PILIOSTIGMIN, A 2-PHENOXYCHROMONE, AND C-METHYLFLAVONOLS FROM PILIOSTIGMA-THONNINGII

Piliostigmin, a 2-phenoxychromone, and three C-methylflavonols, 6,8-di -C-methylquercetin 3-methyl ether, 6-C-methylquercetin 3,7-dimethyl et her and 6,8-di-C-methylquercetin 3,7-dimethyl ether, were isolated fro m the leaves of Piliostigma thonningii, together with the known compou nds quercetin, quercitrin, 6-C-methylquercetin S-methyl ether, 6-C-met hylquercetin 3,7,3'-trimethyl ether, 6,8-di-C-methyllraempferol 3-meth yl ether and 6,8-di-C-methyllraempferol 3,7-dimethyl ether. The struct ures of the new compounds were established by spectral methods, especi ally 2D NMR. Complete C-13 assignments using HMBC experiments are repo rted for the four latter C-methylflavonols. Copyright (C) 1996 Elsevie r Science Ltd