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Cited by 186Essential Oils and Antimicrobial ActivityMedicinal Plant ResearchAgricultural and Biological Research

Comparison of Techniques and Solvents on the Antimicrobial and Antioxidant Potential of Extracts from Acacia dealbata and Olea europaea

Open access
Borges, Anabela, José, Helena, Homem, Vera, Simões, Manuel·2020·Antibiotics
DOI 10.3390/antibiotics9020048PMC PMC7168226
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Abstract

Ethnopharmacological use of plant natural extracts has been known since ancient times. The optimization of plant molecule extraction is fundamental in obtaining relevant extraction yields. The main purpose of this study was to understand the role of different extraction techniques (solid-liquid, ultrasound, Soxhlet, and microwave) and solvents (water, methanol, ethanol, acetone, dichloromethane, and hexane) on the antimicrobial and antioxidant activities of extracts from Olea europaea (olive) and Acacia dealbata (mimosa). Crude plant extracts were evaluated for their antimicrobial activity against Staphylococcus aureus and Escherichia coli by the disk diffusion method. The antioxidant capacity of the extracts was determined by ABTS (2,2-azinobis (3-ethyl-benzothiazoline-6-sulfonic acid)) and DPPH (2,2-diphenyl-1-picrylhydrazyl) methods. In terms of extraction yield, ultrasound extraction and the solvents methanol, acetone (O. europaea) or water (A. dealbata) were found to be the best options. However, ethanol and acetone proved to be the best solvents to extract compounds with antimicrobial activity and antioxidant capacity, respectively (regardless of the extraction method employed). Soxhlet and microwave were the best techniques to extract compounds with antimicrobial activity, whereas any of the tested techniques showed the ability to extract compounds with antioxidant capacity. In most of the cases, both plant extracts (mimosa and olive) were more efficient against S. aureus than E. coli. In the present study, both mimosa and olive leaf crude extracts proved to have antimicrobial and antioxidant activities, increasing the demand of these natural products as a source of compounds with health benefits.

AI snapshot

Written from the paper’s full text.

TL;DR

This study compared four extraction techniques and six solvents on antimicrobial and antioxidant activities of Olea europaea and Acacia dealbata leaf extracts. Ethanol was generally best for antimicrobial extraction, acetone for antioxidant extraction, and Soxhlet/microwave with water gave the highest extraction efficiencies and antimicrobial activity.

Key findings

  • Extraction efficiency: For O. europaea solid-liquid extraction ranged from 0.9% to 7.2% (hexane weakest, methanol best); for A. dealbata it ranged from 4.1% to 8.1% (dichloromethane weakest, water strongest, p < 0.05). Soxhlet and microwave with water gave 12.3% and 10.7% for olive, and 13.4% and 11.9% for mimosa.
  • Antimicrobial activity: For olive solid-liquid extracts, ethanol (25.3 mm) and acetone (22.7 mm) gave the largest inhibition halos against S. aureus; for olive ultrasound extracts, ethanol was best against both S. aureus (27.3 mm) and E. coli (16.7 mm). For mimosa solid-liquid extracts, ethanol gave the highest S. aureus inhibition (28.0 mm), while methanol gave the highest E. coli inhibition (16.7 mm). At standardized 5 mg/mL, activity decreased markedly; for olive solid-liquid extracts only ethanol remained active, with about 58% and 52% reductions against S. aureus and E. coli, respectively.
  • Soxhlet and microwave water extracts: Against S. aureus, halos were olive/Soxhlet 14.0 mm, olive/microwave 14.3 mm, mimosa/Soxhlet 14.7 mm, and mimosa/microwave 14.3 mm. Against E. coli, only olive extracts were active (Soxhlet 11.0 mm; microwave 11.7 mm); mimosa extracts showed no activity.
  • Antioxidant capacity: Acetone was the best solvent for both plants by DPPH and ABTS. For mimosa, acetonic extracts gave 782.9 TE/g fresh mass (solid-liquid) and 770.1 TE/g fresh mass (ultrasound) by DPPH; aqueous extracts gave 765.8 and 756.5 TE/g fresh mass, and methanolic extracts 739.8 and 730.8 TE/g fresh mass. By ABTS, acetone extracts gave 607.9 TE/g fresh mass for both solid-liquid and ultrasound mimosa extractions. No single extraction method excelled for antioxidant capacity; it depended largely on solvent.

Methods

  • Leaves of O. europaea and A. dealbata were collected in Braga, Portugal, in February 2013. Four extraction methods (solid-liquid, ultrasound, Soxhlet, microwave) and six solvents (water, methanol, ethanol, acetone, dichloromethane, hexane) were tested; Soxhlet and microwave used only water for safety reasons. Five grams of leaves were used per extraction.
  • Antimicrobial activity was assessed by disk diffusion against Staphylococcus aureus CECT 976 and Escherichia coli CECT 434, first at non-standardized extract concentrations and then at a standardized 5 mg/mL (0.05 mg/disc), with DMSO as negative control and inhibition zones recorded in mm.
  • Antioxidant capacity was measured by ABTS and DPPH radical scavenging assays, expressed as Trolox equivalents/g fresh mass. Experiments were performed in triplicate with at least three repeats; data were analyzed by one-way ANOVA with Tukey–Kramer test, significance at p < 0.05.

Limitations

  • The paper does not include a dedicated limitations section. It states that DPPH has limitations including restricted reactivity toward antioxidants and solubility in aqueous and organic solvents, and notes that different extraction conditions (e.g., higher time and/or temperature) might have changed results for aqueous extracts.
  • Evident from the text: antimicrobial testing used only two bacterial strains (S. aureus and E. coli), and initial antimicrobial assays used non-standardized extract concentrations, limiting direct comparability across solvents. Soxhlet and microwave were tested only with water, so technique and solvent effects are confounded for those methods.
  • Evident from the text: antioxidant activity was assessed only by chemical assays (ABTS, DPPH), with no cellular or in vivo validation, and the study did not quantify total phenolic or flavonoid contents of its own extracts.

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

Integrity signals

Registry

Crossref · 10.3390/antibiotics9020048

Cites

78 of 78 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 37 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    For Soxhlet and microwave extraction techniques using water as a solvent, the extraction efficiency was 13.4% and 11.9%, respectively.

    “For Soxhlet and microwave extraction techniques using water as a solvent, the extraction efficiency was 13.4% and 11.9%, respectively (Table 1).”
    Quote in the paperNot a substantial claim
  • Findingown data

    For mimosa solid-liquid extracts against S. aureus, highest antimicrobial activity was with ethanolic extracts (28.0 mm), followed by methanol (16.7 mm), acetone (12.0 mm), and hexane (11.3 mm) (p < 0.05).

    “For S. aureus, the highest antimicrobial activity was exhibited with ethanolic extracts (28.0 mm), followed by methanol (16.7 mm), acetone (12.0 mm), and hexane (11.3 mm) (p < 0.05)”
    Quote in the paperSubstantial claim
  • Findingown data

    Olive leaf solid-liquid extracts: significant antimicrobial activity was obtained with methanolic (16.7 mm) extracts followed by hexane (11.3 mm) and dichloromethane (8.7 mm) extracts.

    “Significant antimicrobial activity was also obtained with methanolic (16.7 mm) extracts followed by hexane (11.3 mm) and dichloromethane (8.7 mm) extracts.”
    Quote in the paperSubstantial claim
  • Findingown data

    At 5 mg/mL, for olive leaf ultrasound extracts against E. coli, only ethanol (10.7 mm) and acetone (10.7 mm) demonstrated inhibitory activity (p > 0.05).

    “For E. coli, only ethanol (10.7 mm) and acetone (10.7 mm) demonstrated inhibitory activity (p > 0.05).”
    Quote in the paperSubstantial claim
  • Findingown data

    For mimosa ultrasound extracts against E. coli, methanol, ethanol, and acetone demonstrated similar activity, with inhibition halos of 16.7 mm.

    “Methanol, ethanol, and acetone demonstrated similar activity against E. coli, with inhibition halos of 16.7 mm.”
    Quote in the paperNot a substantial claim
  • May combine two claims. 26
  • The quote only partly states this claim. 5
  • Classified as probably not a substantial claim. 14

  • May combine two claims.

    Findingown data

    Olive leaf solid-liquid extracts: ethanol (25.3 mm) and acetone (22.7 mm) caused the highest inhibition halo against S. aureus (p < 0.05), and differences between these two solvents were not significant (p > 0.05).

    “Extracts of ethanol (25.3 mm) and acetone (22.7 mm) caused the highest inhibition halo (p < 0.05) against S. aureus and the differences between these two solvents were not significant (p > 0.05).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Ethanol and acetone proved to be the best solvents to extract compounds with antimicrobial activity and antioxidant capacity, respectively, regardless of the extraction method employed.

    “However, ethanol and acetone proved to be the best solvents to extract compounds with antimicrobial activity and antioxidant capacity, respectively (regardless of the extraction method employed).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In terms of extraction yield, ultrasound extraction and the solvents methanol, acetone (O. europaea) or water (A. dealbata) were found to be the best options.

    “In terms of extraction yield, ultrasound extraction and the solvents methanol, acetone (O. europaea) or water (A. dealbata) were found to be the best options.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Olive leaf solid-liquid extracts: antimicrobial activity was found for almost all solvents, except water against both S. aureus and E. coli, and dichloromethane against E. coli.

    “Antimicrobial activity was found for almost all solvents, except water against both S. aureus and E. coli, and dichloromethane against E. coli (Table 2).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    No activity was found with mimosa ultrasound dichloromethane extract against both S. aureus and E. coli and with water extract against E. coli.

    “No activity was found with dichloromethane extract against both S. aureus and E. coli and with water extract against E. coli.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    For mimosa leaves, average extraction yield was 6.5% ± 1.7% for solid-liquid and 4.4% ± 1.4% for ultrasound extractions (p > 0.05).

    “For mimosa leaves, the values were 6.5% ± 1.7% and 4.4% ± 1.4% for solid-liquid and ultrasound extractions, respectively (p > 0.05).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    For ultrasound extraction, dichloromethane (2.8%) and acetone (7.4%) were the solvents that showed the lowest and highest efficacy, respectively (p < 0.05).

    “For ultrasound extraction, dichloromethane (2.8%) and acetone (7.4%) were the solvents that showed the lowest and highest efficacy, respectively (p < 0.05).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    In solid-liquid extraction of O. europaea, hexane was the weakest solvent and methanol the best one.

    “In this extraction method, hexane was the weakest solvent and methanol the best one.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    For A. dealbata, the solid-liquid extraction efficiency ranged from 4.1% to 8.1%, where dichloromethane was the weakest solvent and water was the strongest (p < 0.05).

    “Regarding A. dealbata, the efficiency ranged from 4.1% to 8.1%, where dichloromethane was the weakest solvent and water was the strongest (p < 0.05).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Concerning mimosa leaves extracts, water (6.4%) demonstrated higher extraction efficiency for the ultrasound method, whereas acetone (2.8%) showed lower efficiency.

    “Concerning the mimosa leaves extracts, water (6.4%) also demonstrated higher extraction efficiency for the ultrasound method, whereas acetone (2.8%) showed lower efficiency (Table 1).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    At 5 mg/mL, olive leaf solid-liquid ethanolic extracts showed a decrease in inhibition halo of about 58% against S. aureus (p < 0.05) and 52% against E. coli (p < 0.05).

    “Although, some activity was maintained for ethanolic extracts, a decrease in the inhibition halo of about 58% against S. aureus (p < 0.05) and 52% against E. coli (p < 0.05) was verified.”
    Quote in the paperSubstantial claim

  • The quote only partly states this claim.

    Findingown data

    Compared to higher concentrations, the inhibitory activity of olive leaf ultrasound extracts at 5 mg/mL decreased significantly (p < 0.05).

    “Compared to higher concentrations (no standardized concentrations), in general the inhibitory activity of the extracts decreased significantly (p < 0.05).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Soxhlet and microwave techniques using water as a solvent demonstrated good extraction efficiency at 12.3% and 10.7%, respectively.

    “Soxhlet and microwave techniques using water as a solvent demonstrated good extraction efficiency at 12.3% and 10.7%, respectively.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    For ultrasound extraction, the efficiencies for hexane, ethanol, methanol, and water were 3.2%, 4.6%, 6.0%, and 6.2%, respectively.

    “For the other solvents (hexane, ethanol, methanol, and water) the following efficiencies were obtained 3.2% < 4.6% < 6.0% < 6.2%, respectively.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    At 5 mg/mL, olive leaf ultrasound extracts: inhibition halos of 10.7 mm with ethanol, and 9.3 mm with both water and acetone against S. aureus.

    “Inhibition halos of 10.7 mm was obtained with ethanol, and of 9.3 mm were obtained with both water and acetone extracts.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    For olive leaves, average extraction yield with solid-liquid extraction was 5.1% ± 2.1% and for ultrasound extraction was 5.0% ± 1.8% (p > 0.05).

    “Bearing in mind all the solvents, for olive leaves, the average extraction yield with solid-liquid extraction was 5.1% ± 2.1% and for ultrasound extraction was 5.0% ± 1.8% (p > 0.05).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Both mimosa and olive leaf crude extracts proved to have antimicrobial and antioxidant activities.

    “In the present study, both mimosa and olive leaf crude extracts proved to have antimicrobial and antioxidant activities, increasing the demand of these natural products as a source of compounds with health benefits.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Dichloromethane (539.2 TE/g fresh mass) and ethanol (534.2 TE/g fresh mass) joined acetone as the best solvents in solid-liquid and ultrasound extractions, respectively (p < 0.05).

    “Moreover, dichloromethane (539.2 TE/g fresh mass) and ethanol (534.2 TE/g fresh mass) joined acetone as the best solvents in solid-liquid and ultrasound extractions, respectively (p < 0.05).”
    Quote in the paperSubstantial claim

  • The quote only partly states this claim.

    Findingown data

    For E. coli, no antimicrobial activity was observed with mimosa leaf extracts from Soxhlet and microwave extractions.

    “For E. coli, no antimicrobial activity was observed with mimosa leaf extracts.”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Findingown data

    At 5 mg/mL, for mimosa ultrasound extracts against E. coli, only ethanol (9.7 mm) demonstrated activity.

    “The same behavior was observed with ultrasound extraction for E. coli (ethanol—9.7 mm).”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Findingown data

    At 5 mg/mL, mimosa leaf extracts from Soxhlet and microwave did not show activity against E. coli.

    “At 5 mg/mL, the extracts obtained from mimosa leaves did not show activity against E. coli.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    For olive leaves with ultrasound extraction, the extract obtained with acetone demonstrated the best antioxidant capacity by ABTS, whereas by DPPH the aqueous extract was best (p < 0.05).

    “For ultrasound extraction, the extract obtained with acetone also demonstrated the best antioxidant capacity by ABTS, whereas by DPPH was the aqueous extract (p < 0.05).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    At 5 mg/mL, a decrease in concentration led the extracts to lose some activity, more evident against S. aureus (olive/Soxhlet 11.0 mm; olive/microwave 14.7 mm; mimosa/Soxhlet 10.3; mimosa/microwave 9.3 mm).

    “A decrease in the concentration to 5 mg/mL led the extracts losing some activity, which was more evident against S. aureus (olive/Soxhlet—11.0 mm; olive/microwave—14.7 mm; mimosa/Soxhlet—10.3; mimosa/microwave—9.3 mm).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    For S. aureus at higher concentrations, there were no significant differences in antibacterial activity between both plants and between Soxhlet and microwave extraction (olive/Soxhlet 14.0 mm; olive/microwave 14.3 mm; mimosa/Soxhlet 14.7; mimosa/microwave 14.3 mm) (p > 0.05).

    “For S. aureus, at higher concentrations, there were no significant differences in the antibacterial activity found with both plants and between the type of extraction (olive/Soxhlet—14.0 mm; olive/microwave—14.3 mm; mimosa/Soxhlet—14.7; mimosa/microwave—14.3 mm) (p > 0.05).”
    Quote in the paperNot a substantial claim

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

    Findingown data

    For Soxhlet and microwave extractions using water, concentrations of extracts ranged from 82.3 mg/mL to 123.5 mg/mL.

    “The extractions with Soxhlet and microwave used water as solvent and the concentrations of extracts obtained ranged from 82.3 mg/mL to 123.5 mg/mL (Table 2).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Extracts of O. europaea and A. dealbata leaves have antimicrobial and antioxidant activities.

    “This work allowed for the conclusion that extracts of O. europaea and A. dealbata leaves have antimicrobial and antioxidant activities.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The leaf samples collected from Braga in February 2013 are representative of O. europaea and A. dealbata species.

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

    Premisecitation

    The selection of the extraction solvent is the most important factor affecting the efficiency of solid-liquid extraction technique.

    “According to Altıok et al. [35], the selection of the extraction solvent is the most important factor affecting the efficiency of solid-liquid extraction technique.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [35] Bayraktar, 2008, Isolation of polyphenols from the extracts of olive leaves (Olea europaea L.) by adsorption on silk fibroin, Sep. Purif. Technol. source

      Not checked in the free run.

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

    Premisecitation

    Ultrasound extraction is a method highly efficient, requiring shorter extraction time when compared with other methods.

    “Shirzad and coworkers [40] studied the effect of different parameters (extraction time, temperature, ethanol-water ratio) in order to optimize ultrasound-assisted extraction of O. europaea leaves and concluded that ultrasound extraction is a method highly efficient, requiring shorter extraction time when compared with other methods.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [40] Shirzad, 2017, Ultrasound-assisted extraction process of phenolic antioxidants from Olive leaves: A nutraceutical study using RSM and LC–ESI–DAD–MS, J. Food Sci. Technol. source

      Not checked in the free run.

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

    Premisecitation

    In mixed form, individual components can modify their properties and interact synergistically, producing improved effects.

    “Additionally, in general, in the mixed form, individual components can modify their properties and interact synergistically, producing improved effects [18,25,39].”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [18] Lee, 2010, Antioxidant and antimicrobial activities of individual and combined phenolics in Olea europaea leaf extract, Bioresour. Technol. source

      Not checked in the free run.

    • cites [25] Pereira, 2007, Phenolic compounds and antimicrobial activity of olive (Olea europaea L. Cv. Cobrançosa) leaves, Molecules source

      Not checked in the free run.

    • cites [39] Mehmood, A., and Murtaza, G. (2018). Phenolic contents, antimicrobial and antioxidant activity of Olea ferruginea Royle (Oleaceae). BMC Complement. Altern. Med., 18. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Olive leaves contain an array of simple phenolics (phenylethanoids, hydroxybenzoic acids, and hydroxycinnamic acids) and polyphenolic compounds (secoiridoids and flavonoids) with biological properties, including antioxidant and antimicrobial.

    “Among all by-products, olives leaves have attracted growing attention as they contain an array of simple phenolics (phenylethanoids, hydroxybenzoic acids, and hydroxycinnamic acids) and polyphenolic compounds (secoiridoids and flavonoids) with biological properties, including antioxidant and antimicrobial [16,17,18,19,20,21,22,23].”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [16] Brahmi, 2012, The efficacy of phenolics compounds with different polarities as antioxidants from olive leaves depending on seasonal variations, Ind. Crops Prod. source

      Not checked in the free run.

    • cites [17] Castillo, 2000, Antioxidant activity of phenolics extracted from Olea europaea L. leaves, Food Chem. source

      Not checked in the free run.

    • cites [18] Lee, 2010, Antioxidant and antimicrobial activities of individual and combined phenolics in Olea europaea leaf extract, Bioresour. Technol. source

      Not checked in the free run.

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

    Premisecitation

    Microwave is an advantageous process of extraction, as it is simple, fast, and requires a small amount of solvent.

    “It has been described that microwave is an advantageous process of extraction, as it is simple, fast, and requires a small amount of solvent. Moreover, this technique facilitates the extraction of compounds with bioactivity due to the rapid heating of the matrix [21].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [21] Grumezescu, A.M., and Holban, A.M. (2017). Chapter 11—Extraction of bioactive compounds from olive leaves using emerging technologies. Ingredients Extraction by Physicochemical Methods in Food, Academic Press. source

      Not checked in the free run.

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

    Premisecitation

    A methanol/water mixture was the best solvent to attain olive leaf extracts rich in flavonoids and with considerable antioxidant properties (Abaza et al.).

    “These authors also verified that a methanol/water mixture was the best solvent to attain extracts rich in flavonoids and with considerable antioxidant properties.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [68] Abaza, 2011, Chétoui olive leaf extracts: Influence of the solvent type on phenolics and antioxidant activities, Grasas Aceites source

      Not checked in the free run.

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

    Premisecitation

    Phenolic compounds have antioxidant activity mainly due to their redox properties, allowing them to act as reducing agents, hydrogen donors, and singlet oxygen quenchers.

    “Phenolic compounds have antioxidant activity mainly due to their redox properties, which allows them to act as reducing agents, hydrogen donors, and singlet oxygen quenchers [49,54].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [49] Gallo, 2010, Microwave assisted extraction of phenolic compounds from four different spices, Molecules source

      Not checked in the free run.

    • cites [54] Debib, 2017, Phenolic content, antioxidant and antimicrobial activities of “Chemlali” olive leaf (Olea europaea L.) extracts, Int. J. Pharmacol. Phytochem. Ethnomed.

      Not checked in the free run.

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

    Premisecitation

    Methanol and water are the solvents that can extract more diversity of compounds.

    “According to Cowan [46], methanol and water are the solvents that can extract more diversity of compounds, which can explain the higher extraction efficiency.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [46] Cowan, 1999, Plant products as antimicrobial agents, Clin. Microbiol. Rev. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Some characteristics of acetone such as volatility, miscibility with polar and non-polar solvents, and moderately low toxicity to some microorganisms (e.g., S. aureus and Pseudomonas aeruginosa), makes it a very useful extraction solvent.

    “Moreover, some characteristics of acetone such as volatility, miscibility with polar and non-polar solvents, and moderately low toxicity to some microorganisms (e.g., S. aureus and Pseudomonas aeruginosa), makes it a very useful extraction solvent [70].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [70] Eloff, 1998, Which extractant should be used for the screening and isolation of antimicrobial components from plants?, J. Ethnopharmacol. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Acetone is very effective in extracting antioxidants such as phenolics, being one of the main solvents used to extract this class of compounds from plants.

    “In fact, acetone is very effective in extracting antioxidants such as phenolics, being one of the main solvents used to extract this class of compounds from plants [69].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [69] Anokwuru, 2011, Effect of extraction solvents on phenolic, flavonoid and antioxidant activities of three Nigerian medicinal plants, Nat. Sci.

      Not checked in the free run.

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

    Premisecitation

    Some studies have already reported the antioxidant capacity of olive and mimosa leaf extracts.

    “Some studies have already reported the antioxidant capacity of olive [17,18,22] and mimosa leaf [8,71] extracts.”
    Quote in the paperNot a substantial claim0 of 5 sources checked
    • cites [17] Castillo, 2000, Antioxidant activity of phenolics extracted from Olea europaea L. leaves, Food Chem. source

      Not checked in the free run.

    • cites [18] Lee, 2010, Antioxidant and antimicrobial activities of individual and combined phenolics in Olea europaea leaf extract, Bioresour. Technol. source

      Not checked in the free run.

    • cites [22] Lins, 2018, In vitro antioxidant activity of olive leaf extract (Olea europaea L.) and its protective effect on oxidative damage in human erythrocytes, Heliyon source

      Not checked in the free run.

    • cites [8] Luis, 2012, Antioxidant activities of extracts from Acacia melanoxylon, Acacia dealbata and Olea europaea and alkaloids estimation, Int. J. Pharm. Pharm. Sci.

      Not checked in the free run.

    • cites [71] Tung, 2009, Free radical-scavenging phytochemicals of hot water extracts of Acacia confusa leaves detected by an on-line screening method, Food Chem. source

      Not checked in the free run.

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

    Premisecitation

    The presence of an outer membrane in Gram-negative bacteria acts as a powerful barrier, restricting the diffusion of compounds through its lipopolysaccharide layer.

    “The presence of an outer membrane in Gram-negative bacteria acts as a powerful barrier, restricting the diffusion of compounds through its lipopolysaccharide layer [56].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [56] Vaara, 1992, Agents that increase the permeability of the outer membrane, Microbiol. Rev. source

      Not checked in the free run.

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

    Premisecitation

    Martysiak-Żurowska et al. concluded that DPPH demonstrated lower sensitivity than ABTS for assessing total antioxidant capacity of human milk.

    “Martysiak-Żurowska et al. [64] carried out a comparative study on the assessment of the total antioxidant capacity of human milk by the ABTS and DPPH methods, and concluded that the latter demonstrated lower sensitivity.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [64] Wenta, 2012, A comparison of ABTS and DPPH methods for assessing the total antioxidant capacity of human milk, Acta Sci. Pol. Technol. Aliment.

      Not checked in the free run.

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

    Premisecitation

    The results of Debib et al. indicated that phenolic compounds appeared to be mainly responsible for the effects observed.

    “The results indicated that the phenolic compounds appeared to be mainly responsible for the effects observed.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [54] Debib, 2017, Phenolic content, antioxidant and antimicrobial activities of “Chemlali” olive leaf (Olea europaea L.) extracts, Int. J. Pharmacol. Phytochem. Ethnomed.

      Not checked in the free run.

  • The quote only partly states this claim.

    Interpretationown data

    Olive and mimosa leaf extracts have identical ability to scavenge free radicals.

    “This proposes that olive and mimosa leaf extracts the have identical ability to scavenge free radicals.”
    Quote in the paperSubstantial claim

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

    Premisecitation

    Limitations of the DPPH method include restricted reactivity towards antioxidants and solubility in aqueous and organic solvents.

    “These observations were probably due to limitations of the DPPH method that include restricted reactivity towards antioxidants and solubility in aqueous and organic solvents [74].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [74] Cano, 2000, A method to measure antioxidant activity in organic media: Application to lipophilic vitamins, Redox Rep. source

      Not checked in the free run.

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

    Study design and conductnone given

    The experiments were performed in triplicate with a minimum of three repeats.

    “The experiments were performed in triplicate with a minimum of three repeats.”
    Quote in the paperNot a substantial claim
43 of 43

  • The paper relies on this without support.

    Optimization of plant molecule extraction is fundamental in obtaining relevant extraction yields.

    “The optimization of plant molecule extraction is fundamental in obtaining relevant extraction yields.”

  • The paper relies on this without support.

    Health hazards are frequently associated with the use of chemical antimicrobial agents or food preservatives.

    “This is of valuable importance, as health hazards are frequently associated with the use of chemical antimicrobial agents or food preservatives.”

  • The paper relies on this without support.

    The leaf samples collected from Braga in February 2013 are representative of O. europaea and A. dealbata species.

    “The plants selected for this study were O. europaea and A. dealbata, collected from the area of Braga (Braga, Portugal). Fresh leaves were collected in February 2013 and immediately processed.”
3 of 3

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?

  • Studies have shown that aqueous alcoholic extraction solvents, such as ethanol-water mixtures, can be highly effective in extracting a range of bioactive compounds, including flavonoids.

    “Additionally, studies have shown that aqueous alcoholic extraction solvents, such as ethanol–water mixtures, can be highly effective in extracting a range of bioactive compounds, including flavonoids [53,54,55].”

    From Comparative Analysis of Infusions and Ethanolic Extracts of Annona muricata Leaves from Colima, Mexico: Phytochemical Profile and Antioxidant Activity (2024) · cites this paper as [54]

    Section 2.1 reports that water–ethanol mixtures were generally more effective than either solvent alone at extracting polyphenolic compounds from olive leaves. Section 2.3 discusses flavonoids in methanolic olive-leaf extracts, but does not establish that ethanol–water mixtures effectively extract flavonoids specifically; this paper tested the solvents separately. (LLM, conf=0.83)

    Experimental — accuracy not yet measured

  • Despite not being the optimum extraction solvent, water could effectively extract polyphenols across plant tissues.

    “Despite not being the optimum extraction solvent, water could effectively extract polyphenols across plant tissues [44].”

    From Bioactive Compound Extraction of Hemp ( Cannabis sativa L.) Leaves through Response Surface Methodology Optimization (2024) · cites this paper as [44]

    Section 2.3 reports that olive-leaf extracts made with water contained phenolic compounds, while Section 2.1 says water helps extractable compounds diffuse through plant tissues. However, the paper does not establish effective polyphenol extraction across plant tissues generally; its own solvent comparisons concern olive and mimosa leaves, and water was the highest-yielding solvent under some conditions. (LLM, conf=0.82)

    Experimental — accuracy not yet measured

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.

  • Abstract calls ultrasound the best method for extraction yield

    Minor

    The abstract identifies ultrasound extraction as a best option for yield, but the results state that Soxhlet and microwave provided the more efficient extraction for both plants.

  • Olive microwave inhibition halo increases at the lower concentration

    Minor

    The text says reducing the extract concentration to 5 mg/mL caused a loss of activity, but the reported olive microwave inhibition halo against S. aureus rises from 14.3 mm at the higher concentration to 14.7 mm at 5 mg/mL.

2 of 2

Cites

Flagged first, then by citations

9 of the 87 references couldn’t be matched to a known paper.

Research works printed but not linked: 4

  1. Luis, 2012, Antioxidant activities of extracts from Acacia melanoxylon, Acacia dealbata and Olea europaea and alkaloids estimation, Int. J. Pharm. Pharm. Sci., 4, 225
  2. Zaynab, 2015, Antioxidant activity of Olea europaea L. extracts from two different regions of Iran, Int. J. Agric. Crop Sci., 8, 68
  3. Keskin, 2012, Antimicrobial activity and chemical constitutions of West Anatolian olive (Olea europaea L.) leaves, J. Food Agric. Environ., 10, 99
  4. Anokwuru, 2011, Effect of extraction solvents on phenolic, flavonoid and antioxidant activities of three Nigerian medicinal plants, Nat. Sci., 9, 53

Cited by

Sorted by citations

Related

Authors
Borges, A., José, H., Homem, V., & Simões, M.
Affiliations
Universidade do Porto (PT)
Corresponding author
Simões, Manuel
ORCID
Venue
Antibiotics
Publisher
MDPI AG
Published
2020-01-28
Volume
9
Issue
2
Pages
48
ISSN
2079-6382 (ISSN-L)
DOI
10.3390/antibiotics9020048
PMC
PMC7168226
OpenAlex
W3004378703
Semantic Scholar
9031ff8fdeeb6265b96d7f4302121c5baf486d45
Cited by
184
References
87
Citations by year
2026: 21 · 2025: 47 · 2024: 47 · 2023: 33 · 2022: 21 · 2021: 11 · 2020: 3
FWCI
11.03
Type
journal article
Language
en
Open access
Licence
Locations
  • Antibiotics (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • Portuguese National Funding Agency for Science, Research and Technology (RCAAP Project by FCT) (submittedVersion, other-oa)
Topics
  • Life Sciences › Agricultural and Biological Sciences › Food Science › Essential Oils and Antimicrobial Activity
  • Life Sciences › Agricultural and Biological Sciences › Plant Science › Medicinal Plant Research
  • Life Sciences › Agricultural and Biological Sciences › Food Science › Agricultural and Biological Research
Keywords
Acacia dealbata, Olea europaea, herbal extract preparation, extraction solvents, ultrasound-assisted extraction, microwave-assisted extraction, Soxhlet extraction, antimicrobial activity, antioxidant capacity, Staphylococcus aureus, Escherichia coli, olive leaf extract, extraction yield

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.

What counts as a claim ›How we measure confidence ›How we check this ›

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