Optimization of ultrasound-assisted extraction of indigo and indirubin from Isatis indigotica Fort. and their antioxidant capacities
2017
Guihong Zhao, Shaanxi Normal University, Xi'an, China | Tao Li, Shaanxi Normal University, Xi'an, China | Xinyun Qu, Shaanxi Normal University, Xi'an, China | Nini Zhang, Shaanxi Normal University, Xi'an, China | Miao Lu, Shaanxi Normal University, Xi'an, China | Jing Wang, Shaanxi Normal University, Xi'an, China
An effective method for the ultrasound-assisted extraction of indigo and indirubin from Isatis indigotica Fort. was established and their antioxidant activities were investigated. Response surface methodology based on a three-level, four-factor Box Behnken design was used to optimize the extraction conditions. Analysis of variance showed that the quadratic model was significant for the extraction of indigo and indirubin (112.72% plus-minus 1.65% and 116.42% plus-minus 1.27%, respectively) under the optimal conditions (methanol concentration, 80%; extraction time, 25 min; ratio of solid to liquid, 1:34 g/mL; and extraction temperature, 41 degree Celsius) and was in good agreement with the predicted value. Moreover, evaluation of the antioxidant activities suggested that indigo and indirubin presented better scavenging effects on 1,1-diphenyl-2-picrylhydrazyl free radical and superoxide radical than the extract and the extract revealed certain antioxidant activities in hydroxyl radical scavenging and reducing power, and indigo and indirubin could be used as natural antioxidants in the food or medicine industry.
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