The in vitro effect of grandiflorenic acid and zoapatle aqueous crude extract upon spontaneous contractility of the rat uterus during oestrus cycle.

Montanoa tomentosa (zoapatle) is a Mexican plant popularly used for antifertility purposes and with promising characteristics for the development of a new oral contraceptive agent with uteroevacuant properties. In a previous pharmacological report we established the ambivalent myometrial response to zoapatle leaves aqueous extract (ZACE) depending on the animal species used and on the existence or absence of pregnancy. This fact could be useful in determining an appropriate medical use of zoapatle and suggests an interesting possible hormonal dependence in its mechanism of action. To elucidate the ZACE effect upon the pattern of uterine contractility in different hormonal stages, the rat uterus in vitro during oestrus cycle was studied. The aqueous crude extract of Montanoa tomentosa leaves produced different (or even opposite), effects on uterine motility during the distinct phases of the oestrus cycle in the rat. Furthermore, pure grandiflorenic acid (GA), obtained from the phytochemical work up of this plant reproduced the uterine responses induced by ZACE. The action of zoapatle is discussed in relation to hormonal stage and to a probable adrenergic mechanism involved.