Extraction Process of Polyphenols from Soybean (Glycine max L.) Sprouts: Optimization and Evaluation of Antioxidant Activity

Abstract

This research aimed to optimize the total polyphenol content (TPC) extracted from soybean sprout powder under different experimental parameters, including ethanol concentration (60–100% v/v), extraction temperature (40–80 °C), extraction time (15–150 min), material:solvent ratio (1:4–1:10 g/mL), the number extraction cycles (1, 2 and 3 times), the age of sprout (0–7 days), and the used part of the sprout (cotyledon, hypocotyl, or radicle). The obtained results were used in response surface methodology, in combination with a central composite design, to model the total polyphenol content (TPC) with respect to three variables, including ethanol concentration, extraction temperature, and material:solvent ratio. The experimental conditions for optimal recovery of TPC consisted of ethanol concentration of 88% (v/v), extraction temperature of 59 °C, material:solvent ratio of 1:6.5 g/mL, extraction time of 60 min, and 2 cycles of maceration. In addition, for maximal TPC, the sprout should undergo the germination of 5 days and the radicle fraction should be used. Based on the suggested optimum conditions, the obtained and verified TPC was 19.801 mg genistein (GE)/g dry weight (d.w.). The obtained dried extract also exhibited low antioxidant activity.