New phenanthrene derivatives with nitric oxide inhibitory and radical-scavenging activities from Pholidota imbricata Hook.

One new phenanthrene derivative phoimbrtol A (1) with seven known compounds, loddigesiinol B (2), shanciol B (3), (-)-medioresinol (4), (-)-pinoresinol (5), quercetin 3-O-β-L-arabinofuranoside (6), luteolin 7-O-β-glucoside (7) and platycaryanin D (8) have been isolated from the ethyl acetate extract of the air-dried whole plant of Pholidota imbricata Hook. Their inhibitory effects on nitric oxide (NO) production and 1,1-diphenyl-2-picrylhydrazil (DPPH) radical scavenging activity were examined. Among these compounds, 8 exhibited the most potent activity at NO production inhibitory assay and DPPH radical scavenging assay, stronger than those of the familiar antioxidative agents, quercetin and resveratrol.