Antigiardial activity of isoflavones from Dalbergia frutescens bark

Several isoflavones [formononetin (1), castanin (5), odoratin (6), glycitei n (7), pseudebaptogenin (8), fujikinetin (9), and cuneatin (10)] were isola ted from Dalbergia frutescens, and their antiprotozoal activities were dete rmined against Giardia intestinalis. Among these compounds, formononetin (1 ) was the most potent antigiardial agent, with an IC50 value of 30 ng/mL (a pproximately 0.1 muM), as compared to the value for metronidazole, the curr ent drug of choice, of 100 ng/mL (approximately 0.6 muM). Three isoflavones closely related to formononetin [daidzein (2), biochanin A (3) and geniste in (4)] were also evaluated, but they were at least 100 times less active t han 1. Formononetin (1) may thus be an interesting lead for development of new antigiardial agents eras a probe for a new mechanistic target.