Antioxidant activity of polyphenols from Lycopus lucidus Turcz

The aim of this paper was to evaluate the antioxidant properties of the different extracts from Lycopus lucidus (crude methanolic extract, dichloromethane, diethyl ether and ethyl acetate sub-fractions) and to correlate their antioxidant potential to the composition of polyphenols. The ability of deactivating free radicals was measured using DPPH and NO scavenging assays. The reducing power towards transition metals was tested by the phosphomolybdenum method. Qualitative and quantitative analyses of major phenolic acids were also performed. The main antioxidant compound from the methanol extract was confirmed to be rosmarinic acid. Other identified phenolic acids that are likely to contribute to the antioxidant potential are: ferulic, caffeic, chlorogenic, vanillic, p-hydroxybenzoic acid, p-coumaric acid and protocatechuic acid. The most active ethyl acetate extract contained the highest level of rosmarinic acid, but the luteolin glycosides are also the major determinants of the antioxidant activity as has been revealed by analysis of the two most active fractions from column chromatography. These two classes of antioxidants are likely to act synergistically in the ethyl acetate fraction and the crude extract of the plant.