Effect of Gamma Irradiation on the Chemical Composition and Antioxidant Activity of Thymus algeriensis Extracts

Thymus algeriensis Boiss. et Reut. pretreated with gamma irradiation at the doses of 0, 10, 20 and 30 kGy were submitted to hydrodistillation and the resulted essential oils were analyzed for their chemical composition by GC and GC-MS and for their antioxidant activity evaluated by inhibition of lipid peroxidation, ferric reducing antioxidant power and scavenging of radicals DPPH center dot and ABTS(center dot+). On the other hand, the non volatile ethanol extracts obtained by Soxhlet, were analyzed in terms of the dosage of total phenols and flavonoids and for their antioxidant activity. Although there were no qualitative changes in the chemical composition of the essential oils of the irradiated samples, minor quantitative changes were observed for some compounds for some irradiation doses, especially for the three main components: carvacrol for all the doses in addition to p-cymene and gamma-terpinene for 10 kGy and gamma-terpinene for 30 kGy. The antioxidant activity of the oils was dependent on the method employed to determine such activity. Total phenolics content (149.33-236.17 mg GAE/g Extract) and flavonoids (35.74 - 52.25 mg QE/g Extract) as well as the antioxidant activities decrease for the samples irradiated at 20 and 30 kGy. Contrariwise, the irradiation at 10 kGy increases total phenolic content and antioxidant activity. The results suggest that gamma-irradiation of T algeriensis up to 10 kGy could be used as beneficial decontamination process.