6,8-Diprenylgenistein

In vitro antimicrobial activities of 1-methoxyficifolinol, licorisoflavan A, and 6,8-diprenylgenistein against Streptococcus mutans.[Pubmed:25531232]

Caries Res. 2015;49(1):78-89.

The objective of the study was to investigate the antimicrobial effects of purified single compounds from ethanol-extracted licorice root on Streptococcus mutans. The crude licorice root extract (CLE) was obtained from Glycyrrhiza uralensis, which was subjected to column chromatography to separate compounds. Purified compounds were identified by mass spectrometry and nuclear magnetic resonance. Antimicrobial activities of purified compounds from CLE were evaluated by determining the minimum inhibitory concentration and by performing time-kill kinetics. The inhibitory effects of the compounds on biofilm development were evaluated using crystal violet assay and confocal microscopy. Cell toxicity of substances to normal human gingival fibroblast (NHGF) cells was tested using a methyl thiazolyl tetrazolium assay. Chlorhexidine digluconate (CHX) was used in the control group. Three antimicrobial flavonoids, 1-methoxyficifolinol, licorisoflavan A, and 6,8-Diprenylgenistein, were isolated from the CLE. We found that the three flavonoids and CHX had bactericidal effects on S. mutans UA159 at the concentration of >/=4 and >/=1 microg/ml, respectively. The purified compounds completely inhibited biofilm development of S. mutans UA159 at concentrations over 4 mug/ml, which was equivalent to 2 mug/ml of CHX. Confocal analysis showed that biofilms were sparsely scattered in the presence of over 4 mug/ml of the purified compounds. However, the three compounds purified from CLE showed less cytotoxic effects on NHGF cells than CHX at these biofilm-inhibitory concentrations. Our results suggest that purified flavonoids from CLE can be useful in developing oral hygiene products, such as gargling solutions and dentifrices for preventing dental caries.

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 activity of flavonoids from the stem bark of Erythrina caffra thunb.[Pubmed:20623615]

Phytother Res. 2011 Jan;25(1):46-8.

The antibacterial activity of the stem bark of Erythrina caffra Thunb. was investigated against different bacterial strains. The antibacterial activity was determined by a micro broth dilution assay. Antibacterial compounds were isolated and identified using a Bruker Avance III LPO NMR spectrometer. Four known flavonoids, abyssione-V 4'-O-methyl ether, 6,8-Diprenylgenistein, alpinumisoflavone and burttinone, were isolated. All the compounds were active against both Gram-negative and Gram-positive bacteria. The minimum inhibitory concentration values obtained (MIC) ranged from 3.9 mug/mL to 125 mug/mL. This is the first report of antibacterial activity of burttinone and the isolation of these compounds from E. caffra.