Flavonoids from Sophora moorcroftiana and their synergistic antibacterial effects on MRSA

Shuang‐Ying Wang, Zhong‐Lin Sun, Tao Liu, Simon Gibbons, Wen‐Ju Zhang, Mu Qing

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Synergy is now a widely recognized approach that has direct applicability for new pharmaceuticals. The ethanolic extract of the aerial parts of the herb Sophora moorcroftiana showed significant antibacterial activity against drug-resistant Staphylococcus aureus, and its minimum inhibitory concentration (MIC) was 8 µg/mL. In a phytochemical study of the extract, five flavonoids were obtained. However, the isolates exhibited antibacterial activity in the range of 32-128 µg/mL, which was weaker than the extract. In combination with antibiotics, the antibacterially inactive compound genistein (1) and diosmetin (4) showed significant synergistic activity against drug-resistant S. aureus. In combination with norfloxacin, genistein (1) reduced the MIC to 16 µg/mL and showed synergy against strain SA1199B with a fractional inhibitory concentration index (FICI) of 0.38. With the antibiotics norfloxacin, streptomycin and ciprofloxacin, diosmetin (4) showed synergy against SA1199B, RN4220 and EMRSA-15, with FICI values of 0.38, 0.38 and 0.09, respectively. In an efflux experiment to elucidate a plausible mechanism for the observed synergy, genistein showed marginal inhibition of the NorA efflux protein.
Original languageEnglish
Pages (from-to)1071-1076
Number of pages6
JournalPhytotherapy Research
Issue number7
Early online date12 Dec 2013
Publication statusPublished - Jul 2014

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