Response Surface Methodology for Optimization of Extracting Total Flavonoids from Maca Leaves and Antioxidant Evaluation

Response surface methodology(RSM) was employed to optimize the extraction conditions of total flavonoids from Maca leaves collected from Lijiang(Yunnan province). Based on single-factor tests, Box-Benhnken center composite experiment was carried out with three factors, including alcohol concentration, extraction temperature, solid-to-solvent ratio. RSM was used to determine the effect of prime factors on the yield of flavonoids. Besides, the antioxidant activity in vitro of flavonoids from maca leaves was evaluated. Results showed that the optimum extraction conditions by RSM were ethanol concentration 65%, extraction temperature 64 ℃, and solid-to-liquid ratio 29:1(mL/g). Under these conditions, the extraction yield of total flavonoids was(2.49±0.02) %, which was close to the measured value. Thus, the fitted quadratic regression model was valid. The IC50 of the obtained total flavonoids against hydroxyl, superoxide anion and DPPH radicals were 0.605, 0.425 mg/mL and 0.165 mg/mL, respectively. The scavenging impact of the three radicals was more effective than that of 2,6-di-tert-butyl-4-methyl phenol(BHT) at the same concentration, but lower than vitamin C.