ABSTRACT
Aim: To investigate antimethicillin-resistant Staphylococcus aureus (MRSA) activity of E. japonica leaf and to elucidate its anti-MRSA mechanism. Methodology: Methanolic extract of dried E. japonica leaf was partitioned in n-hexane, dichloromethane, ethyl acetate (EtOAc) and n-butyl alcohol. Antibacterial activity of extracts was determined by disk diffusion assay and minimum inhibitory concentration.Total RNA isolation was performed by treating MRSA culture with EtOAc sub-fractions. All MRSA isolates were tested for the presence of genes by reverse transcription polymerase chain reaction, followed by Western Blot. Results: The highest MRSA activity was observed from EtOAc sub-fraction 03 of methanolic extract. The minimum inhibitory concentration values of EF03 ranged from 32 to 64 µg ml-1 against methicillin-susceptible and -resistant S. aureus. EF03 fractions inhibited the expression of resistant genes in a dose-dependent manner. Moreover, the results of Western Blot assay indicated that the EF03 fractions inhibited the expression levels of resistant protein, PBP2a in a dose-dependent manner. Interpretation: EtOAc soluble fraction of E. japonica leaf evidenced profound antimicrobial activity, and inhibited expression of resistant genes against MRSA.