Essential Oils From Different Parts of <i>Piper nigrum</i> L.: Chemical Composition, Antibacterial, and Antioxidant Activities

Pepper (<i>Piper nigrum</i> L.) is a spice plant that contains bioactive compounds, including essential oils, with antioxidant and antimicrobial activity. The study intended to determine the composition of essential oil in the pepper plant's seeds, stems, as well as leaves and whether these materials had any potential antioxidant activity, and antibacterial activity against <i>Escherichia coli</i> and <i>Staphylococcus aureus</i>. GC-MS (Gas Chromatography-Mass Spectrometry) was utilized to investigate the components of pepper oil, and the inhibition diameter was used to determine the antibacterial activity. The findings revealed that 19, 19, and 29 compounds were found in pepper seed, leaf and stem essential oils, respectively. The three most important contents of seed essential oil were <i>δ</i>-3-carene (11.49%), limonene (13.35%), and <i>β</i>-caryophyllene (37.42%). Leaf essential oil contained <i>δ</i>-elemene (3.73%), <i>δ</i>-3-carene (19.03%), and <i>β</i>-caryophyllene (50.50%), while stem essential oil was dominated by <i>α</i>-selinene (11.93%), <i>β</i>-caryophyllene (12.83%), and <i>δ</i>-elemene (19.73%). Principal Component Analysis (PCA) revealed clear compositional differences among the three essential oils. Antibacterial assays showed variable activity, with inhibition zones against <i>E. coli</i> measuring 1.5 mm, 6.83 mm, and 4.83 mm, for seed, leaf, and stem oils, respectively, and against <i>S. aureus</i> measuring 8.89 mm, 8.06 mm, and 13.00 mm. Antioxidant activity, evaluated by the DPPH assay demonstrated that stem essential oil exhibited the strongest radical scavenging effect (IC₅₀ 255.10 ppm; TEAC 8.39 μmol TE/g), followed by leaf oil (IC₅₀ 358.62 ppm; TEAC 5.98 μmol TE/g) and seed oil (IC₅₀ 485.98 ppm; TEAC 4.41 μmol TE/g), though all were considered weak antioxidants. These results indicate that <i>P. nigrum</i> essential oils vary significantly in chemical composition and bioactivity across plant parts. The findings confirm their antibacterial and antioxidant potential and underscore the value of seeds, leaves, and stems as alternative sources of bioactive essential oils for prospective applications in food preservation, pharmaceuticals, and natural health products.