Combretodendron Africanum bark extract as an antifertility agent. I: Estrogenic effects in vivo and LH release by cultured gonadotrope cells.

An aqueous extract from the stem bark of Combretodendron africanum was prepared to investigate its potency as a regulator of fertility. The intraperitoneal LD50 in mice was 95.2 +/- 4.3 mg/kg. Daily i.p. injections of 50 mg/kg promoted a significant increase in the uterine weight of 25 day-old female rats while pituitary weight remained unaffected. Similar injections for 21 days to mature females blocked the estrous cycle in the luteal phase with a mean length of efficiency of 15 days and decreased plasma LH and FSH levels. Regular cycles were restored 10 days following the last injection. C. africanum extract was shown to compete with estradiol and with progesterone on uterine receptors. Consequently, it is thought to contain substances exhibiting estrogenic (and possibly anti-estrogenic) potency. The effects of the extract on LHRH-induced release were investigated on cultured pituitary cells. Although gonadotropin release was amplified, the extract itself appeared as to be a potent secretagogue not requiring LHRH receptors. It follows that the active molecules contained in C. africanum extracts may be different from classical steroid estrogens.