Antioxidative glycosides from the leaves of Ligustrum robustum

Phytochemical investigation of the ethanol extract of the leaves of Ligustrum robustum, monitored by a bioassay involving the hemolysis of red blood cells induced by 2,2'-azo-bis(2-amidinopropane) dihydrochloride, led to the isolation of three new glycosides, ligurobustosides M (1), N (2), and O (3), along with 10 known ones, osmanthuside B (4), osmanthuside B6 (5), acteoside (6), ligupurpuroside A (7), ligupurpuroside B (8), ligurobustoside C (9), ligurobustoside E (10), ligurobustoside I (11), cosmosiin (12), and rhoifolin (13). The structures of the new compounds were elucidated by spectroscopic methods. Seven of the glycosides showed stronger antioxidant effects than the standard, trolox.