Constituents of the chinese crude drug "Sāng-Bái-Pí" (morus root bark).

From the benzene extract of the Chinese crude drug "Sāng-Bái-Pí" (Japanese name Sōhakuhi), the root barks of Morus sp. (Moraceae), a novel isoprene substituted flavanone derivative, named Sanggenon B, was isolated; its structure was shown to be I on the basis of spectral and chemical data. Sanggenon B (I) is regarded biogenetically as a variation of a Diels-Alder adduct of a chalcone derivative and a dehydroprenylflavanone derivative.