Extraction optimization by response surface methodology, purification and principal antioxidant metabolites of red pigments extracted from bayberry (Myrica rubra) pomace

The optimized extraction conditions of red pigments (RP) from bayberry (Myrica rubra) pomace obtained with response surface methodology were extraction pH, time, temperature, liquid/solid ratio as 1.4, 4.2 h, 56.1 °C and 12.6/1 ml/g, respectively. The RP were then purified by the macroporous resin, which indicated the resin LX-68 showed the maximum refined efficiency among the tested resins. Further solvent partition of the RP yielded ethyl acetate, n-butanol and water layers, in which the first fraction showed the strongest DPPH and hydroxyl radical scavenging activities with IC50 values of 2.13 μg/ml and 0.57 mg/ml, respectively, which were higher than those of BHA and mannitol used as a positive control. Following activity-oriented separation, (−)-epicatechin and procyanidin B2 were isolated from the ethyl acetate layer and were found to have excellent DPPH free radical scavenging activities with IC50 values of 2.87 and 2.06 μg/ml, respectively.