| Allergic reaction is an Ig E-mediated hypersensitivity.Its clinical manifestations of eczema,rhinitis or asthma and other allergic diseases.In serious cases can cause collapse and shock,and even life-threatening.In recent years,the number of people suffering from allergic diseases has increased rapidly around the world,seriously affecting people's normal lives.As the main treatment method at present,drug therapy has a quick effect,but it has great side effects and is easy to produce drug resistance.However,it is particuarly important to develop foodborne natural products with anti-allergic effects to make up for the shortcoming of traditional drug.Objective: The purpose of this study is to extract cashew oligopeptide from cashew protein and explore its inhibitory effect on allergic reaction,so as to broaden the research approach for the treatment of allergic reaction and provide experimental basis for the development and application of cashew.Methods: Cashew protein was extracted from cashew by alkali-solution and acid-isolation,and identified by UV and IR spectra.Cashew crude oligopeptide was obtained by enzymatic hydrolysis,and the most suitable enzyme was screened by molecular weight distribution,degree of hydrolysis(DH)and polypeptide yield(TCA-YSP).The effects of reaction time,reaction temperature,substrate p H,substrate concentration and enzyme concentration on TCA-YSP were investigated,and the enzymatic hydrolysis conditions were optimized by Plackett Burman(PB)test and response surface method.Cashew crude oligopeptide was purified by ultrafiltration,dextran gel chromatography and semi-preparative liquid chromatography.The purity of the oligopeptide was determined by analytical liquid chromatography and SDS-PAGE,and the structure of the sample was identified by ultraviolet spectrum,infrared spectrum,scanning electron microscope and mass spectrometry.The model of mast cell allergy induced by DNP-BSA was established,and the degree of mast cell degranulation and the expression of tumor necrosis factor-?(TNF-?)were measured to explore the anti-allergic effect of cashew oligopeptide.Results:(1)preparation of cashew oligopeptide.Cashew protein was extracted by alkali-solution and acid-isolation with a purity of 91.94 ± 0.55%.According to the results of molecular weight distribution,more small molecular weight peptides could be obtained by selecting alkaline protease than other proteases,and the DH and TCA-YSP of the hydrolysate were 17.06 ± 1.52% and 26.28 ± 0.13%,which were significantly higher than those of other proteases.Therefore,alkaline protease is the most suitable protease for the preparation of cashew oligopeptides.The optimum conditions of enzymatic hydrolysis were obtained as follows: time 5 h,temperature42.5?,p H 11.5,substrate concentration 40 g/L and enzyme concentration 8%.After multi-step separation and purification,the F1-a-1 component was obtained,and its hyaluronidase inhibition rate was 95.53 ± 2.75%.The results of UV and IR spectra showed that the F1-a-1 component was composed of a peptide containing ? helix,and the cashew oligopeptide with molecular weight 960.5 Da of Ile-Ile-Ala-Ile-Pro-Ala-GIy-Val-Ala-His(IIAIPAGVAH),was determined by mass spectrometry.(2)The antiallergic effect of cashew oligopeptide.Compared with the model group,200 ?g/m L and 500 ?g/m L cashew oligopeptides significantly inhibited the release of histamine and ?-aminohexosidase(?-HEX),the degree of phosphatidyl serine valgus and the increase of intracellular calcium concentration in mast cells(p<0.01).At the same time,it significantly down-regulated tumor necrosis factor-?(TNF-?)and inhibited the expression of m RNA in mast cells(p<0.01).Conclusion: Cashew oligopeptide has obvious inhibitory effect on mast cell degranulation induced by DNP-BSA,and inhibits mast cell degranulation by down-regulating the expression of intracellular TNF-?,resulting in anti-allergic effect. |
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