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Molecules 2014, 19(9), 13027-13041; doi:10.3390/molecules190913027

Structures of New Phenolics Isolated from Licorice, and the Effectiveness of Licorice Phenolics on Vancomycin-Resistant Enterococci

1
Department of Natural Product Chemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Tsushima-naka, Kita-ku, Okayama 700-8530, Japan
2
Faculty of Pharmacy, Al-Azhar University, Assiut 71524, Egypt
3
Drug Discovery and Technology Center, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Tsushima-naka, Kita-ku, Okayama 700-8530, Japan
*
Author to whom correspondence should be addressed.
Received: 19 June 2014 / Revised: 19 August 2014 / Accepted: 20 August 2014 / Published: 25 August 2014
(This article belongs to the Section Natural Products)
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Abstract

Licorice, which is the underground part of Glycyrrhiza species, has been used widely in Asian and Western countries as a traditional medicine and as a food additive. Our continuous investigation on the constituents of roots and stolons of Glycyrrhiza uralensis led to the isolation of two new phenolics, in addition to 14 known compounds. Structural studies including spectroscopic and simple chemical derivatizations revealed that both of the new compounds had 2-aryl-3-methylbenzofuran structures. An examination of the effectiveness of licorice phenolics obtained in this study on vancomycin-resistant strains Enterococcus faecium FN-1 and Enterococcus faecalis NCTC12201 revealed that licoricidin showed the most potent antibacterial effects against both of E. faecalis and E. faecium with a minimum inhibitory concentration (MIC) of 1.9 × 10−5 M. 8-(γ,γ-Dimethylallyl)-wighteone, isoangustone A, 3'-(γ,γ-dimethylallyl)-kievitone, glyasperin C, and one of the new 3-methyl-2-phenylbenzofuran named neoglycybenzofuran also showed potent anti-vancomycin-resistant Enterococci effects (MIC 1.9 × 10−5–4.5 × 10−5 M for E. faecium and E. faecalis). The HPLC condition for simultaneous detection of the phenolics in the extract was investigated to assess the quality control of the natural antibacterial resource, and quantitative estimation of several major phenolics in the extract with the established HPLC condition was also performed. The results showed individual contents of 0.08%–0.57% w/w of EtOAc extract for the major phenolics in the materials examined. View Full-Text
Keywords: licorice; Glycyrrhiza uralensis; flavonoid; 2-aryl-3-methylbenzofuran; VRE; antibacterial effect; HPLC licorice; Glycyrrhiza uralensis; flavonoid; 2-aryl-3-methylbenzofuran; VRE; antibacterial effect; HPLC
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MDPI and ACS Style

Eerdunbayaer; Orabi, M.A.A.; Aoyama, H.; Kuroda, T.; Hatano, T. Structures of New Phenolics Isolated from Licorice, and the Effectiveness of Licorice Phenolics on Vancomycin-Resistant Enterococci. Molecules 2014, 19, 13027-13041.

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