Oxidation Change Of Coix Seed Oil And Its Effect On Mice Body Damage

Coix seed was abundant with active oil,which composed of triglycerides,coixenolide,fatty acids and derivatives.But high-unsaturated fatty acids in the oils were prone to be hydrolyzed or oxidized,thus make the quality deterioration and induced hazards substance,this phenomenon becomes a crucial problem in the development and utilization of Coix seed resources.Therefore,the nuclear magnetic resonance?NMR?technology and the gas chromatography-mass spectrometry?GC-MS?detection methods will applied to monitor the oxidation process of the oils at different storage times,finally,the mice model will build for safety evaluation on the oxidized oils hazards.The main results are as follows:?1?The oxidation degree changes of Coix seed oil at room temperature and 60°C was obtained by ¹H NMR technique,principal component analysis,hierarchical clustering analysis,and partial least squares discriminant analysis.The results showed that the content of linoleic acid,oleic acid,and saturated fatty acid in fresh Coix seed oil was 34.20%,50.22%,and 15.58%,respectively.While storage at room temperature for 135 days,the ¹H NMR signal strength for the primary and secondary oxidation products was very weak,and the content of linoleic acid,oleic acid,and saturated fatty acid decreased by 16.46%,1.83%,and 30.23%,respectively.When the oxidation process of Coix seed oil was accelerated for 42 days,the signal's strength of olefinic,bis-allylic and allylic protons was reduced obviously.And the signal strength of oils secondary oxidation products gradually increased since the 18th day,indicating that the oxidation of oil has been accelerated.In the range of oxidation reaction from the start to the termination,the linoleic acid content decreased by 71.99%,oleic acid increased by 7.33%,but the saturated fatty acid content increased by 1.34 times.It shows that the fatty acids component of the oil changes differently as the oxidation temperatures,and the degrees of oxidation satisfied the orders:PUFA>MUSA>SFA,and proved that the accelerated oxidation can really induced quality deterioration of the oils when compared to the room temperature conditions.The principal component analysis?PCA?and hierarchical clustering analysis?HCA?can both separate the oil samples under different oxidative conditions effectively.The PLS-DA model can identify different oxidation conditions and pathways of the Coix seed oil under two different oxidation temperatures.It can be seen that the constructed qualitative analysis model that combined with the¹H NMR fingerprint and multivariate statistical analysis method can reflect the conditions of oil oxidation more accurately and comprehensively,and also can classify and identify oils correctly,this gives a reference of quality control and evaluation on Coix seed oil.?2?The dynamic content changes of flavor compounds during the oxidation period of Coix seed oil were analyzed by solid phase microextraction-gas chromatography-mass spectrometry and electronic nose technique.The results showed that the characteristic volatile flavor compounds during the period of Coix seed oil accelerated oxidation were mainly composed of aldehydes,ketones and alcohols.In the fresh Coix seed oil,the key flavor compounds that contribution with a relative odor activity value?ROAV?larger than 1 was ordered as follows,?E?-2-nonenal,?E,E?-2,4-decadienal,?E?-2-decenal,?E,Z?-2,6-nonadienal,1-octen-3-one,decanal,and these gives the oil grassy,oily,and watermelon smell.With the increase of the oxidation time,and the deterioration of the oil quality was serious.The relative content of aldehydes was 73.815%when accelerated at 60?for 30 days,and the relative content of small molecules of aldehydes,acids and alcohols was increased as compared with fresh oil.The new added key flavor compounds after the accelerated oxidation of coix seed oil were nonanal,octanal,hexanal,?E?-2-octenal,these gives the oil a rancid odor.The basic characteristic compounds of fresh Coix seed oil oxidation were?E?-2-nonenal,?E,E?-2,4-decadienal,etc.And the small molecules such as nonanal,octanal,hexanal were the characteristic volatile compounds after accelerated oxidation of Coix seed oil.The electronic nose LDA results well distinguished the difference of the fresh and oxidized oil and related volatile flavor compounds that generated from the oxidation initial to final.It can be observed that the characteristics odors of the oil are significantly different under different oxidation stages.Meanwhile,the discriminant function?DFA?methods can well predict the storage period of unknown samples,and the correctness rate is the highest,reaching 94.29%,which is better than the Euclidean distance,correlation and Mahalanobis distance.?3?The fatty acid composition,malondialdehyde,chroma,the content of two conjugated olefin(K₂₃₂,K₂₇₀)and other indicators were used to evaluate the nutrient quality changes of the fresh Coix seed oil before and after 30d accelerated oxidation at60°C.And the mice model?control group,fresh oil group,dose groups with low,medium and high content of oxidized oil,gavage 30 days?was set to evaluate the impact of oxidized hazards on mice serum biochemical index,oxidative stress and liver tissue damage.The results showed that compared with fresh Coix seed oil,the polyunsaturated fatty acid content of oxidized oil was only 8.15%,linoleic acid decreased by 75.3%?P<0.01?,POV and AV increased?P<0.01?,and MDA content increased by 16.24 mg/kg?P<0.01?.Moreover,ingestion of oxidized oil causes intestinal flatulence in mice and slow weight gain.The activities of ALT and AST in each dose group were higher than those in the fresh oil group,while the activities of liver antioxidant enzymes?GSH-Px,SOD,CAT?were decreased?P<0.05,P<0.01?.In addition,oxidized oil treatment induced the content increase of oxidative stress biomarkers MDA?P<0.05,P<0.01?and 8-OHdG?8-hydroxy-2'-deoxyguanosine??P<0.01?.Histopathological section revealed that the liver cells of mice showed lesions such as fatty vesicles and inflammatory cell infiltration.The mice model indicated that the quality of the Coix seed oil was turn worse after oxidation and caused toxic side effect on the mice body,which induced serious oxidative stress and liver pathological damage.