Differences in uterotonic activity were observed between zoapatle Montanoa (Cerv.), plants growing in their natural habitat and plants growing in an experimental agricultural plot. Details of an in vitro analogic model for assaying uterotonic potency in guinea pig strips is described. Important species differences on the uterine response to zoapatle aqueous crude extract were noticed in rats, hamsters, guinea pigs, cats and Rhesus monkeys. The need for proper biological evaluation of chemical substances already isolated from zoapatle specimens, is mentioned, and the advantages of working with zoapatle specimens grown under controlled ecological conditions are pointed out.
PIP: An in vitro analogic method for comparing the uterotonic potency of dialysed zoapatle aqueous crude extract (DZ-ZACE) with oxytocin is described. Uterine strips from estrogenized guinea pigs were selected as the appropriate animal model after trials with estrogenized rats, hamsters, cats, and Rhesus monkeys. Results of the in vitro uterotonic effect produced by 21 different zoapatle Montanoa plants collected from different parts of Mexico and grown in an experimental agricultural field station indicate considerable difference, with less variation in uterotonic oxytocin/equivalents among the plants grown at the field station than in wild specimens. The general reduction in uterotonic potency of plants grown at the field station may be due to differences in the time of collection: wild specimens were collected in winter 1980, while field station specimens were collected just after flowering in early summer 1981. The findings clearly demonstrate the influence of the plant environment on the expression of biological response. Because of its lack of toxicity, abundance, ease of production, and the availability of an efficient analogic in vitro assay for the evaluation of relative uterotonic potency, ZACE may eventually be the source of a new agent to intercept pregnancy.