Extraction and characterization of phenolic compounds of jujube (Ziziphus jujuba) by innovative techniques.

This study aimed to optimize the extraction of phenolic compounds from jujube by conventional (CE), ultrasound (UAE), and microwave-assisted (MAE) extractions using the response surface methodology, compare the extraction techniques and determine some bioactive properties of the phenolic extracts. In addition to time and solvent concentration, temperature for CE, sonicator power and duty cycle for UAE and microwave power for MAE were optimized. The optimum point to recover phenolic extract from jujube by CE was 1410 min for extraction time, 80℃ for extraction temperature, and 40% for methanol concentration. The optimal extraction conditions for phenolic compounds of jujube by MAE were determined to be as follows: 300 W microwave power, 127 s extraction time, and 43% methanol concentration. The optimum values of jujube extract by UAE are 20 min, 10:7, 130 W, and 40% for extraction time, duty cycle, sonicator power, and methanol concentration, respectively. It was found that the total phenolic compounds (TPC) in CE, MAE, and UAE extracts were 2.7552mgGAE/g, 3.3455mgGAE/g, and 1.9416mgGAE/g, respectively. The highest TPC was in MAE as 3.3455mgGAE/g, the highest TFC was in UAE as 1671.1111mgQE/kg, the highest ascorbic acid was in UAE as 2.2489 mg/100 g, the highest TEAC was found in MAE as 3449.79mgTE/kg, and the highest FRAP was found in CE as 670mgTE/kg. Different amounts of catechin, succinic acid, cyanidin chloride, rosmarinic acid, salicylic acid, routine, oxalic acid, and quercetin dihydrate were detected in the extracts.