Volatile Chemical Constituents and Bioactivity of Selected Piper Species in Sri Lanka

Abstract

The Genus Piper comprises with many economically and medicinally important species in which essential oil is one of the major secondary metabolites responsible for medicinal properties of these plants. The present study was aimed to investigate volatile chemical constituents and in vitro antibacterial, antioxidant and anti-inflammatory activities of essential oils extracted from leaves and fruits of eight Piper species found in Sri Lanka. Plant specimens were collected from natural habitats and cultivations. Essential oils were extracted using steam distillation method and subjected to gas chromatographic analysis. Identification of the volatile chemical constituents was performed by Gas chromatography mass spectrometry (GC/MS) analysis. Antioxidant activity was tested using 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay and ferric reducing power assay (FRAP). Human red blood cell (HRBC) membrane stabilizing method was used to evaluate anti-inflammatory activity. To evaluate the antibacterial activity, agar well diffusion assay was conducted for five Piper species and were tested against three pathogenic bacteria: Staphylococcus aureus ATCC 25923, Bacillus subtilis MTCC 121 and Escherichia coli ATCC 25922. As the major volatile constituents of Piper nigrum, β-caryophyllene (60.5-9.1%), caryophyllene oxide (8.49-1.3%), α-copaene (7.4-3.1%), cadina-1,(10)-4-diene (4.3-2.1%), (n)- trans-nerolidol (5.9-0.5%), 4-epi cubedol (11.0-0.5%) and β-linalool (5.7-0.7%) were identified. P. betle was dominated by safrole (39.7-33.0%) and eugenol (43.2-27.4%). Piper longum, P. chuvya and P. sylvestre contained (n)-trans-nerolidol (12.7-0.2%, 66.5% and 41.2% respectively) as the major compounds. P. betle, P. chuvya and P. longum leaves had high antioxidant activity when compared with the standard Butylated hydroxytoluene (BHT). Furthermore, P. betle exhibited high anti-inflammatory activity when compared to the standard (Aspirin). P. nigrum and P. betle showed significant antibacterial activity against S. aureus. Moreover, P. betle exhibited significant activity against B. Subtilis. The bioactivity test results revealed that some of the Piper species available in Sri Lanka are potential sources for developing new herbal drugs.