Hibiscus rosa-sinensis
While the mechanism is not well understood, previous animal studies have demonstrated both an inhibitory effect of "H. sabdariffa" on muscle tone and the anti-fertility effects of "Hibiscus rosa-sinensis", respectively. The extract of "H. sabdariffa" has been shown to stimulate contraction of the rat bladder and uterus; the "H. rosa-sinensis" extract has exhibited contraceptive effects in the form of estrogen activity in rats. These findings have not been observed in humans. The "Hibiscus rosa-sinensis" is also thought to have emmenagogue effects which can stimulate menstruation and, in some women, cause an abortion. Due to the documented adverse effects in animal studies and the reported pharmacological properties, the "H. sabdariffa" and "H. rosa-sinensis" are not recommended for use during pregnancy.