Gancaonin G

Phenolic constituents of licorice. VIII. Structures of glicophenone and glicoisoflavanone, and effects of licorice phenolics on methicillin-resistant Staphylococcus aureus.[Pubmed:10993226]

Chem Pharm Bull (Tokyo). 2000 Sep;48(9):1286-92.

Two new phenolic compounds, glicophenone (1) and glicoisoflavanone (2), were isolated from commercial licorice, and their structures were elucidated on the basis of spectroscopic data. Antibacterial assays of licorice phenolics for Staphylococcus aureus, including four strains of methicillin-resistant S. aureus (MRSA), and also for Escherichia coli K12 and Pseudomonas aeruginosa PAO1, were then examined. Two compounds among them, 8-(gamma,gamma-dimethylallyl)-wighteone (21) and 3'-(gamma,gamma-dimethylallyl)-kievitone (28), showed remarkable antibacterial effects [minimum inhibitory concentrations (MICs), 8 microg/ml on the MRSA strains and methicillin-sensitive S. aureus. Licochalcone A (14), Gancaonin G (20), isoangustone A (24), glyasperins C (30) and D (31), glabridin, (32), licoricidin (33), glycycoumarin (34) and licocoumarone (40) showed antibacterial effects on the MRSA strains with MIC values of 16 microg/ml. Effects on the beta-lactam resistance of the MRSA strains were also examined, and licoricidin (33) noticeably decreased the resistance of the MRSA strains against oxacillin, as shown by the reduction in the MICs of oxacillin (lower than 1/128-1/1000 in the presence of 8 microg/ml of 33, and 1/8-1/32 in the presence of 4 microg/ml of 33). Mechanistic study suggested that 33 does not inhibit the formation of penicillin-binding protein 2' (PBP2'), but affects the enzymatic function of PBP2'.

Pyrano-isoflavans from Glycyrrhiza uralensis with antibacterial activity against Streptococcus mutans and Porphyromonas gingivalis.[Pubmed:24479468]

J Nat Prod. 2014 Mar 28;77(3):521-6.

Continuing investigation of fractions from a supercritical fluid extract of Chinese licorice (Glycyrrhiza uralensis) roots has led to the isolation of 12 phenolic compounds, of which seven were described previously from this extract. In addition to these seven metabolites, four known components, 1-methoxyerythrabyssin II (4), 6,8-diprenylgenistein, Gancaonin G (5), and isoglycyrol (6), and one new isoflavan, licorisoflavan C (7), were characterized from this material for the first time. Treatment of licoricidin (1) with palladium chloride afforded larger amounts of 7 and also yielded two new isoflavans, licorisoflavan D (8), which was subsequently detected in the licorice extract, and licorisoflavan E (9). Compounds 1-9 were evaluated for their antibacterial activities against the cariogenic Streptococcus mutans and the periodontopathogenic Porphyromonas gingivalis. Licoricidin (1), licorisoflavan A (2), and 7-9 showed antibacterial activity against P. gingivalis (MICs of 1.56-12.5 mug/mL). The most potent activity against S. mutans was obtained with 7 (MIC of 6.25 mug/mL), followed by 1 and 9 (MIC of 12.5 mug/mL). This study provides further evidence for the therapeutic potential of licorice extracts for the treatment and prevention of oral infections.

Antibacterial compounds from Glycyrrhiza uralensis.[Pubmed:16441081]

J Nat Prod. 2006 Jan;69(1):121-4.

From the roots of Glycyrrhiza uralensis, two new pterocarpenes, glycyrrhizol A (1) and glycyrrhizol B (2), along with four known isoflavonoids, 5-O-methylglycryol (3), isoglycyrol (4), 6,8-diisoprenyl-5,7,4'-trihydroxyisoflavone (5), and Gancaonin G (6), were isolated using a bioassay-guided fractionation method. The structures of the new compounds (1and 2) were elucidated by spectroscopic data interpretation. The known compounds (3-6) were identified by comparison of their spectroscopic data with reported values in the literature. Glycyrrhizol A (1) and 6,8-diisoprenyl-5,7,4'-trihydroxyisoflavone (5) exhibited potent antibacterial activity against Streptococcus mutans with minimum inhibitory concentrations of 1 and 2 microg/mL, respectively, while glycyrrhizol B (2) and Gancaonin G (6) showed more moderate activity.