Abstract

This work investigates the phenolic, antioxidant capacity of crude extracts of eight Egyptian medicinal plants (Syrian oregano, marjoram, rosemary, lemongrass, thyme, yarrow, marigold and sweet wormwood) and estimates their activity against Listeria monocytogenes, one of the most virulent food borne pathogens. Antioxidant activity of Rosemary (70.6±1.65%) and thyme (70.8±1.72%) based on TBA assay was significantly higher compared to other plants and ascorbic acid. Rosemary was found to possess the best antilisterial activity with lowest MBC (8 µl/ml); while its total phenolic content (TPC) represented 69.73 ± 0.47 mg/g GAE. Thyme showed MBC of 46 µl/ml with TPC 96.85±0.56 mg/g GAE. Lemon grass and marigold showed considerable antilisterial activity (MBC 31, 46 µl/ml respectively), although they had lower phenolic contents and low thiobarbituric acid inhibition. Sweet wormwood, marjoram and yarrow were inactive against listeria. Rosemary and thyme appeared as possible alternatives for synthetic food additives and preservatives.

Key words: Medicinal plants, anti-listerial, antioxidant, rosemary, thyme.