Flavanoids of Dalea searlsiae: A plant under investigation for reintroduction to native habitats of the great basin

The plant genus Dalea (Fabaceae) has been a prolific source of phenolic metabolites. We report here an investigation of Dalea searlsiae, an herbaceous member of the genus, native to the Great Basin areas of the Western United States. D. searlsiae is the subject of current studies on the reintroduction of native flora, via seed distribution, to rangelands. Cattle that graze on these species avoid 'bloat,' which may be attributed to the high phenolic content of the plants. Methanolic extracts of aerial and root portions of the plants have undergone fractionation using standard open-column techniques of silica gel vacuum liquid chromatography, Sephadex LH-20, and linear gradient chromatographic techniques. To date, these studies have afforded a suite of isoflavones and rotenoids from the aerial portions of the plant and related phenolic materials from the roots. Structure determination of pure compounds was accomplished primarily by extensive 1D and 2D NMR spectroscopy, and mass spectrometry. Antimicrobial bioassays have revealed significant activity concentrated in the root portions of the plant. D. searlsiae is active against wild-type and penicillin-induced resistant strains of Staphylococcus aureus, and toward Streptococcus mutans and Bacillis subtilis. The results of antiinsectan assays of the rotenoid-containing aerial portions will also be presented.