Abstract:This study aimed to explore the extraction technique of gallic acid from Acer ginnala leaves to determine its optimal extraction process.The extraction process was optimized by response surface methodology by the tannase-coupled ultrasound-microwave synergistic extraction method with 60% ethanol solution as the extraction solvent and the yield of gallic acid as the evaluation index based on the six single factor tests，including extraction time，tannase addition，microwave power，extraction temperature，solid-to-liquid ratio，and pH value.Gallic acid was further purified using the ion exchange resin recrystallization method.The in vitro antioxidant activities of gallic acid and ascorbic acid（VC）were evaluated with DPPH and ABTS+ radical scavenging rates as indicators.The results showed that the optimal extraction process parameters for gallic acid were as follows: extraction time of 40 min，tannase addition of 4.3%，solid-to-liquid ratio of 1∶60（g/mL），microwave power of 520 W，extraction temperature of 60 ℃，and pH value of 7.Under these conditions，the yield of gallic acid was（26.25±0.41）%，which was close to the theoretically predicted value of 26.64%.After purification，the purity of gallic acid reached over 90%.In DPPH and ABTS+ free radical scavenging experiments，the scavenging rate of gallic acid in Acer ginnala leaves was higher than that of VC.The results have shown that the tannase-coupled ultrasound -microwave synergistic extraction method can improve the yield of gallic acid in Acer ginnala leaves which has strong antioxidant capacity.