The in vitro biological effects of polar extracts of Mimosa tenuiflora (Willd.) Poir. trunk bark (tepescohuite) were studied. Ethyl acetate extract, with a high tannin content, inhibited the growth of different microorganisms. Alkaloids were particularly abundant in the butanol extract and this product strongly inhibited the intestinal peristalsis and produced contraction of uterine and gastric strips of rat and guinea pig. Saponins were detected in butanol and methanol extracts producing hemolysis. The screenings performed showed the diversity of bioactive compounds present in this plant product.