Optimization of microwave-assisted extraction of total flavonoids from china-hemp leaves and evaluation of its antioxidant activities

Abstract

In order to obtain higher extraction yield and basic technological information for total flavonoids (TF) in China-hemp leaves, response surface methodology (RSM) was employed to optimize microwave assisted extraction (MAE) process of TF from China-hemp leaves. RSM based on a three-level, four-variable central Box-Behnken design (BBD), was evaluated to obtain the best possible combination of ethanol concentration, the ratio of liquid, extraction time and temperature for maximum TF extraction. The experimental results indicated that the optimum extraction conditions were ethanol concentration of 70%, solvent-to-solid ratio of 32 mL/g, extraction time of 25 min and extraction temperature of 70 °C. Under these conditions, the yields were 3.04 ± 0.62%, which is in close agreement with the value predicted by the model 3.06%. Moreover, the antioxidant activity of ethanol extracts were evaluated, and the results showed that these extracts have different reducing power and scavenging effect for DPPH and ABTS radical.