Optimization of essential oil extraction process from Piper nigrum L. by-products and investigation of its biological activities

Black pepper (Piper nigrum L.) is an industrial crop commonly grown in Vietnam. Besides its economic value, its processing released large amounts of by-products into the environment including leaves, flatterned seeds, and seed-bearing branches. The objective of this study was to optimize the extraction of essential oil from the mixture of three black pepper by-products and evaluate its biological activities in order to exploit the potential value of the by-products. The essential oils were extracted by hydrodistillation in which the extraction conditions including extraction time, water to feed ratio, and ultrasonic pretreated time were optimized. The results showed that the highest essential oil yield was achieved after 4 h of extraction at a water to feed ratio of 10:1, and 10 min of ultrasonic pre-treament. Isospathulenol, β-selinene, caryophyllene, α-pinene, and α-copaene were identified as the main components of the essential oil as a result of chemical composition analysis using gas chromatography mass spectrometry. The essential oils exhibited 2,2-Diphenyl-1-picrylhydrazyl radical scavenging capacity with an IC50 value of 4.205 mg/mL and antibacterial capacity against four strains of bacteria, including Bacillus spizizenii, Bacillus cereus, Staphylococcus aureus and Salmonella enterica with the diameters of inhibition zone of 11.37 mm, 4.12 mm, 7.75 mm, 5.37 mm, respectively.