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

The DOI matches its Crossref record; 78 of the 87 references it cites were found in a registry or an index; 2 of the 37 sources its claims cite were checked for support.

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

Open access

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.

Overview

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.

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Integrity signals

Registry

Crossref · 10.3390/antibiotics9020048

Cites

78 of 78 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

79 Own result · 21 Not checked yet · 9 No basis given · 5 Own interpretation · 1 Partly supported · 1 Own method · accuracy not yet measured

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Show all 73 claims

  • Probably not a substantial claim. 14
  • It may state two separate claims as one. 26
  • The quote only partly states this claim. 5
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

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2 of 2

Citations

Cites

Show all 87 references

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

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Metadata

Authors
Borges, A., José, H., Homem, V., & Simões, M.
Affiliations
Universidade do Porto (PT)
Corresponding author
Simões, Manuel
Venue
Antibiotics
Publisher
MDPI AG
Published
2020-01-28
Volume
9
Issue
2
Pages
48
ISSN
2079-6382 (ISSN-L)
OpenAlex
W3004378703
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
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

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