Essential oils of Thymus munbyanus subsp. coloratus: chemical variability and evaluation of biological activities

Abstract

The chemical compositions of Thymus munbyanus subsp. coloratus essential oils, an endemic plant in north Africa, were investigated using gas chromatography with flame ionization detection and gas chromatography-mass spectrometry. The antioxidant activity of the studied essential oils was evaluated through 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,20-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) free-radical scavenging assays. Disc diffusion method and minimal inhibitory concentration (MIC) determination were applied to investigate the antimicrobial activity of Thymus munbyanus subsp. coloratus essential oil against ten bacterial and fungus strains. Fifty-one compounds were identified accounting for 90.3-95.9% of the total amount. Camphor (04.09-25.92%) was the major component in the essential oils obtained from five localities, followed by myrcene (00.66-17.11%) in four stations, then borneol (07.37-38.96%) in the essential oil obtained from three samples. The chemical variability of Thymus munbyanus subsp. coloratus essential oils was studied using statistical analysis, in which we found a direct relationship between geo climatic conditions and their chemical compositions. Thymus munbyanus subsp. coloratus essential oils exhibited a good radical-scavenging activity with IC50 values up to 0.250 ± 0.51 and 0.596 ± 0.15 (mg/mL) in reductive potential of ABTS and DPPH free radicals, respectively, and a significant antimicrobial activity against Gram positive bacteria and fungal species with MIC up to 0.66 ± 0.28 (mg/mL) against Aspergillus flavus.