Composition and radical-scavenging activity of Thymus glabrescens Willd. (Lamiaceae) essential oil

Abstract

BACKGROUND: Knowledge about the chemical and therapeutic properties of Thymus glabrescens Willd. (Lamiaceae) is scarce and inconsistent. Therefore the main objectives of this study were to determine the yield and chemical composition of essential oils from wild-growing T. glabrescens populations, to assess their radical scavenging activity and to correlate the results with published data in order to deduce which components are responsible for the activity. RESULTS: The plant material yielded between 4.0 and 8.0 mL kg(-1) of essential oil. All samples contained considerable but variable concentrations of thymol (22.3-55.1%), depending on the source. Radical-scavenging activities of the oils were estimated by 1,1-diphenyl-2-picrylhydrazyl free radical (DPPH) assay against butylated hydroxytoluene (BHT) and thymol as positive controls. The observed activities (IC50 values ranged from 94 to 230 mu gmL(-1)) were strongly influenced by thymol concentration, as verified by rapid screening for DPPH radical-scavenging activity on thin layer chromatography (TLC) plates and regression analysis. CONCLUSION: These results represent the first report on the free radical-scavenging activity of T. glabrescens essential oil and one of the first comprehensive reports on its composition. Thymus glabrescens could be used in the food industry for seasoning purposes or for preserving processed foods from oxidative degradation.