Structures of Two New Flavonoids and Effects of Licorice Phenolics on Vancomycin-Resistant Enterococcus Species

Since our previous study revealed that several licorice phenolics have antibacterial effects on methicillin-resistant Staphylococcus aureus, and suppressive effects on the oxacillin resistance of MRSA, we further investigated effectiveness of licorice constituents on vancomycin-resistant Enterococcus bacteria, and purified 32 phenolic compounds



Scholarcy highlights

  • Licorice is one of the most frequently used natural drugs in Asian traditional medicines
  • Since two compounds among the phenolics isolated from licorice have not yet been characterized, their structures were established in the present study
  • The licorice phenolics were isolated from the ethyl acetate extract in the following way: the extract was subjected to countercurrent distribution with CHCl3–CH3OH–H2O, and the less polar fractions were respectively chromatographed on silica gel, ODS-gel, and MCI-gel CHP-20P, to give licoricidin, allolicoisoflavone B, 3'-(γ,γ-dimethylallyl)-kievitone, 7-O-methylluteone, kaempferol 3-O-methyl ether, and kaempferol, and fractions containing phenolics
  • Since several phenolics from licorice display potent antibacterial effects against methicillin-resistant Staphylococcus aureus, and show suppressing effects on the oxacillin resistance of MRSA, as we have reported previously, we have investigated the effect of these licorice phenolics on vancomycin-resistant Enterococcus
  • Except for linezolid almost all of the tested antibacterial standard drugs showed high minimum inhibitory concentration values against at least one of the two used strains as shown in Table 2, among the licorice phenolics examined in this study, a 2-arylcoumarin, gancaonin I
  • E. faecium, and E. faecalis, which is in agreement with the previously reported potent activity for a 2-arylcoumarin, gancaonin I
  • We have investigated the effectiveness of the thirty two licorice phenolics isolated in this study on vancomycin-resistant Enterococcus, and we found that several compounds possesses moderate to potent antibacterial activity against

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