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The antifungal effects of leaf powders, extracts, and fractions of Cestrum nocturnum from Morelos state, Mexico, were evaluated on three isolates of Rhizopus stolonifer using mycelial inhibition bioassays. A dose-effect curve at concentrations of 0.5, 2, 5, and 10 mg/mL was observed in isolates from Cuautla and San Carlos. Leaf powders had a significant inhibitory effect from 10 to 44%. Ethanolic and aqueous extracts did not have effect on mycelial inhibition in any of the isolates at the three rates tested. Acetonic extracts had an inhibitory effect from 2 to 22%. Methanolic extracts had a significant inhibitory effect on isolates from Cuautla (18 and 62%) and San Carlos (14 and 76%), respectively, at 5 and 10 mg/mL. The isolate from Yautepec showed a greater effect at the three rates tested with a mycelial inhibition from 46 to 94%. The methanolic extract was subjected to chromatography column, where two fractions 8-11 and 12-19 were isolated; these showed mycelial growth inhibition from 6 to 66% and from 8 to 50%, respectively, on the three isolates of R. stolonifer. A preliminary study showed that these fractions corresponded to steroidal saponins. [ABSTRACT FROM AUTHOR]