Optimization of ultrasound-assisted extraction of total phenolic contents and antioxidant activity using response surface methodology from jujube leaves (Ziziphus jujuba) and evaluation of anticholinesterase inhibitory activity

An ultrasound-assisted procedure for the extraction of phenolics (TPC) and antioxidant activity (AA) from jujube leaves have been investigated using response surface methodology (RSM). The Box–Behnken design was used to investigate the effects of three independent variables, solvent concentration (methanol/water; 40–100%), ultrasound-intensity (20–100%), and extraction time (3–15 min) on the responses. The optimal extraction conditions were 64.20% methanol, 73.60% ultrasound intensity, and 13.27 min. Under optimal conditions, the corresponding experimental values for TPC and AA were 6098.14 mg GAE/100 g DM and 4010.63 mg AAE/100 g DM. The experimental values were in close agreement with those predicted values within a 99% confidence level, thus indicating the suitability of the model and the success of RSM in optimizing the ultrasound assisted extraction of TPC and AA of jujube leaves. The results showed that optimized jujube leaves extract exhibited inhibitory effects on both acetylcholinesterase and butyrylcholinesterase with IC 50 of 62.30 ± 2.54 and 147.00 ± 2.31 µg/mL, respectively.