Phenolic Constituents of Liquorice. VII. A New Chalcone with a Potent Radical Scavenging Activity and Accompanying Phenolics from Liquorice.

Twenty-three phenolics including six new compounds were isolated from a commercial liquorice from North-eastern China. Structures 2-7 were assigned for the new compounds, designated as tetrahydroxy-methoxychalcone, isolicopyranocoumarin, glycyrrhiza-flavonol A, and glycyrrhiza-isoflavones A, B and C, respectively. Compound 2 showed the most potent scavenging effect on 1, 1-diphenyl-2-picrylhydrazyl radical among the tested polyphenols isolated from liquorice. Air-oxidation of 2 in alkaline dimethylsulfoxide solution gave strong ESR signals, indicating the stability of the radical species formed from 2.