Isolation of flavonoids, a biscoumarin and an amide from the flower buds of Daphne genkwa and the evaluation of their anti-complement activity.

As part of an ongoing study aimed at identifying the anti-complement active compound from the flower buds of Daphne genkwa, ten flavonoids, one biscoumarin and one amide were isolated. Their structures were identified from spectroscopic and physicochemical data as genkwanin 5-O-beta-d-primveroside (1), apigenin 7-O-beta-d-glucuronide (2), genkwanin 5-O-beta-d-glucopyranoside (3), apigenin 5-O-beta-d-glucopyranoside (4), genkwanin (5), apigenin (6), luteolin 7-methyl ether (7), luteolin (8), daphnoretin (9), velutin (10), 7-methoxyacacetin (11) and aurantiamide acetate (12). Among them, compounds 9, 10 and 12 were isolated from this plant for the first time. The anti-complement activity of these compounds was tested against the classical pathway of the complement system. Among the compounds, daphnoretin (9) exhibited significant anti-complement activity with an IC(50) value of 11.4 microm, whereas the other compounds were not active in the assay.