Studies on zoapatle. V. Correlation between in vitro uterine and in vivo pregnancy interruption effects in guinea pigs.

The zoapatle plant, Montanoa tomentosa, has an extensive ethnomedical history of use in fertility regulation. Several fractions and isolates of this plant were evaulated in in vitro and in vivo tests to identify and characterize active constituents which may be responsible for its antifertility effects. The guinea pig was the animal model. Two types of in vitro activity were observed, a uterotonic type effect and an inhibition of spontaneous contractions of the uterine muscle. The in vivo effects appear to correlate with the ability of a fraction/isolate to inhibit the spontaneous contractions in in vitro testing. The non-polar fractions/isolates accounted for the inhibition of spontaneous contraction effects and the in vivo activity. The more polar fractions/isolates accounted for the uterine stimulant activity.