Antimicrobial Activities of Hydrophobic 2-Arylbenzofurans and an Isoflavone against Vancomycin-Resistant Enterococci and Methicillin-ResistantStaphylococcus aureus

Abstract

Eight 2-arylbenzofurans and an isoflavone isolated from medicinal plants were tested for their antimicrobial activities against vancomycin-resistant enterococci (VRE) and methicillin-resistant Staphylococcus aureus (MRSA). Among these compounds, six hydrophobic 2-arylbenzofurans (log P = 4.4-8.7) exhibited considerable antibacterial activity against five VRE strains(VanA-, VanB-, and VanC-phenotypes) (MICs = 3.13-6.25 microg/mL). Five compounds also showed antibacterial activity against ten MRSA strains (MIC80 = 3.13 microg/mL).

Antibacterial Compounds from Glycyrrhiza uralensis

“…28 Moreover, several isoflavones (flavonoids, pterocarpans, and pterocarpenes) from the plant were reported to have antibacterial activities against vancomycin-resistant enterococci (VRE) and methicillin-resistant S. aureus (MRSA). 9,10,12 The present study provides further evidence that some of the isoflavones in the roots of G. uralensis possess antibacterial activities.…”

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

“…The signal pattern in the 1 H-NMR spectrum of 31 is similar to that of glycyrol (15) except that a methoxyl signal observed in the spectrum of 15 is absent in that of compound A. Therefore, the structure of demethylglycyrol (31) was assigned for this compound.…”

“…Those fractions were purified by preparative TLC on silica gel or by preparative HPLC to give isolicoflavonol (7) [22], isoglycycoumarin (8) [23], licoarylcoumarin (9) [24], formononetin (10) [25], and 6"-O-acetylliquiritin (11) [26]. On the other hand, the remaining part of the ethyl acetate fraction was directly subjected to column chromatography on ODS-gel, and fractions from the column were further purified by column chromatography on MCI-gel CHP-20P, and by preparative HPLC or preparative TLC, to give liquiritin (12) [27], p-hydroxybenzoic acid (13), semilicoisoflavone B (14) [28], glycyrol (15) [29], glycyrin (16) [29], gancaonin I (17) [30], isoglycyrol (18) [31], liquiritigenin (19) [27], gancaonin G (20) [36], glicoricone (25) [37], glycycoumarin (26) [38], licocoumarone (27) [29], licoricone (28) [39], glyasperin D (29) [40], isoangustone A (30) [41], and two additional compounds temporarily named compounds A (31), and B (32). Since several phenolics from licorice display potent antibacterial effects against methicillin-resistant Staphylococcus aureus (MRSA), and also show suppressing effects on the oxacillin resistance of MRSA, as we have reported previously [11], we have also investigated the effect of these licorice phenolics on VRE.…”

“…Compound A (31) was methylated (see Experimental Section) to afford the methyl derivative 31a (Figure 2), which was identical with the compound obtained by methylation of the known compound glycyrol (15). The structure of demethylglycyrol (31) Hz, H-6') in the aromatic-proton region, corresponding to the isoflavone skeleton.…”

“…Worthy that antimicrobial activities of extracts of leaves and roots of Glycyrrhiza species were previously studied [13,14] against several bacterial strains including Enterococcus faecalis. Although a paper reported gancaonin I (17) as a compound with the anti-VRE effect [15], our study revealed several pure phenolic compounds from licorice should also be considered as lead compound candidates for new anti-VRE drugs, as shown below.…”