Phytochemicals, essential oils and antioxidant activity from Piper ornatum N.E.Br and Piper penangense C.DC. (PIPERACEAE)

The purpose of the study was to investigate phytochemicals, essential oils, and antioxidant activity from Piper ornatum N.E.Br and Piper penangense C.DC (Piperaceae). The essential oils were obtained by hydrodistillation technique and their compositions were evaluated by gas chromatography (GC-FID) and gas chromatography-mass spectrometry (GC-MS). Isolation of phytochemicals was carried out through cold extraction of the leaves followed by separation using chromatographic techniques. The isolated compounds were confirmed by spectroscopic data and comparison with literature. The antioxidant activity of the essential oils, crude extracts, and phytochemicals were evaluated using the total phenolic content (TPC) and DPPH free radical scavenging assays. The study showed that the essential oil of P. ornatum consists of caryophyllene oxide (31.5%), sphatulenol (5.9%), aromadendrene (4.9%), and _-caryophyllene epoxide (4.5%). The major components of P. penangense essential oil were humulene epoxide II (31.9%), caryophyllene oxide (9.9%), muurola-4,10(14)-dien-1-ol (9.1%), and _-ionone (8.3%). Isolation and purification of leaves extracts from P. ornatum yielded six compounds, namely; 5,7-dimethoxyflavone (143), 4',7-dihydroxy-3',5',5- trimethoxyflavone (285), piperine (47), _-sitosterol (286), 4'-hydroxy-3',5',5,7-tetramethoxyflavone (287), and 3',4',5,5',7-pentamethoxyflavone (288). Three compounds were isolated from P. penangense which are 4-allyl resorcinol (289), chavibetol (63), and dillapiole (33). The methanolic leaf extract of P. penangense showed good antioxidant activity with high phenolic content (360.8 mg GAE/g) and percentage inhibition of DPPH radical scavenging (67.3%). Furthermore, 4-allyl resorcinol (289) showed the highest activity in the DPPH assay with percentage inhibition of 51.0%. In conclusion, the essential oils of P. ornatum and P. penangense are composed of oxygenated sesquiterpenes as their major components. Meanwhile, phytochemical studies of both Piper species yielded flavones, amide, sterols, and phenylpropanoids with significant antioxidant activity. Regarding the implication of the current study, the extracts and phytochemicals of Piper species have therapeutic potential in the prevention of free radical-related diseases such as atherosclerosis and diabetes.