Chemical constituents from Piper caninum and antibacterial activity

Six flavonoids and two amides, characterized as 5,7-dimethoxyflavanone (1), 5,7-dimethoxyflavone (2), 4’,5,7-trimethoxyflavone (3), 4’-hydroxy-5,7-dimethoxyflavone (4), 5-hydroxy-7-methoxyflavone (5), 2’-hydroxy-4’,6’-dimethoxychalcone (6), N-isobutyl-(2E,4E,14Z)-eicosatrienamide (7) and N-isobutyl-15-(3’,4’-methylenedioxyphenyl)-2E,4E,12E-pentadecatrienamide (8) have been isolated and identified from the stem of Piper caninum. The identification of all compounds was achieved by physical properties and spectroscopically. These data were also confirmed by comparison with previously reported spectral data. Antibacterial activity of the extracts and isolated compounds was determined by disc diffusion method and minimum inhibitory concentration (MIC). All of the extracts displayed weak antibacterial activity against the tested bacteria. Compound (7) showed good activity towards Bacillis subtilis with MIC value of 125 μg/mL. Flavonoid compounds with high content in P. caninum can probably be used as a chemical marker for this Piper species.