Antimicrobial agents from higher plants. Antimicrobial isoflavanoids and related substances from Glycyrrhiza glabra L. var. typica

Bioassay-directed fractionation of Glycyrrhiza glabra L. var. typica resulted in the isolation and characterization of glabridin (I), glabrol (2), glabrene (3), 3-hydroxyglabrol (4), 4'-O-methylglabridin (5), 3'-methoxyglabridin (6), formononetin (7), phaseollinisoflavan (8), hispaglabridin A (9), hispaglabridin B (13), salicylic acid and O-acetyl salicylic acid. Of these, hispaglabridin A, hispaglabridin B, 4'-O-methylglabridin, glabridin, glabrol and 3-hydroxyglabrol possess significant antimicrobial activity in vitro; hispaglabridin A, hispaglabridin B, 3'-methoxyglabridin, 4'-O-methylglabridin 3-hydroxyglabrol, phaseollinisoflavan, salicylic acid, and O, acetyl salicylic acid are newly found in Glycyrrhiza sp.; and hispaglabridin A, hispaglabridin B, 3'-methoxyglabridin, 4'-O-methylglabridin, and 3-hydroxyglabrol are new to the literature and their structures are proposed herein.