Effect Of Simulated Digestion In Vitro On Phenolic Compounds And The Antioxidant Activity Of Pickled Mustard Leaves

Pickled mustard is rich in polyphenols,flavonoids,anthocyanins,tannins,which can effectively prevent diabetes,obesity,hypertension and other diseases.Whether phenolics can be fully released in the human body and realize their various functions is closely related to their digestion,absorption and metabolism.Therefore,it is particularly important to evaluate the changes of phenolics after digestion.In this study,pickled mustard leaves were used as raw materials to study the changes of phenolic components,antioxidant activities and the activities of enzyme related to metabolic syndrome of pickled mustard leaves and its ethanol extracts after digestion,the protective effects of vegetable oil on phenolic substances,and the effects of different digestion methods on antioxidant performance were studied by simulated digestion in vitro.The main research contents and conclusions were shown as follows:(1)The effects of simulated digestion in vitro on the phenolic compounds and antioxidant activities of pickled mustard leaves(PM)and its ethanol extracts(PM-E)were studied.The results showed that the contents of total phenol,flavonoids,anthocyanins and tannins were significantly increased in PM and PM-E after in vitro digestion,2,2’-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)diammonium salt(ABTS),2,2-diphenyl-1-picrylhydrazyl(DPPH)free radical scavenging ability and iron reducing ability(FRAP)were increased,the antioxidant ability was enhanced,and PM>PM-E.The correlation analysis showed that total phenol,flavonoids,anthocyanins and tannins were the key factors affecting the change of the antioxidant activities of PM and PM-E.HPLC-MS analysis showed that nine phenolic compounds including o-coumaric acid,p-coumaric acid,p-hydroxybenzoic acid,ferulic acid,4-hydroxyl cinnamaldehyde,gallic acid,quercetin,kaempferol and isorhamnetin were identified.After in vitro digestion,the contents of o-coumaric acid,p-hydroxybenzoic acid and gallic acid were significantly increased.(2)The effects of simulated digestion in vitro on the antioxidant activities of phenolic compounds in different forms from pickled mustard leaves and its ethanol extracts were studied.The results showed that the contents of total phenol and flavonoids were significantly increased in free phenolics from PM and PM-E after digestion,ABTS,DPPH radical scavenging ability and FRAP were increased,and the antioxidant activity was enhanced.The contents of total phenol and flavonoids,ABTS,DPPH free radical scavenging ability and FRAP were overall upward trend in conjugated and bound phenolics after digestion,and the antioxidant capacity was enhanced.The correlation analysis showed that the contents of total phenol and flavonoids were the main factors affecting the change of the antioxidant activities of phenolic compounds in different forms from PM and PM-E after digestion in vitro.(3)The effects of simulated digestion in vitro on the activity of enzymes related to the metabolic syndrome of pickled mustard leaves and its ethanol extracts were studied.The results showed that the bioaccessibility of total phenol and flavonoids increased in PM and PM-E after digestion.The undigested samples of PM and PM-E inhibited α-amylase and α-glucosidase,PM-E>PM,the inhibitory effect of digested samples on α-amylase and α-glucosidase was significantly enhanced.PM and PM-E had no inhibitory effect on lipase before and after digestion.The correlation analysis showed that total phenol,flavonoids and tannin were the key factors affecting the inhibition of PM and PM-E on α-amylase and α-glucosidase.(4)The combination of pickled mustard leaves with vegetable oil(O)were studied in order to evaluate the protection of vegetable oil on the phenolic compounds submitted to in vitro digestion conditions.The results showed that the contents of total phenol,flavonoids,anthocyanins and tannins were significantly increased in PM+5%O and PM+10%O after digestion,and the antioxidant activity was enhanced.Compared with PM,the contents of total phenol,anthocyanins and tannins were higher after adding vegetable oil,the antioxidant capacity was enhanced.The antioxidant capacity was stronger with the increase of vegetable oil.(5)The effects of five different simulated digestion in vitro methods(D1-D5)on the antioxidant activities of pickled mustard leaves were studied.The results showed that the contents of total phenol,flavonoids,anthocyanins and tannins were increased in PM-D1 after digestion,and the antioxidant ability was enhanced.The contents of total phenol,flavonoids and tannins were increased in PM-D2,and the antioxidant ability was enhanced.The contents of total phenol,flavonoids and tannins were increased in PM-D3,and the antioxidant ability was decreased.The contents of total phenol,flavonoids and anthocyanins were decreased in PM-D4,the content of tannin had no significant difference,and the antioxidant activity was decreased.The contents of total phenol and tannins were increased in PM-D5,and the contents of flavonoids and anthocyanins were decreased,ABTS free radical scavenging ability was decreased,DPPH free radical scavenging ability was increased,while FRAP showed no significant difference,and the antioxidant activity was not obvious.