The optimal process for litchi pericarp procyanidin extraction using deep eutectic solvents(DESs)was established to provide technical support for the efficient green preparation of litchi pericarp procyanidins.Litchi pericarp procyanidins were extracted using four DES types and 70%(V/V)ethanol to investigate and compare the extraction efficiency and the chemical composition and antioxidant activity(oxygen radical absorbance capacity)of the obtained procyanidins.HPLC-DAD analysis revealed that two procyanidin compounds(procyanidin A2 and B1)and three flavonoids(rutin,epicatechin,and kaempferol-3-O-rutinoside)were present in the extracts acquired using the four DESs and ethanol.Choline chloride-1,3-butanediol was the best extractive solvent.Furthermore,single factor tests and orthogonal optimization suggested that the optimum extraction conditions for choline chloride-1,3-butanediol are as follows:a liquid ratio of 1∶20(g/mL),a solvent molar ratio of 1∶4,a solvent water content of 50%(V/V),an extraction temperature of 60℃,and an extraction time of 90 min.Under these conditions,the total procyanidin content reached 5.07 mg PE/mL,which is 1.4-fold that extracted using 70%ethanol.The oxygen radical absorbance capacity values and the IC50 values of the DPPH and ABTS free radicals of the finished choline chloride-1,3-butanediol-extracted extract were 5 496.25 μmol TE/mL,27.35 μg PE/mL,and 23.82 μg PE/mL,respectively.In short,these results indicate that DESs exert significant advantages in the extraction of litchi pericarp procyanidins.
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