Suppressive effect of norzoanthamine hydrochloride on experimental osteoporosis in ovariectomized mice.

Norzoanthamine is an alkaloid isolated from a colonial zoanthid. We examined the effects of norzoanthamine hydrochloride on bone weight, strength and morphology in ovariectomized mice, a postmenopausal osteoporosis model. Norzoanthamine hydrochloride significantly suppressed the decrease in femoral weight and bone biomechanical parameters caused by ovariectomy without an increase in uterine weight. This means that norzoanthamine hydrochloride does not have an estrogen-like effect on reproductive organs. Morphological observations of longitudinally ground sections of the humeri showed that norzoanthamine hydrochloride administration (2 mg/kg/d, p.o.) completely suppressed the loss of trabecular bone. Furthermore, norzoanthamine hydrochloride thickened the cortical bone. Based on these results, norzoanthamine hydrochloride may act as both a suppressor of bone resorption and an enhancer of bone formation in vivo.