Phytochemicals and antibacterial activity of piper retrofractum vahl and piper arborescens roxb

Abstract

The phytochemical investigations of the fruits of Piper retrofractum Vahl. and the stems and leaves of Piper arborescens Roxb. have been carried out. The fruits of Piper retrofractum Vahl. were bought from a spice shop at Pandan, Johor Bahru and the methanolic crude extracts of stems and leaves of Piper arborescens Roxb. were obtained from UiTM Sarawak, Malaysia. Samples were extracted with Soxhlet extractor using methanol as the solvent to give the crude extracts. The crude extracts were fractionated using vacuum-liquid chromatography and then purified using several chromatographic techniques. The isolated compounds were identified by analysis of various spectral data using infrared, 1D (1H, 13C and DEPT) and 2D (COSY, and HMBC) nuclear magnetic resonance spectroscopies and mass spectrometry. Seven compounds were isolated from these plants. The purification of methanol crude extract of the fruits of Piper retrofractum Vahl. yielded four compounds identified as piperine, oleic acid, N-isobutyl-2E,4E,14Z-eicosatrienamide and methyl piperate. Another three compounds, characterized as sesartemin, diayangambin and 3-(3,4-dimethoxybenzyl)-4-(3',4',5'-trimethoxybenzyl)- tetrahydrofuran-2-ol had been isolated from the methanol crude extract of the stems of Piper arborescens Roxb. The hydrolysis of piperine was done using potassium hydroxide and ethanol to yield piperic acid. The antibacterial test against Gram positive bacteria (Bascillus subtilis and Staphylococcus aureus) and Gram negative bacteria (Pseudomonas aeruginosa and Escherichia coli) were performed on the crude extracts and isolated compounds. The crude extracts and piperine were found to show the strongest inhibition against both Gram positive bacteria with MIC and MBC values of 225 µg/mL.