Flavanone glycosides from viscum coloratum and their inhibitory effects on osteoclast formation

Two novel flavanone glycosides, homoeriodictyol 7-O-β-D-[6-(3-hydroxybutanoyl)glucopyranoside] (viscumneoside IX; 1) and homoeriodictyol 7-O-β-D-[6-(3-hydroxybutanoyl)glucopyranosyl](1→2)-β-D-glucopyranoside (viscumneoside X; 2), together with four known flavanoids, 2-homoeriodictyol 7-O-β-D-glucopyranoside (3), viscumneoside I (4), viscumneoside III (5), and 4',5-dihydroxy-3'-methoxy-7-(2-O-α-L-rhamnopyranosyl-β-D-glucopyranosyloxy)flavanone (6) were isolated from stems and leaves of Viscum coloratum. Their structures were elucidated on the basis of their NMR spectra, HR-FAB-MS data, and acid hydrolysis. Inhibitory effects of the four compounds 1-4 on the formation of osteoclast-like multinucleated cells were investigated. As a result, all the four flavanoids showed significant inhibitory effects on the formation of osteoclast-like multinuclear cells even at a low concentration of 2 μg/ml. The activities of 1-4 at such a concentration exceeded or approximated to that of elcitonin, the positive control drug at a concentration of 2 U/ml, suggesting that they may be of interest for the development of new anti-osteoporosis drugs.