Optimization of Essential Oil Extraction from Bitter Leaf (Vernonia Amygdalina) by Using an Ultrasonic Method and Response Surface Methodology

Abstract

Bitter leaf (Vernonia amygdalina) is a common bush or small tree that grows in tropical Africa. In the Ethiopian highland, the bitter leaf has been classified by the farmer as a versatile tree with high biomass yield and easy propagation. It is also well known in traditional medicine and nutritional use. The objective of this study was extraction and optimization of essential oil (EO) from the bitter leaf by using the ultrasonic extraction method and response surface methodology. The experiment was designed by Box–Behnken Design (BBD) with three factors to investigate the effect of sonication time (10 min to 30 min), ultrasonic power (100 to 200 W), and liquid-solid ratio (4 to 8 ml/g (ml of solvent per g of bitter leaf powder)). The significance of the process variables was analyzed using analysis of variance (ANOVA), and the quadratic model was fitted to the experimental results. Thus, the independent variables, sonication time, sonication power, liquid-solid ratio, and their interactions contributed a significant effect on the yield of extraction. As the result of RSM optimization, the best yield of EO was found at sonication time (17.263 min), sonication power (150.677 W), and liquid-solid ratio (6.811 ml/g). Experiments conducted under these conditions resulted in an EO yield of (4.185% g/g). The results exhibited that the RSM and BBD were effective for optimization of studied ultrasonic process variables for the maximum yield of EO from the bitter leaf (V. amygdalina).