TLC-contact bioautography and disc diffusion method for investigation of the antibacterial activity of Melastoma malabathricum L. leaves

The emergence of multi-resistant strains of bacteria reinforces the need to discover new antibacterial agents that are able to combat resistant microorganisms. Medicinal plants are a valuable natural source of bioactive substances against various infectious diseases. Melastoma malabathricum L. is an important herb that is traditionally used to treat several ailments associated with microbial infection diseases such as wounds, diarrhea, dysentery, and toothache. This study investigated extracts of M. malabathricum L. for antibacterial properties against Staphylococcus aureus and Methicillin-resistant Staphylococcus aureus (MRSA). Disc diffusion and TLC-contact bioautography techniques were employed to examine antibacterial properties of n-hexane, ethyl acetate, and ethanol extracts with observations of diameter inhibition zones and Rf values. Investigation of active compounds in TLC-bioautography used several reagents including citroboric, cerium (IV) sulfate and 2,2-diphenyl-1-picrylhydrazyl (DPPH), continued by identification of chromatogram profiles through densitometry analysis. The three extracts showed good inhibition against bacterial strains with diameter inhibition zones in the range of 8.0 – 14.0 mm with a number of active spots on TLC-contact bioautography for each extract. This plant may serve as useful source of antibacterial agents for resistant microorganisms and further investigation is needed of its bioactive pure compounds as well as their particular therapeutic potentials and applications.