Antioxidant activity of compounds isolated from Salvia plebeia

Six compounds, hispidulin-glucuronide (1), hispidulin-7-O-d-glucoside (2), 6-methoxy-luteolin-7-glucoside (3), β-sitosterol (4), 2′-hydroxy-5′-methoxybiochanin A (5) and coniferyl aldehyde (6), were isolated from Salvia plebeia and identified by UV, IR, Mass, 1H and 13CNMR spectra. Their antioxidant activities were investigated individually and compared with butylatedhydroxytoluene (BHT) (8) and α-tocopherol (7) by the oxidative stability instrument (OSI) at 100°C. Compounds 3, 4 and 5 had strong antioxidant activities, but compounds 1, 2 and 6 had low antioxidant activities at 0.02 and 0.04% levels.