Antibacterial screening and isolation of compounds from Detarium microcarpum stem bark against methicillin resistant Staphylococcus aureus

Purpose: Infectious diseases are leading cause of death globally and a primary cause of public health concern. The most worrisome aspect of microbial infection is the emergence of resistant strains of micro-organisms to commonly available antimicrobial agents. The emergences of resistant strains have added more pressure on the need to identify new agents that may be effective against resistant microbial strains. The focus of this study was to screen the crude extract and fractions of D. microcarpum stem bark for their antibacterial effects and isolate compounds with antibacterial activities. Methods: The stem bark of Detarium microcarpum was collected, authenticated, air dried, extracted into 70% methanol. The extract was fractionated successively into n-hexane, dichloromethane and ethyl acetate. Concentrated extract and fractions were subjected to antibacterial assay using Microplate Alamar Blue Assay. Two compounds were isolated using column chromatographic techniques. The compounds were characterised using spectroscopic techniques and later subjected to antibacterial studies to determine their minimum inhibitory concentration (MIC). Results: The crude extract displayed weak antibacterial activity across the panel of test microorganisms while the fractions displayed antibacterial activity in order of decreasing polarity. Compounds isolated from dichloromethane and ethyl acetate fractions were identified as methyl gallate (compound 1) and catechin gallate (compound 2), respectively. Interestingly compounds 1 and 2 displayed anti-MRSA activity with compound 2 (MIC of 200 µg/mL) displayed anti-MRSA activity. Conclusion: Antibacterial and chromatographic analysis of D. microcarpum stem bark led to identification of compounds active against methicillin resistant Staphylococcus. Keywords: Detarium microcarpum, Antibacterial activity Methyl gallate, Catechin gallate