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

OBJECTIVE

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 (2-10). Compounds 2-10 were identified as amplexicine (2), catechin (3), rutin (4), quercetin-3-O-β-D-galactopyranoside (5), chlorogenic acid (6), galloyl glucose (7), caffeic acid (8), gallic acid (9) and scopletin (10).

CONCLUSIONS

Compound 1 is new. Compounds 1-10 exhibited considerable antioxidant activity in a 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging assay.