| Tea,as a traditional beverage originating in China,is deeply loved by consumers because of its unique flavor and health effects.In tea industry,there are many kinds of tea due to the difference of climate and topography,tea varieties and processing methods,adding difficulties to the detection and identification of tea quality.At present,the Discrimination of tea in the market mainly depends on the professional evaluation of tea.However,manual evaluation often depends on the accumulation of experience,which can not meet the needs of the market.Therefore,it is imperative to study the quality of tea and establish a method to quickly discriminate the grade of tea.In addition,the protection of nerve by tea drinking is widely respected,but the mechanism is not clear.Therefore,based on the current research,the quality of tea and the protective mechanism of tea on nerve cells were studied by fluorescence spectroscopy.In this study,46 kinds of tea were used as raw materials for three-dimensional fluorescence detection.The three-dimensional detection spectra of 19 common compounds in tea were studied,and the three-dimensional fluorescence components of tea were analyzed.Three-dimensional fluorescence fingerprint of tea was improved and the positions and fluorescence characteristic peaks of catechins,alkaloids and other compounds in the fluorescence spectrum were determined.Bovine serum albumin(BSA)can specifically bind to catechin and produce fluorescence quenching.The fluorescence experiments were carried out with 8 different levels of Dian-Hong and the experimental results were processed.Principal component analysis(PCA)and orthogonal least squares discriminant analysis(OPLS-DA)were used to analyze the classification trend of Dian-Hong tea in different grades and to establish a rapid fluorescence detection method for distinguishing different teas.In the model prediction,PCA prediction ability Q2 = 0.995,OPLS-DA prediction ability Q2 = 0.527,and OPLS-DA model validation parameters Q2 =-0.119,proved that the fluorescence quenching method in different levels of Dian-Hong identification have good accuracy.In the study of the neuroprotective effects of tea,neutrophil gelatinase-associated lipocalin(NGAL)is thought to directly damage nerve cells or indirectly induce neuronal apoptosis,while NGAL inhibitors can alleviate the symptoms.The interaction between catechin and NGAL was studied by fluorescence spectroscopy and molecular simulation.In the fluorescence quenching experiment,it was found that the fluorescence intensity ofNGAL protein was changed regularly by adding tea soup or catechin.The thermodynamic analysis of fluorescence experiments showed that in the presence of Fe3+,the more catechol the ester catechin had,the stronger the binding capacity with NGAL was.A natural epicatechin 3-o-caffeic acid ester(ECC)isolated from green tea was found to have the strongest binding ability to NGAL(K d = 15.21 n M)in the presence of Fe3 +.Nerve cell injury experiments demonstrated that catechin protects nerve cells in two injury models(H2O2 and A?1-42 induced SH-SY5 Y cells injury).On the basis of nerve cell experiment,the changes of NGAL level and the effect of catechin on the cell and NGAL protein were measured.In this paper,based on the fluorescence spectrum technology,the three-dimensional fluorescence fingerprint of tea was studied from the fluorescence characteristics of the compound.A rapid fluorescence detection method for different grades of Dian-Hong was established by using BSA as fluorescent carrier.In addition,based on the fluorescence quenching experiment,the mechanism of catechin protecting nerve cells through NGAL protein was studied and discussed,which laid the foundation for further study on the protective function of tea drinking on nerve. |
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