Extraction of Antioxidants from Aloe vera Leaf Gel: a Response Surface Methodology Study

Extraction of antioxidants from aloe gel powder with water-ethanol solvents was studied using response surface methodology. The independent variables were solvent composition, temperature, extraction time, and the liquid-to-solid (L/S) ratio. The concentrations of potentially antioxidant compounds (aloin A and B, aloesin, total phenolics, and total carbohydrates) and a few indicators of antioxidant capacity (DPPH, FRAP, CUPRAC) served as the response functions. It was found that aloe gel contains both phenolic and non-phenolic antioxidants, and it was supposed that the phenolic fraction consists almost exclusively of chromones and anthrones. Different approaches to the optimization of extraction procedures are discussed, and here, the maximum recovery yield of antioxidants is achieved with 34 % ethanol at 60 A degrees D and a L/S ratio of 46 in 1 h. The use of 90 % ethanol results in a higher antioxidant capacity of the product, but also results in a much lower extraction yield, decreasing the overall productivity of the process.