COMPARATIVE STUDY ON THE EFFECT OF DIFFERENT METHODS OF DRYING ON PHENOLICS CONTENT AND ANTIOXIDANT ACTIVITY OF SOME EDIBLE PLANTS

Antioxidants have important role in prevention and treatment of disorders and plants are considered as rich sources of radical scavenging compounds. Nowadays, many herbs are used in dried form which is possible to affect their antioxidant activity. In the present investigation, the effects of different drying methods on the antioxidant capacity and total phenolics content of some culinary plant species have been studied. Leaves of Mentha piperita, Mentha spicata, Thymus vulgaris and Anethum graveolense were dried in sun, shade, oven and microwave and extracted with methanol. Antioxidant activity of each extract was determined by DPPH free radicals and total phenolics content was measured by folin cio-calteus reagent. The results revealed that drying process reduced the antioxidant activity of  Anethum graveolense whereas sun-drying and shade-drying increased the antioxidant activity of Mentha piperita, Mentha spicata and Thymus vulgaris (Lamiaceae). During sun-drying and shade-drying, total phenolics content increased for the three plants of Lamiaceae while oven- and microwave-drying reduced the phenolics content. Drying also declined the phenolics content of Anethum graveolense which gives the conclusion that some kind of correlation could be established between total phenolics content and antioxidant behavior for the three Lamiaceae and Anethum graveolense. Our study brought the view that diversity in the methods of drying could lead to different phenolics content and antioxidant behavior, suggesting that each plant needs a special drying method.