Studies on the post-coital contraceptive mechanisms of crude extract of Sri Lankan marine red algae, Gelidiella acerosa

This study investigates the potential post-coital contraceptive mechanisms of the crude extract of Sri Lankan marine red algae, Gelidiella acerosa, using rats. The dose used was 1000 mg/kg/day and the route of administration was oral. The results showed that the crude extract possessed potent post-coital contraceptive activity when administered on days 7-8 of pregnancy indicating the presence of a narrow window in its action. The post-coital contraceptive activity was due to an elevated post-implantation loss (by 89%) resulting from fetal death between days 9-14 of pregnancy. The extract was neither estrogenic nor anti-estrogenic nor stressor but appeared to be anti-progestational (reduced ovarian progesterone output). It is suggested that the crude extract may reduce the ovarian progesterone release possibly via anti-platelet and PGE2-depressing activity.