Application of response surface methodology to optimize the extraction of essential oil from ripe berries of Pistacia lentiscus using ultrasonic pretreatment

Abstract

Pistacia lentiscus is one of the medicinal plants that is traditionally used to cure several diseases such as asthma or burns. The present work focuses on the application of the ultrasound as pretreatment to extract essential oil from the ripe berries of this plant using the hydrodistillation process. The objective of this study was to extract essential oil from the ripe berries of this plant and optimize the extraction parameters using the Response Surface Methodology (RSM). Design Expert 9.0.6 was used to design the experiments based on the Box-Behnken Design with three parameters, namely extraction time, ultrasonic power and plant material to water ratio. The ranges of the examined independent variables (factors), i.e. the extraction time (30.60–90 h), ultrasonic power (20–60 W) and plant material to water ratio of (1:4–1:12 g dry berries per ml water) were identified by preliminary experiments. The antioxidant activity of the essential oil of P. lentiscus ripe berries was measured by different chemical assays: 2, 2- diphenyl-1-picrylhydrazyl (DPPH), 2, 2′-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging activity and reducing power. The butylated hydroxytoluene (BHT) was used as positive control. The experimental data obtained from a 17 run experiment were fitted to a second-order polynomial equation. The optimal conditions were determined by the 3D response surface and the contour plots derived from the models. Results showed that the extraction time, the ultrasonic power and the plant material to water ratio have significant effect (p < 0.001) on the yield extraction of the essential oil. The optimum extraction conditions were found to be extraction time of 60 min, ultrasonic power of 60 W and solid-liquid ratio of 1 g: 12 ml. Under the optimized conditions, the maximum value of essential oil recovery relative to the initial mass of ripe berries powder was 0.66 ± 0.03%. The antioxidant activity of the essential oil evaluated by the scavenging activity of free radicals DPPH (), ABTS (+) and reduction power showed a moderate efficiency with IC50 = 571.22 ± 1.40 mg/l, 528.87 ± 1.65 mg/l and 244.24 ± 0.41 mg/l, respectively. The essential oil of P. lentiscus ripe berries can provide good alternatives to the synthetic antioxidants, to reduce the application of synthetic compounds as antioxidants because of their potential negative health effects and as a result of consumer demand for healthy products.