not affect the membrane permeability but may decrease the enthalpy and melting temperature of membrane [24]; these properties strengthen the notion that this compound may act as a substitutional impurity in the membrane.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [24] Cristani, 2007, Interaction of four monoterpenes contained in essential oils with model membranes:implications for their antibacterialactivity, J. Agric. Food Chem. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Vanillin's primary target is the membrane, but other targets may be present within the microbial cell.

    “Fitzgerald et al. [49] observed that vanillin’s primary target is the membrane but reported that other targets may be present within the microbial cell.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [49] Fitzgerald, 2005, Structure-function analysis of the vanillin molecule and its antifungal properties, J. Agric. Food Chem. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Isoeugenol is more active against bacteria than eugenol and is also effective against yeasts and moulds.

    “Isoeugenol is more active against bacteria than eugenol and is also effective against yeasts and moulds [39,42,43].”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [39] Laekeman, 1990, Eugenol a valuable compound for in vitro experimental research and worthwhile for further in vivo investigation, Phytother. Res. source

      Not checked in the free run.

    • cites [42] Zemek, 1979, Antibiotic properties of lignin components, Folia Microbiol. source

      Not checked in the free run.

    • cites [43] Zemek, 1987, Antimicrobial properties of aromatic compounds of plant origin, Folia Microbiol. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The antimicrobial activity of phenylpropenes depends on the type and number of substitutions on the aromatic ring and on the microbial strain and conditions in which the essential oil is tested.

    “The antimicrobial activity of the phenylpropenes also depends on the type and number of substitutions on the aromatic ring and similar to most other EOs, on the microbial strain and conditions in which the EO is tested [41].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [41] Pauli, 2010, Antimicrobial properties of volatile phenylpropanes, Nat. Prod. Commun.

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The activity of carvacrol seems to be linked to the presence of a hydroxyl group that may function as a trans-membrane carrier of monovalent cations by carrying H+ into the cell cytoplasm and transporting K+ back out.

    “The activity of carvacrol seems to be linked to the presence of a hydroxyl group that may function as a trans-membrane carrier of monovalent cations by carrying H+ into the cell cytoplasm and transporting K+ back out [18,19].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [18] Ultee, 2002, The phenolic hydroxyl group of carvacrol is essential for action against the food-borne pathogen Bacillus cereus, Appl. Environ. Microbiol. source

      Not checked in the free run.

    • cites [19] Combes, 2006, Antimicrobial activity of carvacrol related to its chemical structure, Lett. Appl. Microbiol. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    p-Cymene did not affect protein synthesis in E. coli but did affect the membrane potential.

    “Burt et al. [25] demonstrated that although the compound did not affect protein synthesis in E. coli, it did affect the membrane potential.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [25] Burt, 2007, Carvacrol induces heat shock protein and inhibits synthesis of flagellin in Escherichia coli O157:H7, Appl. Environ. Microbiol. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Carvacrol causes the release of lipopolysaccharides and acts on the cytoplasmic membrane to alter the transport of ions.

    “It causes the release of LPS [13] and also acts on cytoplasmic membrane to alter the transport of ions.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [13] Helander, 1998, Characterization of the action of selected essential oil components on Gram-negative bacteria, J. Agric. Food Chem. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Even cells with flagella exhibited decreased motility that depended on the amount of carvacrol, indicating that carvacrol also diminished the proton motive force needed to drive flagellar movement.

    “However, even cells with flagella exhibited decreased motility that was depended upon the amount of carvacrol, indicating that the compound also diminished the proton motive force needed to drive flagellar movement [38].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [38] Gabel, 2003, The speed of the flagellar rotary motor of Escherichia coli varies linearly with proton motive force, Proc. Natl. Acad. Sci. USA source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    p-Cymene shows a high affinity for microbial membranes and can perturb the membranes, causing them to expand and affecting the membrane potential of intact cells.

    “p-Cymene shows a high affinity for microbial membranes and can perturb the membranes, causing them to expand and affecting the membrane potential of intact cells [18].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [18] Ultee, 2002, The phenolic hydroxyl group of carvacrol is essential for action against the food-borne pathogen Bacillus cereus, Appl. Environ. Microbiol. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    There is limited evidence that carvacrol affects periplasmic enzymes and membrane proteins, and it may also have intracellular targets.

    “There is also limited evidence that carvacrol affects periplasmic enzymes and membrane proteins [30], and it may also have intracellular targets [37].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [30] Juven, 1994, Factors that Interact with the antibacterial action of thyme essential oil and its active constituents, J. Appl. Bacteriol. source

      Not checked in the free run.

    • cites [37] Kocsis, 2009, Effect of thyme (Thymus vulgaris L.) essential oil and its main constituents on the outer membrane protein composition of Erwinia strains studied with microfluid chip technology, Chromatographia source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Cinnamaldehyde is generally less powerful than eugenol, but against E. coli and S. typhimurium its activity is similar to thymol and carvacrol.

    “Cinnamaldehyde is generally less powerful than eugenol [45], but when it is used against E. coli and S. typhimurium, its activity is similar to thymol and carvacrol, the most potent EOs [13].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [45] Gill, 2004, Mechanisms of bactericidal action of cinnamaldehyde against Listeria monocytogenes and of eugenol against L. monocytogenes and Lactobacillus sakei, Appl. Environ. Microbiol. source

      Not checked in the free run.

    • cites [13] Helander, 1998, Characterization of the action of selected essential oil components on Gram-negative bacteria, J. Agric. Food Chem. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    A sub-lethal concentration of cinnamaldehyde does not affect the integrity of the membrane in E. coli but can inhibit the growth and bioluminescence of Photobacterium leiognathi, suggesting it gains access to the periplasm and perhaps cytoplasm.

    “For example, a sub-lethal concentration of the molecule does not affect the integrity of the membrane in E. coli but can inhibit the growth and bioluminescence of the microorganism Photobacterium leiognathi; this suggests that cinnamaldheyde gains access to the periplasm and perhaps also to the cytoplasm [13].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [13] Helander, 1998, Characterization of the action of selected essential oil components on Gram-negative bacteria, J. Agric. Food Chem. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Carvacrol inhibited the synthesis of flagellin and gave rise to cells without flagella that subsequently exhibited decreased motility.

    “Carvacrol also inhibited the synthesis of another microbial protein, flagellin, and gave rise to cells without flagella that subsequently exhibited decreased motility.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [25] Burt, 2007, Carvacrol induces heat shock protein and inhibits synthesis of flagellin in Escherichia coli O157:H7, Appl. Environ. Microbiol. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Vanillin inhibits the respiration pathway in E. coli and L. innocua and has activity against some lactic acid bacteria, such as L. plantarum, by disrupting K+ and pH homeostasis.

    “However, some studies have shown that it inhibits the respiration pathway in E. coli and L. innocua and that it has activity against some lactic acid bacteria, such as L. plantarum, by disrupting K+ and pH homeostasis [48].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [48] Fitzgerald, 2004, Mode of antimicrobial of vanillin against Escherichia coli, Lactobacillus plantarum and Listeria innocua, J. Appl. Microbiol. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Thymol can induce the release of lipopolysaccharides but does not affect chelating cations.

    “In some cases, thymol can induce the release of lipopolysaccharides, but it does not affect chelating cations [13].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [13] Helander, 1998, Characterization of the action of selected essential oil components on Gram-negative bacteria, J. Agric. Food Chem. source

      Not checked in the free run.

  • May combine two claims.

    Premisenone given

    Cinnamaldehyde has at least three mechanisms of action against bacteria: at low concentrations it inhibits enzymes involved in cytokine interactions or other less important cell functions; at higher concentrations it acts as an ATPase inhibitor; at lethal concentration it perturbs the membrane.

    “Cinnamaldehyde has at least three mechanisms of action against bacteria. At low concentrations, it inhibits enzymes involved in cytokine interactions or other less important cell functions, and at higher concentrations, it acts as an ATPase inhibitor. At a lethal concentration, cinnamaldheyde perturbs the membrane.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    The interaction of thymol with the membrane affects membrane permeability and results in the release of K+ ions and ATP.

    “The interaction of thymol with the membrane affects membrane permeability and results in the release of K+ ions and ATP [20,27,28].”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [20] Lambert, 2001, A study of the minimum inhibitory concentration and mode of action of oregano essential oil, thymol and carvacrol, J. Appl. Microbiol. source

      Not checked in the free run.

    • cites [27] Walsh, 2003, Activity and mechanisms of action of selected biocidal agents on Gram-positive and-negative bacteria, J. Appl. Microbiol. source

      Not checked in the free run.

    • cites [28] Xu, 2008, The antibacterial mechanism of carvacrol and thymol against Escherichia coli, Lett. Appl. Microbiol. source

      Not checked in the free run.

  • May combine two claims.

    Premisenone given

    Eugenol alters the membrane, affects the transport of ions and ATP and changes the fatty acid profile of different bacteria.

    “Eugenol alters the membrane, affects the transport of ions and ATP and changes the fatty acid profile of different bacteria.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    E. coli cells grown in the presence of a sub-lethal concentration of carvacrol produced significantly more GroEL, indicating that carvacrol affected protein folding.

    “Burt et al. [25] showed that E. coli cells grown in the presence of a sub-lethal concentration of carvacrol produced significantly more GroEL, indicating that carvacrol affected protein folding.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [25] Burt, 2007, Carvacrol induces heat shock protein and inhibits synthesis of flagellin in Escherichia coli O157:H7, Appl. Environ. Microbiol. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Thymol antimicrobial activity results in structural and functional alterations in the cytoplasmic membrane that can damage the outer and inner membranes and interact with membrane proteins and intracellular targets.

    “Similar to carvacrol, thymol antimicrobial activity results in structural and functional alterations in the cytoplasmic membrane [26] that can damage the outer and inner membranes; it can also interact with membrane proteins and intracellular targets.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [26] Sikkema, 1995, Mechanisms of membrane toxicity of hydrocarbons, Microbiol. Rev. source

      Not checked in the free run.

  • May combine two claims.

    Premisenone given

    Thymol integrates within the polar head-groups of the lipid bilayer, inducing alterations of the cell membrane.

    “Thymol integrates within the polar head-groups of the lipid bilayer, inducing alterations of the cell membrane.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Treatment with p-cymene resulted in decreased cellular motility because the proton motive force is required for flagellar movement.

    “Treatment with p-cymene resulted in decreased cellular motility because the proton motive force is required for flagellar movement.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [25] Burt, 2007, Carvacrol induces heat shock protein and inhibits synthesis of flagellin in Escherichia coli O157:H7, Appl. Environ. Microbiol. source

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    The mechanisms of essential oil action include chemical modifications of the cell membrane, cytoplasm, enzymes and proteins, and can completely change the conformation of the microbial cell.

    “These mechanisms include chemical modifications of the cell membrane, cytoplasm, enzymes and proteins, and they can completely change the conformation of the microbial cell.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [70] Carson, 2002, Mechanism of action of Melaleuca alternifolia (tea tree) oil on Staphylococcus aureus determined by time-kill, lysis, leakage, and salt tolerance assays and electron microscopy, Antimicrob. Agents Chemother. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Carvone was ineffective against the outer membrane of E. coli and S. typhimurium and did not affect their intracellular ATP pool.

    “In contrast, another study [13] found that carvone was ineffective against the OM of E. coli and S. typhimurium and did not affect their intracellular ATP pool.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [13] Helander, 1998, Characterization of the action of selected essential oil components on Gram-negative bacteria, J. Agric. Food Chem. source

      Not checked in the free run.

  • May combine two claims.

    Premisenone given

    The effects of essential oils usually lead to destabilisation of the phospholipid bilayer, destruction of plasma membrane function and composition, loss of vital intracellular components and inactivation of enzymatic mechanisms.

    “The effects of EOs usually lead to the destabilisation of the phospholipid bilayer, the destruction of the plasma membrane function and composition, the loss of vital intracellular components and the inactivation of enzymatic mechanisms.”
    Quote in the paperNot a substantial claim

  • May combine two claims. The quote only partly states this claim.

    Premisecitation

    The mechanisms of action of essential oils include degradation of the cell wall, damaging the cytoplasmic membrane, cytoplasm coagulation, damaging membrane proteins, increased permeability leading to leakage of cell contents, reducing the proton motive force, reducing the intracellular ATP pool, and reducing the membrane potential.

    “In fact, the mechanisms of action of the EOs include the degradation of the cell wall [13,64], damaging the cytoplasmic membrane, cytoplasm coagulation [18,33,65], damaging the membrane proteins, increased permeability leading to leakage of the cell contents [20,30]”
    Quote in the paperNot a substantial claim0 of 7 sources checked
    • cites [13] Helander, 1998, Characterization of the action of selected essential oil components on Gram-negative bacteria, J. Agric. Food Chem. source

      Not checked in the free run.

    • cites [64] Gill, 2006, Disruption of E. coli, Listeria monocytogenes and Lactobacillus sakei cellular membranes by plant oil aromatics, Int. J. Food Microbiol. source

      Not checked in the free run.

    • cites [18] Ultee, 2002, The phenolic hydroxyl group of carvacrol is essential for action against the food-borne pathogen Bacillus cereus, Appl. Environ. Microbiol. source

      Not checked in the free run.

    • cites [33] Ultee, 2000, Adaptation of the food-borne pathogen Bacillus cereus to carvacrol, Arch. Microbiol. source

      Not checked in the free run.

    • cites [65] Gustafson, 1998, Effects of tea tree oil on Escherichia coli, Lett. Appl. Microbiol. source

      Not checked in the free run.

    • cites [20] Lambert, 2001, A study of the minimum inhibitory concentration and mode of action of oregano essential oil, thymol and carvacrol, J. Appl. Microbiol. source

      Not checked in the free run.

    • cites [30] Juven, 1994, Factors that Interact with the antibacterial action of thyme essential oil and its active constituents, J. Appl. Bacteriol. source

      Not checked in the free run.

  • May combine two claims.

    Premisenone given

    In general, essential oils act to inhibit the growth of bacterial cells and also inhibit the production of toxic bacterial metabolites.

    “In general, EOs act to inhibit the growth of bacterial cells and also inhibit the production of toxic bacterial metabolites.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisereasoning

    Essential oils can alter both the permeability and function of membrane proteins.

    “The EOs can alter both the permeability and function of membrane proteins.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Some essential oils, such as those from basil, sage, hyssop, rosemary, oregano and marjoram, are active against E. coli, S. aureus, B. cereus and Salmonella spp. but are less effective against Pseudomonas spp. due to exopolysaccharide formation that increases resistance.

    “Some EOs, such as those found in basil, sage, hyssop, rosemary, oregano and marjoram, are active against E. coli, S. aureus, B. cereus and Salmonella spp. but are less effective against Pseudomonas spp. due to the formation of exopolysaccharides that increase resistance to EOs [5,57].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [5] Nazzaro, 2009, Chemical composition and in vitro antimicrobial and mutagenic activities of seven lamiaceae essential oils, Molecules source

      Not checked in the free run.

    • cites [57] Burt, 2004, Essential oils: their antibacterial properties and potential applications in foods—A review, Int. J. Food Microbiol. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Tea tree oil induced damage to cell membrane structures accompanied by decreased viability for all three microorganisms in the study, and membrane damage was confirmed as the most likely cause of cell death.

    “Tea tree oil induced damage to the cell membrane structures that was accompanied by decreased viability for all three microorganisms included in their study, and the membrane damage was confirmed as the most likely cause of cell death.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [13] Helander, 1998, Characterization of the action of selected essential oil components on Gram-negative bacteria, J. Agric. Food Chem. source

      Not checked in the free run.

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    With increasing amount of carvone, the growth rate of E. coli, Streptococcus thermophilus and L. lactis decreased, and it was hypothesised that carvone might act by disturbing the metabolic energy status of cells.

    “With increasing amount of carvone, Oosterhaven et al. [50] observed a decrease in the growth rate of E. coli, Streptococcus thermophilus and L. lactis and hypothesised that the compound might act by disturbing the metabolic energy status of cells.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [50] Oosterhaven, 1995, S-carvone as a natural potato sprout inhibiting, fungistatic and bacteristatic compound, Ind. Crops Prod. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Alteration of membrane permeability and defects in the transport of molecules and ions result in a disbalance within the microbial cell, subsequently leading to cytoplasm coagulation, denaturation of several enzymes and cellular proteins, and loss of metabolites and ions.

    “The alteration of membrane permeability and the defects in the transport of molecules and ions result in a “disbalance” within the microbial cell. This subsequently leads to cytoplasm coagulation, the denaturation of several enzymes and of cellular proteins and the loss of metabolites and ions [4].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [4] Burt, 2003, Antibacterial activity of selected plant essential oils against Escherichia coli O157:H7, Lett. Appl. Microbiol. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisenone given

    Many antimicrobial compounds are constitutively expressed by plants, and others can be synthesised as a mechanism of self-defence in response to pathogens.

    “Many of the antimicrobial compounds are constitutively expressed by the plants, and others can be synthesised as mechanism of self-defence in response to pathogens.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    γ-Terpinene does not affect the growth of S. typhimurium, whereas α-terpinene inhibited 11 of the 25 bacterial species screened by Dorman and Deans.

    “γ-Terpinene does not affect the growth of S. typhimurium [30], whereas α-terpinene inhibited 11 of the 25 bacterial species screened by Dorman and Deans [12].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [30] Juven, 1994, Factors that Interact with the antibacterial action of thyme essential oil and its active constituents, J. Appl. Bacteriol. source

      Not checked in the free run.

    • cites [12] Dorman, 2000, Antimicrobial agents from plants: Antibacterial activity of plant volatile oils, J. Appl. Microbiol. source

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    The Gram-negative cell wall does not allow for the entrance of hydrophobic molecules as readily as Gram-positive bacteria; thus, essential oils are less able to affect the cell growth of Gram-negative bacteria.

    “The Gram-negative cell wall does not allow for the entrance of hydrophobic molecules as readily as Gram-positive bacteria; thus, EOs are less able to affect the cell growth of the Gram-negative bacteria [4].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [4] Burt, 2003, Antibacterial activity of selected plant essential oils against Escherichia coli O157:H7, Lett. Appl. Microbiol. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Most essential oils have a more powerful effect on Gram-positive bacteria than Gram-negative species, most likely due to differences in cell membrane compositions.

    “Most EOs have a more powerful effect on Gram-positive bacteria than Gram-negative species, and this effect is most likely due to differences in the cell membrane compositions (Figure 1) [3,56,58].”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [3] Chorianopoulos, 2008, Disinfectant test against monoculture and mixed-culture biofilms composed of technological, spoilage and pathogenic bacteria: Bactericidal effect of essential oil and hydrosol of Satureja thymbra and comparison with standard acid-base sanitizers, J. Appl. Microbiol. source

      Not checked in the free run.

    • cites [56] Gutierrez, 2008, The anti-microbial efficacy of plant essential oil combinations and interactions with food ingredients, Int. J. Food Microbiol. source

      Not checked in the free run.

    • cites [58] Marino, 2001, Antimicrobial activity of the essential oils of Thymus vulgaris L. measured using a bioimpedimetric method, Int. J. Food Microbiol. source

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    Different components of essential oils can act on proteins present in bacteria and may affect cell division.

    “Different components of EOs can act on proteins present in bacteria and may affect cell division.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    Down-regulation of H-NS and L7/L12 increases bacterial DNA stability and inhibits transcription as a further mechanism of protection.

    “This increases bacterial DNA stability and inhibits the transcription as further mechanism of protection.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    YidC is an evolutionarily conserved protein that is required for the growth of E. coli.

    “YidC represents an evolutionarily conserved protein that is required for the growth of E. coli [88,89].”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [88] Serek, 2004, Escherichia coli YidC is a membrane insertase for Sec-independent proteins, EMBO J. source

      Not checked in the free run.

    • cites [89] Samuelson, 2000, YidC mediates membrane protein insertion in bacteria, Nature source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    Increased outer membrane permeability results in the dispersion of desaturase enzymes and allows them to act on membrane fatty acids.

    “This results in the dispersion of the desaturase enzymes and allows them to act on the membrane fatty acids.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationcitation

    Adaptation of cells to essential oils at concentrations lower than the MIC could increase the percentage of UFAs responsible for membrane fluidity, indicating a mechanism of action against the outer cell envelope that could cause membrane structural alterations observable by SEM.

    “The adaptation of the cells to the presence of these compounds at a concentration lower than the MIC could result in an increase in the percentage of UFAs responsible for the fluidity of the membrane [35,71], which may indicate a certain mechanism of action against the outer cell envelope that could cause membrane structural alterations observable by SEM.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [35] Betts, 2007, Membrane toxicity of antimicrobial compounds from essential oils, J. Agric. Food Chem. source

      Not checked in the free run.

    • cites [71] Heath, 2004, Fatty acid biosynthesis as a target for novel antibacterials, Curr. Opin. Invest. Drugs

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    Other intracellular events may contribute to the intracellular ATP decrease, such as loss of inorganic phosphate through a compromised permeable membrane or disruption of the proton motive force and changes in the balance of essential ions such as K+ and H+.

    “Other intracellular events may contribute to the intracellular ATP decrease; for example, inorganic phosphate may have been lost by passing through the compromised permeable membrane [93,94,95,96,97], or the proton motive force and changes in the balance of some essential ions, such as K+ and H+, may have been disrupted [36].”
    Quote in the paperNot a substantial claim0 of 6 sources checked
    • cites [93] Turgis, 2009, Antimicrobial activity of mustard essential oil against Escherichia coli O157:H7 and Salmonella typhi, Food Control. source

      Not checked in the free run.

    • cites [94] Caillet, 2009, Effect of gamma radiation and oregano essential oil on murein and ATP concentration of Staphylococcus aureus, J. Food Sci. source

      Not checked in the free run.

    • cites [95] Caillet, 2006, Effect of gamma radiation and oregano essential oil on murein and ATP concentration of Listeria monocytogenes, J. Food Prot. source

      Not checked in the free run.

    • cites [96] Abee, 1994, Kinetic studies of the action of lactacin F, a bacteriocin produced by Lactobacillus johnsonii that forms poration complexes in the cytoplasmic membrane, Appl. Env. Microbiol. source

      Not checked in the free run.

    • cites [97] Shabala, 2002, Responses of Listeria monocytogenes to acid stress and glucose availability revealed by a novel combination of fluorescence microscopy and microelectrode ion-selective techniques, Appl. Env. Microbiol. source

      Not checked in the free run.

    • cites [36] Ultee, 1999, Mechanisms of action of carvacrol on the food-borne pathogen, Appl. Environ. Microbiol. source

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    The activity of essential oils and/or their components is not attributable to a single event; most components act on the outer membrane and increase its permeability.

    “Again, the activity of the EOs and/or their components is not attributable to a single event; most of the components of the EOs [13,18,48] act on the OM and increase its permeability.”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [13] Helander, 1998, Characterization of the action of selected essential oil components on Gram-negative bacteria, J. Agric. Food Chem. source

      Not checked in the free run.

    • cites [18] Ultee, 2002, The phenolic hydroxyl group of carvacrol is essential for action against the food-borne pathogen Bacillus cereus, Appl. Environ. Microbiol. source

      Not checked in the free run.

    • cites [48] Fitzgerald, 2004, Mode of antimicrobial of vanillin against Escherichia coli, Lactobacillus plantarum and Listeria innocua, J. Appl. Microbiol. source

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    Partitioning of cyclic monoterpenes into membranes results in membrane expansion, increased membrane fluidity and the inhibition of a membrane-embedded enzyme.

    “This results in membrane expansion, increased membrane fluidity and the inhibition of a membrane-embedded enzyme.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [26] Sikkema, 1995, Mechanisms of membrane toxicity of hydrocarbons, Microbiol. Rev. source

      Not checked in the free run.

    • cites [114] Sikkema, 1994, Cellular toxicity of lipophilic compounds: Mechanisms, implications, and adaptations, Biocatalysis source

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    The morphology of Gram-negative cells was much more affected by carvacrol than Gram-positive cells due to the presence of an outer membrane in Gram-negative bacteria and the fact that biological membranes are among the possible targets of carvacrol.

    “The morphology of the Gram-negative cells was much more affected by carvacrol than the Gram-positive cells due to the presence of an OM in the Gram-negative bacteria and the fact that biological membranes are among the possible targets of carvacrol.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [120] Alakomi, 2006, Weakening effect of cell permeabilizer on gram-negative bacteria causing biodeterioration, Appl. Environ. Microbiol. source

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    Eugenol may be capable of disrupting the membrane and allowing the leakage of intracellular constituents, while other compounds may only cause structural alterations of the outer envelope.

    “This suggests that eugenol may be capable of disrupting the membrane and allowing the leakage of intracellular constituents, while the other compounds may only cause structural alterations of the outer envelope.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [35] Betts, 2007, Membrane toxicity of antimicrobial compounds from essential oils, J. Agric. Food Chem. source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    This mechanism may cause the inhibition of ATPase activity, as well as the inhibition of other enzymes and altered bacterial growth.

    “This mechanism may cause the inhibition of ATPase activity, as well as the inhibition of other enzymes and altered bacterial growth [13,27,47,96,98].”
    Quote in the paperNot a substantial claim0 of 5 sources checked
    • cites [13] Helander, 1998, Characterization of the action of selected essential oil components on Gram-negative bacteria, J. Agric. Food Chem. source

      Not checked in the free run.

    • cites [27] Walsh, 2003, Activity and mechanisms of action of selected biocidal agents on Gram-positive and-negative bacteria, J. Appl. Microbiol. source

      Not checked in the free run.

    • cites [47] Wendakoon, 1995, Inhibition of amino acid decarboxylase activity of Enterobacter aerogenes by active components in spices, J. Food Prot. source

      Not checked in the free run.

    • cites [96] Abee, 1994, Kinetic studies of the action of lactacin F, a bacteriocin produced by Lactobacillus johnsonii that forms poration complexes in the cytoplasmic membrane, Appl. Env. Microbiol. source

      Not checked in the free run.

    • cites [98] Kwon, 2003, Bactericidal effects and inhibition of cell separation of cinnamic aldehyde on Bacillus cereus, Lett. Appl. Microbiol. source

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    When E. coli cells were treated with carvacrol, the glycolytic pathway modified the amounts of formate and succinate, which together with citrate indicates a shift from respiration to fermentation and K+ leakage.

    “When E. coli cells were treated with carvacrol, the glycolytic pathway modified the amounts of formate and succinate, two organic acids that are normally present in the Krebs cycle, which together with citrate, indicates a shift from respiration to fermentation and K+ leakage [108].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [108] Cox, 1998, Tea tree oil causes K+ leakage and inhibits respiration in Escherichia coli, Lett. Appl. Microbiol. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    Differences in the response of bacterial species to cinnamaldehyde may be due to differences in the ability of this small hydrophobic molecule to interact with the outer surface of the cells and thus gain access to the cell membrane.

    “A possible explanation for the difference in the behaviour of the three bacterial species in response to cinnamaldehyde is that there may be differences in the ability of this small hydrophobic molecule to interact with the outer surface of the cells and thus gain access to the cell membrane.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    Bacteria coordinate both bacterium-bacterium interactions and associations with higher organisms through intercellular communication systems known as quorum sensing (QS) systems.

    “Bacteria coordinate both bacterium-bacterium interactions and associations with higher organisms through intercellular communication systems known as quorum sensing (QS) systems.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Bacterial QS may be inhibited through different mechanisms, including inhibition of AHL synthesis, inhibition of AHL transport and/or secretion, sequestration of AHLs, antagonistic action, and inhibition of targets downstream of AHL receptor binding.

    “Bacterial QS may be inhibited through different mechanisms, including (1) the inhibition of AHL synthesis, (2) the inhibition of AHL transport and/or secretion, (3) the sequestration of AHLs, (4) the antagonistic action and (5) the inhibition of targets downstream of AHL receptor binding [125].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [125] Nazzaro, 2013, Quorum sensing and phytochemicals, Int. J. Mol. Sci. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    The expression of QS genes results in the production of chemical signalling molecules known as autoinducers or bacterial pheromones.

    “The expression of the QS genes results in the production of chemical signalling molecules that are known as autoinducers or bacterial pheromones.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The accumulation of a stimulatory amount of QS molecules can occur only when a specific number of cells, referred to as a quorum, are present.

    “The accumulation of a stimulatory amount of the QS molecules can occur only when a specific number of cells, referred to as a quorum, are present [121].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [121] Bassler, 2002, Small talk: Cell-to-cell communication in bacteria, Cell source

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    The activity of plant extracts can be strain-specific and may depend on the QS molecule involved.

    “again demonstrating that the activity of plant extracts can be strain-specific and may depend on the QS molecule involved.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [132] Niu, 2006, Subinhibitory concentrations of cinnamaldehyde interfere with quorum sensing, Lett. Appl. Microbiol. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisereasoning

    Autoinducers are produced as the bacterial population grows until a threshold concentration perceived by the bacteria is reached, resulting in the activation or repression of specific genes.

    “These molecules are produced as the bacterial population grows until a threshold concentration perceived by the bacteria is reached, resulting in the activation or repression of specific genes.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationcitation

    The modified structure of the Gram-negative cell surface could be interpreted as an adaptive response to stress; nearly all of the Gram-negative bacteria examined demonstrated a greater increase of roughness after carvacrol treatment compared with Gram-positive bacteria.

    “The modified structure of the Gram-negative cell surface could also be interpreted as an adaptive response to stress; in fact, nearly all of the Gram-negative bacteria examined demonstrated greater increase of roughness after carvacrol treatment compared with Gram-positive bacteria.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [120] Alakomi, 2006, Weakening effect of cell permeabilizer on gram-negative bacteria causing biodeterioration, Appl. Environ. Microbiol. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    QS-controlled behaviours occur only when bacteria reach a specific cell density.

    “QS-controlled behaviours occur only when bacteria reach a specific cell density.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisereasoning

    QS behaviours are unproductive if undertaken by a singular bacterium but become effective when the action is simultaneously performed by a group of bacteria.

    “These behaviours are unproductive if undertaken by a singular bacterium but become effective when the action is simultaneously performed by a group of bacteria.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    QS can regulate a number of activities, such as virulence factor expression, bioluminescence, sporulation, biofilm formation and mating.

    “QS can regulate a number of activities, such as virulence factor expression, bioluminescence, sporulation, biofilm formation and mating.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Interpretationcitation

    Essential oils may represent the richest available reservoir of novel therapeutics.

    “EOs may represent the richest available reservoir of novel therapeutics [122,123,124].”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [122] Hentzer, 2003, Pharmacological inhibition of quorum sensing for the treatment of chronic bacterial infections, J. Clin. Invest. source

      Not checked in the free run.

    • cites [123] Lewis, 2006, Prospects of plant derived antibacterials, Nat. Biotechnol. source

      Not checked in the free run.

    • cites [124] Kumar, 2006, Search for antibacterial and antifungal agents from selected Indian medicinal plants, J. Ethnopharmacol. source

      Not checked in the free run.

95 of 95

  • The paper relies on this without support.

    The cell wall of Gram-positive bacteria consists of approximately 90%–95% peptidoglycan.

    “Approximately 90%–95% of the cell wall of Gram-positive bacteria consists of peptidoglycan, to which other molecules, such as teicoic acid and proteins, are linked (Figure 1).”

  • The paper relies on this without support.

    The cell wall of Gram-negative bacteria has a peptidoglycan layer 2–3 nm thick and an outer membrane outside the peptidoglycan layer.

    “It has a peptidoglycan layer that is 2–3 nm thick, which is thinner than in the cell wall of Gram-positive bacteria, and composes approximately 20% of the dry weight of the cell. An outer membrane (OM) lies outside of the thin peptidoglycan layer.”
2 of 2

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Mustard-oil treatment names different bacteria from the reported result

    Minor

    The sentence identifies E. coli and Salmonella as the bacteria treated with mustard oil, but says the resulting ATP loss was in S. aureus. The cited reference instead concerns oregano oil and S. aureus.

  • Intracellular ATP is said to increase and to be lost after EO exposure

    Minor

    One passage says components including thymol and carvacrol increase intracellular ATP in connection with membrane destruction; another describes EO-induced membrane disruption as causing ATP to leave the cell. The opposing directions are not reconciled in the text.

2 of 2

Cites

Flagged first, then by citations

4 of the 139 references couldn’t be matched to a known paper.

Research works printed but not linked: 4

  1. Neidhardt, F.C. (1996). Escherichia coli and Salmonella: Cellular and Molecular biology, ASM Press.
  2. Caballero, B., Trugo, L.C., and Finglas, P.M. (2003). Encyclopedia of Food Sciences and Nutrition, Elsevier Academic Press. [2nd ed.].
  3. Beuchat, M.P., and Montville, L.R. (2001). Food Microbiology. Fundamentals and Frontiers, ASM Press. [2nd ed.].
  4. Méndez-Vilas, A. (2011). Science Against Microbial Pathogens: Communicating Current Research and Technological Advances, Brown Walker Press.

Cited by

Sorted by citations

Related

Authors
Nazzaro, F., Fratianni, F., De Martino, L., Coppola, R., & De Feo, V.
Affiliations
  • Institute of Food Science (IT)
  • Dipartimento di Farmacia,Via Giovanni Paolo II, 132, 84084 Fisciano (SA), Italy
  • University of Salerno (IT)
Corresponding author
Nazzaro, Filomena
ORCID
Venue
Pharmaceuticals
Publisher
MDPI AG
Published
2013-11-25
Volume
6
Issue
12
Pages
1451-1474
ISSN
1424-8247 (ISSN-L)
DOI
10.3390/ph6121451
PMC
PMC3873673
OpenAlex
W2011444187
Semantic Scholar
0f06de232fd83dfd81a58cd152cd31fe263c6b81
Cited by
2,186
References
139
Citations by year
2026: 247 · 2025: 233 · 2024: 209 · 2023: 258 · 2022: 245 · 2021: 234 · 2020: 235 · 2019: 150 · 2018: 145 · 2017: 105 · 2016: 77 · 2015: 33 · 2014: 12
FWCI
60.74
Type
journal article
Language
en
Open access
Licence
Locations
  • Pharmaceuticals (publishedVersion, cc-by)
  • Europe PMC (PubMed Central) (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • Archivio Istituzionale della Ricerca - Università degli Studi del Molise (submittedVersion)
Topics
  • Life Sciences › Agricultural and Biological Sciences › Food Science › Essential Oils and Antimicrobial Activity
  • Physical Sciences › Chemistry › Organic Chemistry › Antimicrobial agents and applications
  • Life Sciences › Agricultural and Biological Sciences › Plant Science › Insect Pest Control Strategies
Keywords
essential oils, pathogenic bacteria, antibacterial activity, antimicrobial resistance, plant secondary metabolites, biocides, bacterial membrane disruption, cell morphology, molds and yeasts

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-10.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-10.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

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