Boerhaavia diffusa is an Ayurvedic remedy used traditionally for the treatment of a number of diseases, including those affecting the gastrointestinal tract. In the current investigation, a methanol extract obtained from roots of B. diffusa exhibited a significant spasmolytic activity in the guinea pig ileum, probably through a direct effect on the smooth muscle. A detailed phytochemical analysis of this methanol extract led to the isolation of one new (12) and six known (6-11) rotenoid derivatives. The structure of the new compound was determined through interpretation of its MS and NMR data. All the isolated rotenoids were evaluated for their effect on intestinal motility in vitro, and the results obtained showed unambiguously that they are active spasmolytic constituents. Preliminary structure-activity relationships for this class of compounds are suggested.