Solvent-free Microwave-assisted Extraction of Essential Oil and Hydrosol from Piper longum Linn. Fruit and Evaluation of Antioxidant Activities

Abstract

In this study, essential oil (EO) of Piper longum Linn. fruit was isolated by solvent-free microwave-assisted extraction (SFME) and hydrodistillation (HD) with hydrosols obtained as a by-product. Optimal conditions of SFME to get a maximum EO yield were optimized applying the Box-Behnken design. Chemical compositions and anti-oxidative activities of the obtained EOs and hydrosols were also determined. Results indicated that the maximum isolation rate of EO by SFME under the optimal conditions (microwave irradiation power 572 W, microwave irradiation time 37.37 min, and percentage humidity of the matrix 59.00 %) was 0.75 %, which was significantly higher than 0.50 % by HD method. GC-MS analysis indicated that the EOs isolated by the SFME and HD methods, presented 50 and 36 compounds constituting 95.99 % and 98.52 % of the total peak area, respectively. The principal components of both oils were sesquiterpenes and aliphatics. SFME EO contained more terpenoids than HD EO. The predominant components of SFME and HD hydrosols were eugenol (25.44 % and 22.82 %, respectively) and linalool (14.10 % and 22.37 %, respectively). Trans-isoeugenol, observed for the first time in P. longum fruit, was presented in SFME hydrosol and took up 14.33 % of all the detected compounds. Both the EO and hydrosol extracted by SFME possessed better antioxidant properties than those from the HD method, which indicated that SFME was a superior approach to simultaneously obtain the two products.