Anti-HBV active flavone glucosides from Euphorbia humifusa Willd.

Thirteen flavone glucosides from the herb of Euphorbia humifusa were isolated and elucidated. Among them, five compounds including apigenin-7-O-β-D-glucopyranoside (2), apigenin-7-O-(6''-O-galloyl)-β-D-glucopyranoside (3), luteolin-7-O-β-D-glucopyranoside (7), luteolin-7-O-(6''-O-trans-feruloyl)-β-D-glucopyranoside (8) and luteolin-7-O-(6''-O-coumaroyl)-β-D-glucopyranoside (9) showed anti-HBV activity in vitro. The structure-activity relationship showed that the parent structure was closely relevant to the anti-HBV activity of these compounds (agigenin>luteolin>quercetin). It was found that the number of glucoside in the structure may significantly influence their activities (flavone monoglucoside>flavone diglucoside) and cytotoxicity (flavone>flavone monoglucoside>flavone diglucoside). In addition, the substitution of acyl group on glucoside may be important to keep the anti-HBV activities of these compounds (galloyl>feruloyl>coumaroyl).