Synergism between eugenol and antibiotics.
Article Type: Report
Subject: Antibiotics (Dosage and administration)
Eugenol (Usage)
Eugenol (Health aspects)
Gram-negative bacterial infections (Care and treatment)
Gram-negative bacterial infections (Research)
Author: Finney-Brown, Tessa
Pub Date: 12/22/2009
Publication: Name: Australian Journal of Medical Herbalism Publisher: National Herbalists Association of Australia Audience: Academic Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2009 National Herbalists Association of Australia ISSN: 1033-8330
Issue: Date: Winter, 2009 Source Volume: 21 Source Issue: 4
Topic: Event Code: 310 Science & research
Product: SIC Code: 2834 Pharmaceutical preparations
Geographic: Geographic Scope: Australia Geographic Code: 8AUST Australia
Accession Number: 215249525
Full Text: Hemaiswarya S, Doble M. 2009. Synergistic interaction of eugenol with antibiotics against gram negative bacteria. Phytomed 16:11;997-1005.

The terpene euganol is the main constituent of clove oil from Eugenia aromatica and is present in a number of other essential oils of medicinal plants such as Cinnamomum species. It has known antibacterial effects especially against pathogens including Escherichia coli O157:H7, Listeria monocytogenes, Campylobacter jejuni, Salmonella enterica, Staphylococcus aureus, Lactobacillus sakei and Helicobacter pyroli. It seems to exert its effects primarily by disrupting the cellular cytoplasmic membrane.

The current study was designed to evaluate the synergistic effect between euganol and ten hydrophobic and hydrophilic antibiotics against five gram negative bacteria. The strains chosen were Escherichia coli (NCIM 2931), Enterobacter aerogenes (NCIM 5139), Proteus vulgaris (NCIM 2813), Salmonella typhimurium (NCIM 2501), and Pseudomonas aeruginosa (NCIM 5029). The antibiotics used were penicillin, ampicillin, oxacillin, erythromycin, polymyxin B sulphate, tetracycline, chloramphenicol, vancomycin, rifampin and norfloxacin. All of the antibiotics tested were active against the gram negative bacteria except for penicillin, oxacillin, vancomycin and erythromycin. The euganol alone was considered to be active against the bacteria, with cell membrane damage of 50% at a concentration of 1 mM and 80% at 10 mM. It was more active against hydrophic bacteria such as P. vulgaris.

When euganol was combined with the antibiotics in question there was nearly a 5-1000 fold decrease in minimum inhibitory concentration (MIC--the lowest quantity of an antibiotic that will inhibit the visible growth of a microorganism after overnight culture) of the drugs tested. Additionally those antibiotics that were non specific against gram negative bacteria became more effective in the presence of euganol. It may assist the activity of the drugs by increasing the non specific permeability of the cell or by acting on different targets on the cytoplasmic membrane, thus enhancing the damage done to the bacteria. Secondary activities at sublethal concentrations may also be possible.

Although this was an in vitro study the authors discuss previous murine models utilising euganol and extrapolate that an oral dose of 0.3 g/kg body weight is needed to achieve the necessary synergy with the antibiotics. They point out that the pharmacokinetic and pharmacodynamic values for the drugs and euganol may be different when used in combination and did not consider it prudent to extrapolate the individual drug data to combination therapy.

Tessa Finney-Brown MNHAA
Gale Copyright: Copyright 2009 Gale, Cengage Learning. All rights reserved.

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