Abstract

• The fruit of Piper longum L. (Peik-chin) used in the treatment of diarrhoea and dysentery in traditional Myanmar medicinal system was chosen for present study. The aim of the study is to isolate methyl piperate from the fruit of Piper longum L. (Peik-chin) and to screen the antibacterial activity of its crude extracts and methyl piperate. At first, four crude extracts of the sample were prepared by using various solvents; petroleum ether, ethyl acetate, 96 % ethanol and 50 % ethanol. In vitro antibacterial activity of four crude extracts was investigated against 19 bacterial strains by using agar disc diffusion method. Among the four crude extracts, the most active ethyl acetate extract was selected for isolation of active compound by column chromatographic method by using the solvent systems (v/v) PE : EtOAc (19:1, 9:1, 4:1, 1:1 ) consecutively. The isolated compound, methyl piperate (0.084 %) was identified by TLC and spectroscopic methods; Ultraviolet, Fourier transform infrared, Proton nuclear magnetic resonance spectroscopy, Electron impact mass spectrometry and then tested on 11 bacteria; Klebsiella species, Salmonella paratyphi A, Citrobacter species, Escherichia coli ATCC, Pseudomonas aeruginosa, Salmonella typhi, Escherichia coli YCH 149, Shigellaflexneri, Proteus species, Staphylococcus aureu sand Vibrio cholerae O1 by agar disc diffusion method. In addition, minimum inhibitory concentration (MIC) of methyl piperate determined by microtitre plate dilution method was 0.03 mg/mL on six tested bacteria; E. coli LT, S. epidermidis (MKL-50), S. epidermidis (MKL-68), E. coli EHEC, S. aureus and B. subtilis.