Effect of gamma ray irradiation on chemical composition, antioxidant, antimicrobial, and insecticidal activities of Thymus pallescens essential oil

[摘要] The essential oils isolated by hydrodistillation from Thymus pallescens de Noé dried leaves exposed to γ-irradiation at dose levels of 0, 5, 10, 20, and 30 kGy were analyzed by gas chromatography–flame ionization detector (GC–FID) and GC–mass spectrometry (MS) and tested for their antioxidant, antimicrobial, and insecticidal activities. No qualitative change was observed in the chemical composition. Carvacrol (81.8–85.7%) was the most prominent component. Gamma-irradiation at 20 kGy affects quantitatively some components. Antioxidant activity was evaluated by four different test systems, namely, inhibition of lipid peroxidation (thiobarbituric acid reactive substance, TBARS), ferric reducing power, and scavenging of radicals DPPH• and ABTS•+. In all systems, irradiated oils at 20 and/or 30 kGy showed the most antioxidant efficiency. Overall, the antimicrobial activity conducted against seven microorganisms revealed no significant changes according to the radiation dose. Fumigation bioassays and contact method against confused flour beetle Tribolium confusum revealed that the oil irradiated at 20 kGy had highest insecticidal activity. The results showed that gamma-irradiation of T. pallescens could be not only beneficial safe decontamination perspective but also as an improvement factor of some of its properties.

[学科分类] 化学（综合）

[关键词] T. pallescens;irradiation;essential oil;GC–MS;antioxidant activity;antimicrobial activity;insecticidal activity