Response surface optimization for recovery of polyphenols and carotenoids from leaves of Centella asiatica using an ethanol-based solvent system.

Response surface methodology has been used to optimize the extraction conditions for total phenolics and carotenoids from leaves of Centella asiatica. Solvent concentration (30%-100%), extraction temperature (30-60°C), and extraction time (30-90 min) were used as the independent variables. A second-order polynomial model produced a satisfactory fitting of the experimental data with regard to total phenolics (R 2 = 84.75%, p < 0.004) and carotenoid (R 2 = 78.74, p < 0.019) contents. The optimum extraction conditions of ethanol concentration, extraction temperature, and extraction time for phenolics were 6.1%, 70.2°C, and 110.5 min and for carotenoids, the optimum parameters were 100%, 70.2°C, and 110.5 min, respectively. The optimal predicted contents for total phenolics (9.03 mg Gallic Acid Equivalent (GAE)/g DW) and carotenoid (8.74 mg/g DW) values in the extracts were agreed with the experimental values obtained with optimum extraction conditions for each response, and also they possess significantly higher total antioxidant capacity.