RESUMEN
The present investigation describes the effect on the isolated rat ileum of methanolic extracts derived from Conyza filaginoides (D. C.) Hieron (Asteraceae), Croton fragilis HBK. (Euphorbiaceae), Dodonaea viscosa Jacq. (Sapindaceae), Gymnosperma glutinosum (Spreng) Less. (Asteraceae), Parthenium tomentosum DC. var. stramonium (Greene) Rollins (Asteraceae), Potentilla thurberi A. Gray (Rosaceae), Pterogonum atrorubens (Englem.) H. Gross (Polygonaceae), Zornia venosa Mohlenbr. (Fabaceae) and Datura lanosa Barclay ex Bye (Solanaceae). In all the cases the extracts inhibited, in a concentration-dependent manner, the spontaneous contraction of the intestinal smooth muscle. The most active extract was that of D. viscosa. These findings tend to support the ethnomedical use of the selected species as spasmolytic agents in Mexican traditional medicine. Additionally, the potential antimicrobial activity of the extracts against pathogenic enterobacteria was investigated. Seven of the nine plants evaluated displayed antibacterial effects.