Chemical composition and antibacterial activity of Thymus zygis subsp. gracilis (Boiss.) R. Morales essential oils from Morocco

Abstract

Thymus zygis subsp. gracilis samples were collected from different Moroccan Middle Atlas sites at three phenological stages. Chemical composition of essential oils obtained from these samples was studied and their antimicrobial activity was evaluated. GC-MS analysis of essential oils shows quantitative and qualitative changes in the chemical profile. Twenty-three components were detected. These compounds fall under at least four chemical families whose relative importance varies with the sites and the phenological stages. Monoterpens were the most abundant and their percentage in essential oils varied from 61.38 to 94.91. Carvacrol (16.07 to 74.33%), thymol (1.47 to 32.46%), p-cymene (6.97 to 40.26%) and γ-terpinene (2.68 to 22%) were the main constituents. Bactericidal property of Thymus zygis essential oils was also evaluated in vitro against six strains of phytopathogenic bacteria. All bacterial strains tested were susceptible to essential oils. Maximum activity was observed against the Gram-negative bacterium Erwinia amylovora and Gram-positive actinomycete Streptomyces scabiei. The most bactericidal effect was observed against Streptomyces scabei. Its minimum bactericidal concentration (MBC) was 50 μg.mL-1 . At post-flowering stage, carvacrol chemical profile was the most efficient.