Essential oils, phytochemicals and bioactivities of piper caninum blume

Abstract

The chemical compositions of the essential oils and phytochemicals of Piper caninum have been studied. The essential oils were obtained by hydrodistillation technique using Dean-stark apparatus from fresh leaves and stems. The oils were analyzed by capillary GC and GC-MS. The chemical compositions were identified by comparison of the mass spectral data of Wiley Library and Kovats Indices with literatures. A total of 48 components were identified in the leaves (77.9%) and stems (87.0%) of P. caninum which were characterized by their high content of safrole (17.1-25.5%). Extractions by soxhlet apparatus were carried out on the dried samples of P. caninum to get the crude extracts. Purification of the stems and leaves extracts of P. caninum by chromatographic techniques yielded eight compounds. Their structures were elucidated spectroscopically as 5,7-dimethoxyflavone, 4',5,7-trimethoxyflavone, N-isobutyl-(2E, 4E,14E)-eicosatrienamide, N-isobutyl-15-(3',4'-methylenedioxyphenyl)-2E, 4E, 12Z-pentadecatrienamide, 5,7-dimethoxyflavanone, 4'-hydroxy-5,7-dimethoxy-flavone, 5-hydroxy-7-methoxyflavone and 2'-hydroxy-4',6'-dimethoxychalcone. Antibacterial and antioxidant studies were carried out on the essential oils, crude extracts and isolated compounds. The antibacterial assay was done by using disc diffusion method, followed by minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC) determinations. The leaves oil of P. caninum showed the highest activity towards Escherichia coli with MBCvalue 125 μg/mL. N-isobutyl-15-(3',4'-methylenedioxyphenyl)-2E,4E,12Z-pentadecatrienamide showed the highest antibacterial activity with MIC value of 125 Lig/mL against Bacillus subtilis. The methanol extracts showed the highest value of gallic acid and (±)-catechin equivalents for stem extract. This results correlated with the antioxidant assays on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical which showed that the methanolic stems extract of P. caninum had the highest radical scavenging activity with IC50 values of 802.66 Lig/mL, respectively. The isolated compounds, 4'-hydroxy-5,7-dimethoxyflavone and 5-hydroxy-7-methoxyflavone showed weak activity with IC50 values more than 1000 μg/mL.