Flavanone Glycosides from Viscum coloratum and Their Inhibitory Effects on Osteoclast Formation

Two novel flavanone glycosides, homoeriodictyol 7-O-beta-D-[6-(3-hydroxybutanoyl)glucopyranoside] (viscumneoside IX; 1) and homoeriodictyol 7-O-beta-D-[6-(3-hydroxybutanoyl) glucopyranosyl](1 --> 2)-beta-D-glucopyranoside (viscumneoside X; 2), together with four known flavanoids, 2-homoeriodictyol 7-O-beta-D-glucopyranoside (3), viscumneoside I (4), viscumneoside III (5), and 4',5-dihydroxy-3'-methoxy-7(2-O-alpha-L-rhamnopyranosyl-beta-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 mg/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.