Antioxidative Constituents from Viticis trifoliae Fructus (Fruit of Vitex rotundifolia L.)

Seven phenolic compounds, vanillic acid (1), threo-guaiacyl glycerol (2), erythro-guaiacyl glycerol (3), taxifolin (4), dihydrodehydrodiconiferyl alcohol (5), dihydrodehydrodiconiferyl alcohol-9-O-β-D-glucoside (6) and dihydrodehydrodiconiferyl alcohol-(4→8)-erythro-guaiacyl glycerol ether (7), were separated from the methanol extract of Viticis trifoliae Fructus (Fruit of Vitex rotundifolia L.) and their structures were identified on the basis of spectroscopic data. In addition, 1, 2, 4-7 and two previously isolated iridoid glucosides, agnuside (8) and VR-I (10-O-vanilloyl aucubin) (9) were tested for antioxidative activity using the ferric thiocyanate method. These compounds, except 8, exhibited stronger antioxidative activity than 3-tert-butyl-4-hydroxyanisole. Moreover, 1, 2 and 4-9 were investigated for the scavenging effect on 1,1-diphenyl-2-picrylhydrazyl. All tested compounds, except 8, showed a potent scavenging effect. Especially, the effect of 4 was almost twice that of α-tocopherol at a concentration of 0.02 mM.