Tannins and related compounds. XII. Isolation and characterization of galloylglucoses from paeoniae radix and their effect on urea-nitrogen concentration in rat serum.
Together with 1, 2, 3, 6-tetra- and 1, 2, 3, 4, 6-penta-O-galloyl-β-D-glucoses, homologous series of hexa- and heptagalloylglucoses have been isolated from the tannin fraction of the root of Paeonia lactiflora PALL var. trichocarpa BUNGE. (Paeoniaceae). Their structures were determined by hydrolytic studies and by comparison of the 13C-nuclear magnetic resonance (13C-NMR) spectra with that of pentagalloylglucose. Octa-deca-galloylglucoses were partially purified and their structures characterized mainly by using 13C-NMR spectroscopy. The isolation and structural studies of these galloylglucoses have shown gallotannins in Paeoniae Radix to have a 1, 2, 3, 4, 6-penta-O-galloyl-β-D-glucose core with depside galloyl groups predominantly at the C-3 and C-6 positions in the glucose residue. Normal-phase high performance liquid chromatographic analysis showed that the gallotannins are composed of tetra-undeca-galloylglucoses having an average molecular weight of 1286, corresponding to 7.3 galloyl groups per glucose molecule. The effects of hexa-deca-galloylglucoses isolated in this study on the urea-nitrogen (BUN) concentration in rat serum were examined, and all these compounds were shown to have remarkable BUN-decreasing activities.