Recovery Of Walnut Flavonoid In Peeling Wastewater Of Walnut Kernel And Its Anti-oxidative Activity

Walnut polyphenols were rich in walnut kernel and walnut pellicle most.But walnut pellicle needed to be removed in the process of walnut milk production.Currently,lye de-pellicle was the widest method in walnut de-pellicle.Studied have shown that walnut kernel were soaked and de-pellicle by lye could result in the decrease of polyphenols and flavonoids.Besides,the content of chemical oxygen demand(COD)was far beyond the secondary emission standards of China.This study with soaking and lye from production process of walnut milk as raw material and separation and purification of walnut polyphenols by macroporous resin.Moreover,we investigated the antioxidant activity and chemical composition of polyphenols by LC-MS.Besides,the interaction of polyphenols on antioxidant and polyphenols and protease were analyzed.The main contents and results were as follows:1.Separation and purification of walnut polyphenols from walnut de-pellicle wastewater by macroporous resin.Flavonoids as index,five macroporous resins were selected to compare their adsorption and desorption performances for walnut polyphenol.The best performance resin was AB-8 whose dynamic adsorption test was researched and the best process parameters were determined.The purity of polyphenols and flavonoids were 73.26%and 61.35%,respectively.2.Identification of walnut polyphenols by LC-MS and antioxidant activity in vitro.There were 8 walnut polyphenols from walnut de-pellicle wastewater by LC-MS.(-)-Epicatechin is the compound with the highest content(21.24%),quercetin(16.40%)and gallic acid(13.45%)followed.Besides,the experiments of antioxidant activity revealed that IC50 values of walnut polyphenols on DPPH radical,superoxide anion and hydroxyl radical were 33.71 μg/mL,0.32 mg/mL 和 0.472 mg/mL,respectively.Moreover,walnut polyphrenols had strong reducing ability and dose-dependent.3.Interaction of walnut polyphenols on antioxidant activity.Through the studies found that synergy interaction among several polyphenols on DPPH radical included quecetin and epicatechin,quercetin and gallic acid,gallic acid and epicatechin.The synergy interaction of quecetin and epicatechin was more obvious.Antagonistic interaction among several polyphenols on DPPH radical included epicatechin and salidroside,epicatechin and ferulic acid,gallic acid and salidroside,gallic acid and ferulic acid,salidroside and ferulic acid,salidroside and quercetin,ferulic acid and quercetin.Antagonistic interaction of salidroside and ferulic acid was more obvious.4.Interaction of walnut polyphenol and protease.Interaction of gallic acid and trypsin were analyzed by spectrum,enzymatic and molecular model.The results revealed that there was obvious quenching effect between gallic acid and trypsin and quenching mechanism was static quenching.The non-radiative energy transfer occurred between gallic acid and trypsin.Besides,thermodynamic analysis demonstrated that Van der Waals force,hydrophobic,hydrogen bonds and electrostatic interactions were involved in the binding process.Enzymatic experiments revealed that gallic acid exhibit obvious inhibit effect on trypsin and the IC50 values was 3.9×10-6 mol/L.Molecular duck results agreed well with results of previous experiments and offered more specific evidence for explaining the interaction mechanism.