Abstract:A highly efficient and environmentally friendly method for the preparation of high-value natural antioxidant phloretin was described in this work. Naringin dihydrochalcone was prepared from naringin which is a kind of natural citrus extract by one pot hydrogenation, and then was hydrolyzed by α-rhamnosidase and cellulase to product phloretin. The process conditions including pH, temperature and substrate to enzyme ratio of α-rhamnosidase and cellulase were optimized by single factor and orthogonal experiments. The antioxidant activity of phloretin, trilobin, naringin dihydrochalcone and naringin were also studied. The results showed that the optimum conditions of α-rhamnosidase were as follow: temperature of 60 ℃, pH of 4.0, and the substrate to enzyme ratio of 0.6:1. The optimum conditions of cellulase were as follow: temperature of 45 ℃, pH of 5.5, and the substrate to enzyme ratio of 0.3:1. Under these optimum conditions, the conversion of phloretin was 96.1%, which increased by 10.53% compared to the original method. The orders of antioxidant activity were as follows: the DPPH free radical scavenging capacity of phloretin (0.18±1.45) > trilobatin (0.3±1.63) > naringin dihydrochalcone (0.95±1.24) > naringin (8±1.97), the reduced iron ion capacity of phloretin (7.1±0.68) > trilobatin (2.51±0.75) > naringin dihydrochalcone (2.05±0.58) > naringin (0.11±0.92). The new preparation method of phloretin was mild, short-cycle, high-conversion and was easy to scale up. Phloretin produced by this method had a good antioxidant activity. This work will be helpful to the enlarge production and application of phloretin.
