Microwave and enzyme co-assisted extraction of anthocyanins from Purple-heart Radish: Process optimization, composition analysis and antioxidant activity

Abstract

Purple-heart Radish named “Xinlinmei” is rich in anthocyanins by specific cultivation. In this work, a novel method for synergistic extraction of anthocyanins from Purple-heart Radish was developed by combining microwave-assisted extraction (MAE) with enzyme-assisted extraction (EAE). Integration of MAE and EAE was optimized by screening various enzymes and combination approaches, followed by investigation of process parameters with single-factor experiments and response surface methodology (RSM). The optimized conditions by RSM were as follow: 25.0 g/100 g cellulase dosage, 60 mL/100 mL ethanol concentration, pH 4.0, 50 °C temperature, 7.15 min extraction time, 80 mesh particle size and 60:1 mL/g liquid-to-material ratio, yielding a maximum response predicted and experimental values of 6.292 and 6.125 ± 0.034 mg/g respectively. Based on the synergistic effect, MAE-EAE achieved higher extraction efficiency compared to the other extraction methods such as MAE, UAE and EAE etc. By means of HPLC-Q-Orbitrap/MS and HPLC, 11 anthocyanins extracted were identified and quantified as pelargonins with different glucosides, exhibiting quite homologous fragmentation pattern, biometabolic products and satisfactory yield. The antioxidation capacity of the extracted and purified products was evaluated by DPPH, ABTS and anti-lipid peroxidant assays, suggesting that the anthocyanins purified by the macroporous resin had stronger antioxidant activity. This study provided an efficient and promising approach to improve extraction of the anthocyanins from Purple-heart Radish, and a new source of pelargonins as a powerful antioxidant to be developed.