Antimicrobial activity of Senna alata extract against Methicillin-Sensitive Staphylococcus aureus and Methicillin-Resistant Staphylococcus aureus

Introduction: Skin infection is a common public health problem mostly caused by Staphylococcus aureus . Senna alata (Caesalpinioideae) is a Thai herb traditionally used for bacterial skin infection. The objective of this study were to determine antimicrobial activity of the S.alata extract on Methicillin-Sensitive S. aureus (MSSA) and Methicillin-Resistant S. aureus (MRSA). Materials and M ethod: Antimicrobial activity of the herb against MSSA and MRSA was determined using agar well diffusion. Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) were determined by microdilution method. In addition the content of the chemical markers, i.e. , total phenolic, flavonoids, and anthocyanin contents, and tannin contribution of the extract were analyzed. Results: The methanolic extract showed the highest antimicrobial activity with the lowest MIC and MBC compared to the ethanolic and aqueous extracts. MIC and MBC of the S. alata methanolic extract were 2.63±0.98 and 2.50±0.00 mg/ml for MSSA, and 2.36±1.28 and 6.87±3.75 mg/ml for MRSA, respectively. Tannin content in the methanolic extract was the highest (86.12±1.75%) showing that antimicrobial activity of the S.alata extract corresponded to the tannin contribution . On the other hand, total phenolic, flavonoids, and anthocyanin contents did not rely on their antimicrobial activity. Conclusion: These observations suggested a significant value of the methanolic extract of      S.alata as a promising antibacterial compound against MSSA and MRSA.