Biflavones of Dioon,

Abstract

Seven biflavones, amentoflavone, bilobetin, sequoiaflavone, ginkgetin, sciadopitysin, 7,4 Œ,7 Œ,4triple prime-tetra-O-methylamentoflavone, and diooflavone (amentoflavone hexamethyl ether), were identified from extracts of the cycad genus Dioon. The biflavones were identified by direct comparison with authentic samples using m.m.p., co-chromatography in 3 solvents, and NMR studies of the acetates. This is the first time amentoflavone hexamethyl ether has been identified as a natural product. After surveying numerous species of the Cycadales, no evidence could be obtained for the occurrence of biflavone glycosides or of biflavones based upon any other nucleus than apigenin.