Flowers of Hibiscus rosa-sinensis, a potential source of contragestative agent: II. Possible mode of action with reference to anti-implantation effect of the benzene extract.

Benzene extractives of Hibiscus rosa-sinensis flowers, administered during day 1-4 of gestation, exerted anti-implantation effect without affecting the tubal transport of zygote. On day 4, normal number of blastocyst was present in the uterus but they did not implant. However, as studied by pontamine blue reaction, it was evident that hyper-permeability of the endometrial capillaries which is the earliest known response of a receptive endometrium to any kind of deciduogenic stimulus was inhibited by the extract. The magnitude of decidualization, as assessed by weight of the traumatized uterine horn and supported by the histological pictures of the uteri was significantly lower in comparison to that of the controls. Ovarian structure exhibited signs of luteolysis. Inadequate progestational development of the endometrium due to interference with the conditioning of the uterus with progesterone during prenidatory phase of pregnancy has been suggested as the plausible cause of the extract-induced implantation failure.