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Evidence-Based Complementary and Alternative Medicine
Volume 2013, Article ID 823794, 7 pages
Research Article

Combination Therapy of Sophoraflavanone B against MRSA: In Vitro Synergy Testing

1BK21 Plus Team, Professional Graduate School of Oriental Medicine, Wonkwang University, 344-2 Sinyong-dong, Iksan, Chonbuk 570-749, Republic of Korea
2Department of Oriental Pharmacy, College of Pharmacy and Wonkwang-Oriental Medicines Research Institute, Wonkang University, 344-2 Sinyong-dong, Iksan, Chonbuk 570-749, Republic of Korea
3Department of Herbal Crop Research, National Institute of Horticultural & Herbal Science, RDA, Eumsung, Chungbuk 369-873, Republic of Korea

Received 28 June 2013; Revised 24 September 2013; Accepted 25 September 2013

Academic Editor: Tzeng-Ji Chen

Copyright © 2013 Su-Hyun Mun et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Sophoraflavanone B (SPF-B), a known prenylated flavonoid, was isolated from the roots of Desmodium caudatum. The aim of this study was to determine the antimicrobial synergism of SPF-B combined with antibiotics against methicillin-resistant Staphylococcus aureus (MRSA). MRSA, a multidrug-resistant pathogen, causes both hospital- and community-acquired infections worldwide. The antimicrobial activity of SPF-B was assessed by the broth microdilution method, checkerboard dilution test, and time-kill curve assay. The MIC of SPF-B for 7 strains of S. aureus ranges from 15.6 to 31.25 μg/mL determined. In the checkerboard method, the combinations of SPF-B with antibiotics had a synergistic effect; SPF-B markedly reduced the MICs of the β-lactam antibiotics: ampicillin (AMP) and oxacillin (OXI); aminoglycosides gentamicin (GET); quinolones ciprofloxacin (CIP) and norfloxacin (NOR) against MRSA. The time-kill curves assay showed that a combined SPF-B and selected antibiotics treatment reduced the bacterial counts below the lowest detectable limit after 24 h. These data suggest that the antibacterial activity of SPF-B against MRSA can be effectively increased through its combination with three groups of antibiotics (β-lactams, aminoglycosides, and quinolones). Our research can be a valuable and significant source for the development of a new antibacterial drug with low MRSA resistance.