Bioactive Compounds of Cold-pressed Thyme (Thymus vulgaris) Oil with Antioxidant and Antimicrobial Properties

Abstract

Herbs rich in bioactive phytochemicals were recognized to have biological activities and possess many health-promoting effects. In this work, cold-pressed thyme (Thymus vulgaris L.) oil (TO) was studied for its lipid classes, fatty acid profile, tocols and phenolics contents. Antioxidant activity and radical scavenging potential of TO against free radicals (DPPH^・ and galvinoxyl) was determined. Antimicrobial activity (AA) of TO against food borne bacteria, food spoilage fungi and dermatophyte fungi were also evaluated. Neutral lipids accounted for the main lipid fraction in TO, followed by glycolipids and phospholipids. The major fatty acids in TO were linoleic, oleic, stearic, and palmitic. γ-Tocopherol (60.2% of total tocols) followed by α-tocotrienol (26.9%) and α-tocopherol (9.01% of total tocols) were the main tocols. TO contained high amounts of phenolic compounds (7.3 mg/g as GAE). TO had strong antiradical action wherein 65% of DPPH^・ radicals and 55% of galvinoxyl radical were quenched after 60 min of incubation. Rancimat assay showed that induction time (IT) for TO: sunflower oil blend (1:9, w/w) was 6.5 h, while TO: sunflower oil blend (2:8, w/w) recorded higher IT (9 h). TO inhibited the growth of all tested microorganisms. TO exhibited various degrees of AA against different food borne bacteria, food spoilage fungi and dermatophyte fungi, wherein the highest AA was recorded against dermatophyte fungi and yeasts including T. mentagrophytes (62 mm), T. rubrum (40 mm), and C. albicans (20 mm) followed by food spoilage fungi including A. flavus (32 mm) with minimal lethal concentrations (MLC) ranging between 80 to 320 μg/mL. Furthermore, TO exhibited broad-spectra activity against food borne bacteria including S. aureus (30 mm), E. coli (25 mm) and L. Monocytogenes (20 mm) with MLC ranging between 160 to 320 μg/mL. The results suggest that TO could be used economically as a valuable natural product with novel functional properties in food, cosmetics and pharmaceutical industries.