Antioxidant activity and components of Salvia plebeia R.Br. — a Chinese herb

The antioxidant properties of the extracts from Salvia plebeia R.Br. which was screened out of over 700 species of Chinese herbs, were tested in lard at 110°C using the Oxidative Stability Instrument. The ethyl acetate extract of the herb was re-extracted by solvents (with increasing polarity) into petroleum ether-, diethyl ether-, acetone-and-ethanol-soluble fractions. The fractions obtained were then separated according to their acidic properties. From the most active sub-fractions, namely the acidic sub-fraction of the petroleum ether-soluble fraction and the weakly acidic sub-fraction of the diethyl ether-soluble fraction, three antioxidant components were isolated and identified as royleanonic acid, hispidulin and eupatorin. The royleanonic acid was a novel compound and eupatorin was isolated for the first time from the herb. Though royleanonic acid and hispidulin prolonged the induction period significantly, their antioxidant activities were much weaker than the crude extracts, implying that synergistic effects might be responsible for the high activity of the crude extracts.