Phenolic constituents of licorice. II. Structures of licopyranocoumarin, licoarylcoumarin and glisoflavone, and inhibitory effects of licorice phenolics on xanthine oxidase

An anti-HIV (human immunodeficiency virus) phenolic constituent, licopyranocoumarin (4), and two other new phenolics named licoarylcoumarin (5) and glisoflavone (6) were isolated from Si-pei licorice (a commercial licorice; root and stolon of Glycyrrhiza sp. from the north-western region of China) using droplet countercurrent chromatography and centrifugal partition chromatography, and their structures were assigned based on chemical and spectroscopic data. Kaempferol 3-O-methyl ether (7) and licocoumarone (8) were also isolated from the licorice. The inhibitory effects of ten licorice phenolics on xanthine oxidase were examined. Licochalcone B (1), glycyrrhisoflavone (2), 8 and licochalcone A (19) showed 50% inhibition at the concentration of 1.3-5.6 x 10(-5) M.