Rotenoids, isoflavones and chalcones from the stem bark of Millettia usaramensis subspecies usaramensis

Abstract

From the stem bark of Millettia usaramensis subsp. usaramensis four new 12a-hydroxyrotenoids with the unusual trans B/C ring junction ((+)-12a-epimillettosin, (+)-usararotenoid-A, (+)-12-dihydrousararotenoid-A, and (+)-usararotenoid-B), a new α-hydroxydihydrochalcone (α,4,2′-trihydroxy-4′-O-geranyldihydrochalcone), a new isoflavone, (norisojamicin), and a new cinnamyl alcohol derivative (4-O-geranylcinnamyl acetate) have been isolated and characterized. In addition, the known compounds 4′-O-geranylisoliquiritigenin, isoliquiritigenin, barbigerone, jamaicin and maximaisoflavone-G were identified. The structures were determined on the basis of spectroscopic evidence and chemical transformations.

New rotenones, isoflavones and dihydrochalcones have been obtained from the stem bark of Millettia usaramensis (Leguminosae) and identified by spectroscopic analysis. Novel 12a-hydroxyrotenoids are shown to have 6aR,12aS (6a-β, 12a-α) stereochemistry