Antibacterial Screening of Chromatographic Fractions from Dichloromethane Crude Extract of Leaves of Croton tiglium (Japala)

Abstract

Background: Plant based medicines have over the years contributed to treat diseases and illnesses. Infectious diseases have become a leading cause for premature deaths worldwide. Evidence based validation of medicinal plants is the need of the day for developing better and safe antimicrobial agents. Chromatography is a significant analytical technique that plays an important role in natural product chemistry and it helps finding new therapeutic agents. Croton tiglium is a plant belongs to the family Euphorbiaceae that has a long role as traditional medicine. Objectives: The current study was focused on the fractionation of crude ethyl acetate extract of C. tiglium, step by step visual demonstration of fractions and screening of antibacterial activity of those fractions. Methodology: Crude extract was fractionated using a silica gel column chromatography eluted with hexane and ethyl acetate in stepwise gradients with increasing polarity. Antibacterial activity was evaluated by resazurin-based broth microdilution method against three bacterial strains; Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. Results and conclusions: According to the results obtained, six fractions exhibited significant antibacterial activity against S. aureus and P. aeruginosa with minimum inhibitory concentration (MIC) in the range of 62.5- 125 µg/mL. Interestingly, four fractions showed significant activity against S. aureus while five fractions showed significant activity against P. aeruginosa. The high-performance liquid chromatography (HPLC) and nuclear magnetic resonance (NMR) data indicated the presence of low-polar metabolites in the extract; Thus, further studies are needed to isolate, purify and elucidate the structures of these metabolites.