The Effect of Non-thermal Processing of Hyssopus officinalis on its Antioxidant and Antimicrobial Activities

Hyssopus of­ficinalis L. is one of the most important medicinal plants. Medicinal herbs are contaminated by microorganisms. Conventional methods for reducing of microbial loads such as ethylene oxide, propylene oxide and also use of steam are hazardous and instead, non-thermal process such as microwave and gamma radiation are being used widely in order to eliminate the microbial contaminations with no or a little side effect. In the present study the effect of gamma and microwave irradiation on antioxidant and antimicrobial activities of Hyssopus of­ficinalis L. was investigated. Hyssopus samples were exposed to gamma  irradiation at doses 10, 15, 20 and 25 kGy and microwave irradiationat power of 300, 450 and 600 W for 5 min. In order to undergo the sequence experiments, the hydroalcoholic (EtOH 50%) extracts of plant were prepared. The antioxidant activities of irradiated and control samples were evaluated by DPPH radical scavenging (RS), ferric reducing power (FRP), β-carotene bleaching (BCB) and total phenolic content (TPC) of sampels. In order to study the antimicrobial activity, for determination of minimal inhibitory concentration (MIC) on E. coli and S. aureus,broth diluting method was used. Results showed that gamma irradiation had no significant effect on antioxidant parameters, phenolic content and antimicrobial activities of sampels. Microwave treatment of Hyssopus at 300, 450 and 600 W for 5 min increased its antioxidant and antimicrobial activities. Results indicated that gamma and microwave irradiation do not have any negative effect on antioxidant and antimicrobial activities of Hyssopus.