Anti-Oxidative Constituents from Leonurii Herba (Leonurus japonicus).

Two new phenolic compounds, 1-O-(2,6-dimethoxy-4-hydroxyphenyl)-β-D-glucopyranoside, named leonuriside A and β-(3,4-dihydroxyphenyl)-ethyl-O-α-L-arabinopyranosyl-(1→2)-α-L-rhamnopyranosyl)-(1→3)-D-glucopyra-noside, named leonuriside B were isolated from Leonurii Herba (dried whole part of Leonurus japonicus) along with four known flavonol glycosides, rutin, isoqeurcitrin, tiliroside and isorhamnetin 3-O-rutinoside, and a known iridoid glycoside, leonuride. Their structures were elucidated on the basis of physical and spectroscopic data. Subsequent anti-oxidative assay of these compounds using the ferric thiocyanate method revealed that they, except for leonuride, have stronger anti-oxidative activities than that of α-tocopherol. Moreover, the four flavonol glycosides and leonuriside A were identified as stronger antioxidants than 3-tert.-butyl-4-hydroxyanisole.