ANTIGESTAGENIC ACTIVITY OF IXORA-FINLAYSONIANA IN RAT

Oral administration of crude ethanolic extract of the serial parts of Ixora finlaysoniana Wall. ex G. Don to adult female rats at 250 mg/kg dose on days 1-5 or 1-7 post-coitum prevented pregnancy in 100% rats. The extract was also effective when administered on days 1 or 1-3 post -coitum, but the minimum effective dose increased with decreased durat ion of administration and was 1000 mg/kg and 500 mg/kg, respectively, in the two schedules. At lower doses, a significant reduction in impla ntation number and increased post-implantation resorption rate were ob served in all the schedules. Almost complete resorption of all implant ations was observed after administration of 1000 mg/kg dose of the ext ract during the peri-implantation period. A slight acceleration in tub al transport rate of embryos and delay in blastocyst formation were ob served in rats treated post-coitally with the single anti-implantation dose of the extract. Significantly fewer embryos were recovered after their entry into the uterus. Except in one rat receiving 250 mg/kg do se of the extract on-days 1-5, in which one apparently normal zona-fre e blastocyst was recovered from the uterus, uterine flushings of none of the nonpregnant animals contained any unimplanted embryos by day 10 post-coitum. In immature rat bioassay, the extract was found to posse ss estrogenic activity as evidenced by dose-dependent increase in uter ine weight and cornification of the vaginal epithelium at doses rangin g from 50-1 000 mg/kg. At the 500 and 1000 mg/kg doses, it also induce d premature opening of the vagina. Taking 100% increase in uterine wei ght as the parameter, the extract was found to be about 1.6x10(5) time s less estrogenic than ethinylestradiol. The extent and duration of es trogenic responses exerted by single contraceptive dose of the extract were also markedly lower than that induced by ethinylestradiol. The e xtract was devoid of any estrogen antagonistic or synergistic activity and did not affect ovarian prenidatory estrogen or progesterone synth esis. The findings indicate that the extract at its contraceptive dose a) exerts a differential estrogenic response at the fallopian tube an d the uterine levels, b) does not appear embryocidal, but causes sligh t asynchrony in development and tubal transport rate of pre-implantati on embryos, which together with their loss through vagina after entry into the uterus, due to estrogenic action of the extract, might contri bute to its anti-implantation action, and c) its anti-implantation and post-implantation resorptive actions are not mediated via altered ova rian function.