Tannins and related compounds. Part 5. Isolation and characterization of polygalloylglucoses from Chinese gallotannin

Abstract

Along with 1,2,3,4,6-penta-O-galloyl-β-D-glucose, the homologous series of hexa- and hepta-galloylglucoses have been isolated from Chinese gallotannin, and their structures established on the basis of ¹³C n.m.r. spectroscopic analysis, methanolysis, and partial hydrolysis. Octa–undeca-galloylglucoses have also been partially purified, and their structures characterized mainly by using ¹³C n.m.r. spectroscopy. From the isolation and structural studies of these galloylglucoses, Chinese gallotannin has been shown to be a mixture consisting mainly of penta–undeca-galloylglucoses which have depside galloyl group(s) randomly distributed at the C-2, C-3, and C-4 position(s) on a penta-O-galloyl-β-D-glucose core. The evidence for the occurrence of m- and p-depside linkages in a galloyl chain is also described.