Synergistic Effect of Brazilein in Combination with Hygromycin-b against Staphylococcus aureus

*Department of Herbal Crop Research, NIHHS, RDA, Eumseong 369-873, Korea.**Department of Oriental Pharmacy, College of Pharmacy and Wonkwang-Oriental Medicines Research Institute,Institute of Biotechnology, Wonkwang University, Iksan 570-749, Korea.***BK21 Plus Team, Professional Graduate School of Oriental Medicine, Wonkwang University, Iksan 570-749, Korea.ABSTRACT : Methicillin-resistant Staphylococcus aureus (MRSA) is a substantial contributor to morbidity and mortality.In search of a natural products capable of inhibiting this multidrug resistant bacteria, we have investigated the antimicro-bial activity of brazilein (BRZ) isolated from Caesalpinia sappan L. (Leguminosae) against 8 different strains of Staphylococ-cus aureus (S. aureus). New antimicrobial activity was found using the minimum inhibitory concentrations (MICs), brothdilution as well as checkerboard method. Against the 8 strains, the minimum inhibitory concentrations of BRZ were in therange of 62.5-500㎍/mL. From those results we performed the checkerboard test to determine the synergism of BRZ incombination with Hygromycin-b (HgB) against 4 strains. The combined activity of BRZ and HgB against 4 strains resultedin a fractional inhibitory concentrations index (FICI) ranging from 0.18-0.5. The effect of BRZ with HgB was found to besynergistic. We found that BRZ reduced the MICs of HgB. BRZ and HgB could lead to the development of new combinationantibiotics against MRSA infection. Key Words : Antibacterial Effect, Methicillin-Resistant Staphylococcus aureus, Brazilein, Hygromycin-b