Galloyl Glucoses from the Seeds of Cornus officinalis with Inhibitory Activity against Protein Glycation, Aldose Reductase, and Cataractogenesis ex Vivo

In an ongoing project directed toward the discovery of novel treatments for diabetic complications from traditional herbal medicines, six galloyl glucoses, 1,2,3-tri-O-galloyl-beta-D-glucose (1), 1,2,6-tri-O-galloyl-beta-D-glucose (2), 1,2,3,6-tetra-O-galloyl-beta-D-glucose (3), 1,2,4,6-tetra-O-galloyl-beta-D-glucose (4), 1,2,3,4,6-penta-O-galloyl-beta-D-glucose (5), and tellimagrandin II (6), and two phenolic acids, gallic acid 4-O-beta-D-glucoside (7) and gallic acid 4-O-beta-D-(6'-O-galloyl)-glucoside (8), were isolated from an EtOAc-soluble fraction of the seeds of Cornus officinalis (Cornaceae). The structures of the compounds were identified using physical and spectroscopic methods, as well as by comparison of their data with values reported in the literature. All the isolates were evaluated in vitro for inhibitory activity against the formation of advanced glycation end-products (AGEs) and rat lens aldose reductase (RLAR). Compounds 1-6 were subjected to further bioassay to examine their inhibitory effects on AGE cross-linking. The opacity of lenses was significantly prevented when treated with 3 in an ex vivo experiment.