Constituents from the leaves of Phellodendron amurense and their antioxidant activity

Three new coumarins, phellodenols F-H (1-3) and a new glutaric acid derivative, phellodendric acid-A (4) were isolated from the leaves of Phellodendron amurense together with twenty-nine known compounds. Extensive 1D and 2D NMR experiments and other spectroscopic studies were employed to determine the structures of 1-4. The isolated compounds were screened for their antioxidant activity through DPPH (alpha,alpha-diphenyl-beta-picrylhydrazyl) radical scavenging assay. Compounds quercetin, quercetin-3-O-beta-D-glucoside, quercetin-3-O-beta-D-galactoside and kaempferol-3-O-beta-D-glucoside demonstrated significant radical scavenging activity comparable to vitamin E.