A bioassay-guided fractionation scheme for characterization of new antibacterial compounds from Prosopis cineraria aerial parts

BACKGROUND AND OBJECTIVES: Due to the importance of finding of new antibacterial agents, the antibacterial properties of Prosopis cineraria aerial parts were investigated using a bioassay guided fractionation scheme. MATERIALS AND METHODS: The organic extract was prepared via maceration in methanol, followed by the fractionation using n-hexane and ethyl acetate. The MICs of fractions were determined against some human pathogenic bacteria using broth micro-dilution assay. The primary characterization and identification of bioactive substance(s) was based on a bio-autographical method using HPTLC and flash chromatography in parallel with agar overlay assays. Finally the exact mass of effective compound(s) was determined by LC-MS. RESULTS: The best antibacterial activities were related to the ethyl acetate fraction. The effective antibacterial compound of the plant were 2 substances with molecular weight of 348 and 184 Dalton that inhibited the growth of assessed Gram positive bacteria with MIC values lower than 125 to 62.5 μg/ml synergistically. CONCLUSION: Further analysis using nuclear magnetic resonance could reveal the exact structure of these two antibacterial substances. These 2 effective antibacterial compounds could be applied as lead compound for synthesis of new antibacterial agents.