ANTIOXIDANT ACTIVITY OF PLANT-LEAVES IN RELATION TO THEIR ALPHA-TOCOPHEROL CONTENT

The leaf alpha-tocopherol content of fifteen plant species was determined by a gas-chromatographic method with alpha-tocopherol acetate used as internal standard. Highest amounts were found in leaves of Pelargonium sp. (412 ppm) and Thalictrum flavum (371 ppm), which could represent an interesting source of alpha-tocopherol for different purposes, such as the stabilization of food products. Antioxidant activity of leaf extracts was evaluated spectrophotometrically by coupled oxidation of beta-carotene and linoleic acid. The species could thus be ranked on the basis of an antioxidant-activity coefficient. Correlation established between the alpha-tocopherol content and antioxidant activity yielded a coefficient of 0.93, suggesting that alpha-tocopherol is the major liposoluble antioxidant found in leaves.