Chemical Constituents of Alnus sieboldiana (BETULACEAE) II. The Isolation and Structure of Flavonoids and Stilbenes

Abstract

Four new flavonoids with an unsubstituted B-ring, alnusin, alnetin, alnustin, and alnustinol, isolated from Alnus sieboldiana were established to be 3,5,7-trihydroxy-6-methoxyflavone (1), 5-hydroxy-6,7,8-trimethoxyflavone (2), 5-hydroxy-3,6,7-trimethoxyflavone (3), and 3,5,7-trihydroxy-6-methoxyflavanone (15) respectively. Some previously-known flavonoids, chrysin (4), izalpinin (5), tectochrysin (6), pinocembrin (16), pinobanksin (17), strobopinin (19) and naringenin (20), and some stilbenes, pinosylvin (24), pinosylvin monomethyl ether (25), and pinosylvin dimethyl ether (26), were identified along with the above new flavonoids.