Tannins and Related Compounds. XXI. Isolation and Characterization of Galloyl and p-Hydroxybenzoyl Esters of Benzophenone and Xanthone C-Glucosides from Mangifera indica L

Six new galloyl and p-hydroxybenzoyl esters (2-7) of benzophenone C-glucosides have been isolated, together with a new benzophenone C-glucoside (1), from the leaves of Mangifera indica L. (Anacardiaceae). On the basis of chemical and spectroscopic evidence, the structures of these compounds have been established as maclurin 3-C-β-D-glucoside (1), maclurin 3-C-(6"-O-p-hydroxybenzoyl)-β-D-glucoside (2), maclurin 3-C-(2"-O-galloyl-6"-O-p-hydroxybenzoyl)-β-D-glucoside (3), maclurin 3-C-(2"-O-p-hydroxybenzoyl-6"-O-galloyl)-β-D-glucoside (4), maclurin 3-C-(2", 3", 6"-tri-O-galloyl)-β-D-glucoside (5), iriflophenone 3-C-(2", 6"-di-O-galloyl)-β-D-glucoside (6) and iriflophenone 3-C-(2", 3", 6"-tri-O-galloyl)-β-D-glucoside (7). (-)-Epicatechin 3-O-gallate (9), mangiferin (10), isomangiferin (11) and a new xanthone C-glucoside gallate, mangiferin 6'-O-gallate (8), have also been isolated and their structures have been similarly characterized. Furthermore, the above plant source contained polygalloylglucoses which were characterized on the basis of chemical and high performance liquid chromatographic analyses as a mixture of penta-to undecagalloylglucoses based on a 1, 2, 3, 4, 6-penta-O-galloyl-β-D-glucose core. Maclurin 3-C-glucoside (1) has been transformed enzymatically to mangiferin (10) and isomangiferin (11), and it has become clear that 1 is a key intermediate in the biosynthesis of 10 and 11.