Components of Broussonetia papyrifera (L.) Vent. I. Structures of two new isoprenylated flavonols and two chalcone derivatives.

Two new isoprenylated flavonols, broussoflavonols A and B, and two isoprenylated chalcones, broussochalcones A and B, were isolated from the benzene extract of the cortex of Broussonetia papyrifera (L.) VENT. (Japanese name "Kajinoki, " Moraceae). The structures of broussoflavonols A, B, and broussochalcone B were shown to be 1, 2, and 4, respectively, on the basis of spectral evidence, and the structure of broussochalcone A was determined to be 3 on the basis of spectral and chemical evidence.