Antimicrobial Activity of Thespesia populnea (L.) Extracts Against Clinical Isolates of Methicillin-Resistant Staphylococcus aureus (MRSA)

Thespesia populnea L. (Family: Malvaceae) has been identified as a promising antimicrobial agent in the field of complementary medicine since time immemorial. To date, the antimicrobial activity of T. populnea against clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) has not been investigated. Here, our objective was to determine the antimicrobial activity of leaf extracts of T. populnea against clinical isolates of MRSA. Aqueous, ethanol and acetone leaf extracts of T. populnea were prepared separately following the ultrasound-assisted extraction method (40 kHz, 37 0 C, 30 minutes). The prepared extracts were tested against clinical isolates of MRSA. Bacterial susceptibility was tested using the disk diffusion assay and broth microdilution method. The activity index (AI), relative percentage inhibition (RPI), minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were estimated. Vancomycin was used as the positive control. The ethanol and acetone leaf extracts of T. populnea showed significant dose-dependent inhibitory zones (p < 0.05) signifying potent antimicrobial activity against MRSA isolates, while the best activity was shown by the acetone extract. Inhibitory zones have not appeared for the aqueous extract. Acetone extract of T. populnea showed the highest AI and RPI at 0.765 and 58.67%, respectively, and the values were significantly lower (p < 0.05) than that of the vancomycin. The MIC and MBC of the acetone extract of T. populnea against MRSA were 0.75 mg/mL. In conclusion, the results revealed that the acetone leaf extract of T. populnea exerted antimicrobial activity against clinical isolates of MRSA and could be considered a leading herbal source for the development of new antimicrobial agents.