Effect of coumestrol on bone metabolism in organ culture.

Coumestrol, a representative phytoestrogen, inhibited bone resorption-stimulating agent-induced bone resorption, whereas it did not inhibit basal bone resorption of cultured fetal rat limb bone. Coumestrol increased the calcium content of 9-d-old chick embryonic femurs in organ culture, indicating that this phytoestrogen stimulated bone-mineralizing activity. Therefore, coumestrol is a unique substance in that it inhibits bone resorption and, at the same time, stimulates bone mineralization. Coumestrol exhibited less estrogenic activity than 17 beta-estradiol as estimated by the increase in uterine weight of ovariectomized rats. As coumestrol has less estrogenic activity than 17 beta-estradiol, it may prove to be a more potent drug against bone diseases including osteoporosis.