Optimizing the Extraction of Bioactive Compounds from Leaves of Gymnema Lactiferum, an Edible Green Leafy Vegetable

Gymnema lactiferum is a leafy vegetable which contains phenolics and carotenoids and also possesses many health benefits such as antidiabetic properties. Response surface methodology (RSM) has been used to optimize the extraction parameters for the recovery of total phenolic compounds and carotenoids from leaves of Gymnema lactiferum. Solvent concentration (30-100%), extraction temperature (30-60°C) and extraction time (30-90 min) were used as the independent variables. A three-factor inscribed central composite design (CCD) was used to identify the relationship existing between the response functions (total phenolics and carotenoids) and the process variables, as well as to determine those conditions that optimised the extraction process of total phenolics and carotenoids contents of the extracts. A second order polynomial model produced a satisfactory fitting of the experimental data with regard to total phenolics (R2 = 86.75%, p < 0.002) and carotenoid (R2 = 84.74, p < 0.017) contents. The optimum extraction conditions of ethanol concentration, extraction temperature and extraction time for phenolics, were 19.2%, 70.2°C and 98.2 min for phenolics and 100%, 70.20°C and 110.5 min for carotenoids. The experimental values for total phenolics were 4.01±0.74 mg gallic acid equivalent (GAE) g extract and 3.56±0.19 mg/g dry weight (DW) carotenoids and no significant difference (p < 0.05) was found between the experimental and predicted values of the extractable phenolics and carotenoids