Int. J. Mol. Sci. 2012, 13(7), 8210-8218; doi:10.3390/ijms13078210
Article

Isojacareubin from the Chinese Herb Hypericum japonicum: Potent Antibacterial and Synergistic Effects on Clinical Methicillin-Resistant Staphylococcus aureus (MRSA)

1email, 1,2email, 3email, 1email, 1email, 2email and 4,* email
Received: 7 May 2012; in revised form: 31 May 2012 / Accepted: 18 June 2012 / Published: 3 July 2012
(This article belongs to the Section Bioactives and Nutraceuticals)
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.
Abstract: Through bioassay-guided fractionation of the extracts from the aerial parts of the Chinese herb Hypericum japonicum Thunb. Murray, Isojacareubin (ISJ) was characterized as a potent antibacterial compound against the clinical methicillin-resistant Staphylococcus aureus (MRSA). The broth microdilution assay was used to determine the minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) of ISJ alone. The results showed that its MICs/MBCs ranged from 4/16 to 16/64 μg/mL, with the concentrations required to inhibit or kill 50% of the strains (MIC50/MBC50) at 8/16 μg/mL. Synergistic evaluations of this compound with four conventional antibacterial agents representing different types were performed by the chequerboard and time-kill tests. The chequerboard method showed significant synergy effects when ISJ was combined with Ceftazidime (CAZ), Levofloxacin (LEV) and Ampicillin (AMP), with the values of 50% of the fractional inhibitory concentration indices (FICI50) at 0.25, 0.37 and 0.37, respectively. Combined bactericidal activities were also observed in the time-kill dynamic assay. The results showed the ability of ISJ to reduce MRSA viable counts by log10CFU/mL at 24 h of incubation at a concentration of 1 × MIC were 1.5 (LEV, additivity), 0.92 (CAZ, indifference) and 0.82 (AMP, indifference), respectively. These in vitro anti-MRSA activities of ISJ alone and its synergy with conventional antibacterial agents demonstrated that ISJ enhanced their efficacy, which is of potential use for single and combinatory therapy of patients infected with MRSA.
Keywords: anti-MRSA activity; Hypericum japonicum; Isojacareubin; MIC; synergy
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MDPI and ACS Style

Zuo, G.-Y.; An, J.; Han, J.; Zhang, Y.-L.; Wang, G.-C.; Hao, X.-Y.; Bian, Z.-Q. Isojacareubin from the Chinese Herb Hypericum japonicum: Potent Antibacterial and Synergistic Effects on Clinical Methicillin-Resistant Staphylococcus aureus (MRSA). Int. J. Mol. Sci. 2012, 13, 8210-8218.

AMA Style

Zuo G-Y, An J, Han J, Zhang Y-L, Wang G-C, Hao X-Y, Bian Z-Q. Isojacareubin from the Chinese Herb Hypericum japonicum: Potent Antibacterial and Synergistic Effects on Clinical Methicillin-Resistant Staphylococcus aureus (MRSA). International Journal of Molecular Sciences. 2012; 13(7):8210-8218.

Chicago/Turabian Style

Zuo, Guo-Ying; An, Jing; Han, Jun; Zhang, Yun-Ling; Wang, Gen-Chun; Hao, Xiao-Yan; Bian, Zhong-Qi. 2012. "Isojacareubin from the Chinese Herb Hypericum japonicum: Potent Antibacterial and Synergistic Effects on Clinical Methicillin-Resistant Staphylococcus aureus (MRSA)." Int. J. Mol. Sci. 13, no. 7: 8210-8218.

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