Iridoids from Vitex negundo var. heterophylla and their antioxidant activities

Two new iridoids (1-2) together with eight known iridoid glycosides (3-10) were isolated from the 70% EtOH extract of the dried leaves of Vitex negundo var. heterophylla. Their structures were elucidated by extensive spectroscopic analyses. Iridoid aglycones were found for the first time from this plant. All of these compounds were tested for their antioxidant activities. Among them, compound 9 showed moderate radical-scavenging effect on the stable free radical, 1,1-diphenyl-2-picrylhydrazyl, with IC50 values of 26.95 μM.