Studies on the post-coital contraceptive mechanisms of a crude extract of Sri Lankan soft coral, Sinularia crispa

Previously, we have shown that a dichloromethane-methanol (1:1) elude extra ct (CE) of the Sri Lankan soft coral Sinularia crispa has potent post-coita l contraceptive activity in the rat. The aim of this study was to investiga te the modes of actions of the extract at a dose of 1,000 mg/kg. given oral ly. The results show that the CE possessed potent post-coital contraceptive activity when administered on days 1-3 (50%) and days 4-6 (64%) of pregnan cy but not on days 7-8 of pregnancy. It was neither oestrogenic nor antioes trogenic, nor progestogenic nor antiprogestogenic, nor gonadotrophic nor an tigonadotrophic. Further, the extract was well tolerated and did not induce vaginal bleeding. In contrast, it possessed potent uterotrophic activity b oth in rat and guinea pig isolated preparations and at low concentrations. We conclude that the CE mediates its post-coital contraception by desynchro nizing uterine blastocyst transport, thereby inhibiting implantation. Med S ci Res 27:331-334 (C) 1999 Lippincott Williams & Wilkins.