Phytochemicals and bioactivities of piper maingayi hk. f., p. magnibaccum c. dc. and p. caninum blume species

Abstract

The chemical compositions of the essential oils and phytochemicals of Piper maingayi Hk. F., P. magnibaccum C. DC. and P. caninum Blume were studied. The essential oils obtained by hydrodistillation from the fresh samples of P. maingayi (stem and fruit) and P. magnibaccum (stem and leaf) were analyzed by capillary gas chromatography (GC) (Kovats Indices) and gas chromatography-mass spectrometry (GC-MS). The stem and fruit oils of P. maingayi successfully afforded 34 and 18 components, respectively. The stem oil consisted of ß-caryophyllene (26.2%) and a-cedrene (8.4%) as the major components, while the fruit oil was dominated by ß-caryophyllene (39.6%) and d-cadinene (22.6%). The essential oils of leaf and stem of P. magnibaccum gave 25 and 34 constituents, respectively. Both the leaf and stem oils were rich with germacrene D (10.7-40.8%) and ß-caryophyllene (8.5-19.7%). The phytochemical study was carried out on the dried samples using maceration technique with n-hexane, dichloromethane and methanol to acquire the crude extracts. Fractionation and purification of the crude extracts using various chromatographic techniques have resulted in the isolation of eighteen compounds belonging to eight classes of phytochemicals. Those classes of phytochemicals were identified spectroscopically as aporphine alkaloids, triterpenes, fatty acids and esters, phenolic, flavonoid, amide alkaloid and lignin. ß-Sitosterol, oleic acid and cepharadione A were isolated from all the investigated species. Piperumbellactam A was isolated from P. maingayi and P. magnibaccum, linoleic acid was isolated from P. magnibaccum and P. caninum while methyl linolenate was isolated from P. caninum and P. maingayi. Six compounds were isolated exclusively from P. maingayi and elucidated as sesamin, butyl dodecanoate, isovanillic acid, cepharadione B, piperolactam A and one new unsaturated amide namely N-isobutyl-15-(18,19-methylenedioxyphenyl)-2E,4E,12Z-pentadecatrienamide. Two compounds characterised as 24S-ethylcholesta-5,22,25-trien-3ß-ol and stigmast-3,6-dione were obtained from P. magnibaccum while four compounds, namely 24-methylenecycloartan-3-one, 5,7-dimethoxyflavone, cepharanone A and aristolactam AII were revealed from P. caninum. Screenings on antibacterial, antioxidant, anti-inflammatory and antityrosinase bioactivities of the selected crude extracts, essential oils and pure compounds were also investigated. The leaf essential oil of P. magnibaccum showed a moderate antibacterial activity with MIC value of 250 µg/mL against Pseudomonas aeruginosa compared to the other oils, while N-isobutyl-15-(18,19-methylenedioxyphenyl)-2E,4E,12Z-pentadecatrienamide showed MIC value of 250 µg/mL each on B. subtillis and P. aeruginosa. The essential oil of P. maingayi and P. magnibaccum stems depicted a significant activity in DPPH assay with SC50 value of 14.9 and 17.5 µg/mL, respectively. Study on anti-inflammatory activity was carried out using 15-LOX enzymatic assay. Amide of N-isobutyl-15- (18,19- methylenedioxyphenyl)- 2E,4E,12Z- pentadecatrienamide exhibited the strongest inhibition against 15-LOX at IC50 42.52 µM. The tyrosinase inhibition activity showed moderate activity (59.6%) for P. maingayi stem oil and ethyl acetate crude extract (69.2%) each at a concentration of 1 mg/mL