5, 6-Dihydropyranobenzopyrone: a previously undetermined antioxidant isolated from Polygonum amplexicaule

AIM: To study the chemical constituents and their bioactivity of Polygonum amplexicaule. METHODS: The isolation of compounds was achieved by chromatographic techniques and structure of the isolates was established by UV, IR, HRESI-MS and NMR including 1D and 2D experiments. RESULTS: Bioassay-guided fractionation of an ethanolic extract of Polygonum amplexicaule led to the isolation of a hitherto unidentified compound, 5, 6-dihydropyranobenzopyrone (1) along with nine previously known compounds (210). Compounds 210 were identified as amplexicine (2), catechin (3), rutin (4), quercetin-3-O--D-galactopyranoside (5), chlorogenic acid (6), galloyl glucose (7), caffeic acid (8), gallic acid (9) and scopletin (10). CONCLUSION: Compound 1 is new. Compounds 110 exhibited considerable antioxidant activity in a 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging assay.