A COMPARISON OF THE ANTIOXIDANT ACTIVITY AND PHENOLIC CONTENT OF NONPOLAR AND POLAR EXTRACTS OBTAINED FROM FOUR ENDEMIC LAMIACEAE SPECIES GROWN IN GREECE

This study was designed to compare the phenolic content and antioxidant properties of non-polar and polar fractions of Origanum onites, O. dictamnus, Thymus vulgaris and Rosmarinus officinalis that are grown in the same region (Crete, Greece). In the beta-carotene/linoleic acid system the hexane extracts showed higher antioxidant activity (P < 0.05) than methanol and dichoromethane extracts did (mean value: 73.53, 52.79 and 33.5%, respectively). Oregano exhibited stronger antioxidant activity (P < 0.05) than rosemary, thyme and dittany. The dichloromethane and methanol extracts appeared to have a higher radical scavenging activity (P < 0.05) than the hexane extracts (mean 50% inhibition value: 1.62, 1.21 and 7.71, respectively). The dichloromethane extracts showed strong inhibition in the corn oil oxidation (up to 81.1%), which is higher when compared with that of butylated hydroxytoluene (42.07%). Rosemary was a stronger inhibitor in the oil oxidation (P < 0.05) than oregano, thyme and dittany. High and positive correlations were observed between the total flavonoids of the methanol plant extracts and their antioxidant activity in all the three assays.