Identification And Antioxidant Interaction Of Endogenous Phenolic Compounds In Tea Seed Oil

Tea seed oil,obtained by pressing the seeds of Camellia Sinensis O.Ktze.is rich in unsaturated fatty acids and various beneficial components,and is resistant to storage and has high nutritional value.It had been demonstrated that the storage resistance of tea seed oil was directly related to its endogenous phenolic compounds,which were complex and diverse in composition,and their mechanism of action on the oxidative stability of the oil was still unknow.In this thesis,the endogenous phenolic compounds of tea seed oil were studied,and the best extraction process for the endogenous phenolic compounds was determined through the screening of extraction solvents and the optimization of alkaline digestion process.The composition of endogenous phenolic compounds in tea seed oil was analyzed by UPLC-MS/MS.On this basis,the phenolic compounds with high content and theoretical antioxidant capacity were selected for antioxidant interaction studies,and the effects of the interactions on the oxidation process of the oil were futher analyzed.The main results of the study were as follows.(1)Fuding Dabai tea seeds were used as raw materials,and the tea seed oil was obtained from the crushed tea seeds after dehulling and pressing.The extraction of endogenous phenolic compounds in tea seed oil was carried out by alkali digestion method,and the extraction efficiency of different polar organic solvents was compared with the total phenolic content and antioxidant capacity as evaluation indexes,and ethyl acetate was determined as the extraction solvent.The extraction process was further optimized to obtain the best extraction process:NaOH concentration of 2 mol/L,temperature of 45℃,time of 5 h,and material-liquid ratio of 1:15.The phenolic content of tea seed oil obtained under this condition was 91.37±1.83 μg/g.The endogenous phenolic compounds of tea seeds were identified by UPLC-MS/MS.A total of 22 phenolic compounds were identified,among which 15 phenolic compounds were found in tea seed oil for the first time,including quercetin-3 β-D-glucoside,catechol,esculetin,gallic acid 4-O-glucoside,hesperetin,quercetin 3-O-arabinoside,cyanidin 3-O-galactoside,glycitein,gallic acid 3-O-gallate,p-coumaroyl tartaric acid,caffeoyl tartaric acid,protocatechuic acid 4-O-glucoside,feruloyl tartaric acid,4-hydroxybenzoic acid 4-O-glucoside(2)The relative contents of endogenous phenolic compounds in tea seed oil and their theoretical antioxidant values were used as evaluation indexes,and quercetin,quercetin 3-O-arabinoside,rhamnetin,cyanidin 3-O-galactoside,caffeoyl tartaric acid,esculetin and gentisic acid were selected for antioxidant interaction studies.The types of endogenous phenolic compound interactions in tea seed oil were analyzed by DPPH-scavenging and Rancimat methods using ethanol and lard as the study media.The results showed that the different concentration of the compounds affected the antioxidant interaction type of the binary mixture,and their antioxidant synergistic effect was optimal at 0.4 × IC50,and some of the synergistic components showed a dose-dependent relationship.Meanwhile,the interaction types of phenolic compounds were influenced by the medium of action,and the antioxidant effect of lipid-soluble phenolic compounds was more obvious in non-polar medium.The synergistic effects of quercetin+esculetin,caffeoyl tartaric acid+gentisic acid,caffeoyl tartaric acid+esculetin and esculetin+gentisic acid were found in both media,with the most pronounced synergistic effect after the combination of esculetin+gentisic acid(CI=0.435,S%=1.82).(3)Rancimat,Schaal,EPR and GC-MS were used to monitor the induction time,oxidation products,free radicals and volatile components during lipid oxidation to investigate the effect of synergistic phenolic compounds on the lipid oxidation process.The results showed that phenolic compounds could act as hydrogen donors and reduce the formation of lipid radicals.The delaying effect of the binary phenolic mixture on the oxidation process of oils was significantly stronger than that of the monomeric phenolic compounds.Esculetin+gentisic acid played an important role in the early stage of oxidation,and the addition of gentisic acid inhibited the electron-absorbing group of 1,2-pyrone in the structure of,and the increased hydrogen-donating capacity enabled this component to effectively block the chain reaction.Meanwhile,quercetin+esculetin played an important synergistic role in inhibiting the degradation of hydrogen peroxide and the oxidation of linoleic acid.