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

Abstract: 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. [Copyright &y& Elsevier]