Antifertility potential of 2-[piperdinoethoxyphenyl]-3-[4- methoxyphenyl]-2H benzopyran: a potent anti-oestrogenic compound in rats.

The present study was carried out to investigate the artifertility potential of 2-[piperdinoethoxyphenyl]-3-[4-methoxyphenyl]-2H benzopyran (K-7) in rats. A single oral administration of 250 micrograms K-7 kg-1 body mass after coitus prevented pregnancy in rats. The minimum effective dose in rats given K-7 orally for 1-4 days after coitus was 100 micrograms kg-1 body mass. K-7 had weak oestrogenicity in ovariectomized immature rats but had no androgenic or anti-gonadotrophic activity. Studies in vivo showed that K-7 was a potent anti-oestrogenic compound and that at 100 micrograms kg-1 it could mitigate the effect of 1.0 microgram oestradiol. On the basis of the above results, K-7 appeared to exert its antifertility action(s) by its weak oestrogenic and its strong anti-oestrogenic activity. The anti-oestrogenic activity of K-7 was substantiated further by performing studies on the competition of K-7 for binding of [3H]oestradiol to rat uterine oestrogen receptors. A high affinity for binding to oestrogen receptors was displayed by K-7, with a relative binding affinity of 71%. These findings show that K-7 is an effective anti-oestrogenic compound and is a potent antifertility agent.