| Pumpkin skin is a by-product of pumpkin processing,which is used as waste treatment,the comprehensive utilization is low.Polysaccharides,as the main active ingredient of pumpkin,have great potential in the development of health food and research on pharmacological effects.Zinc is vital to human body and has various biological activities such as antioxidant,antiseptic and anti-inflammatory,promoting growth and development,participating in the regulation of various enzymes and improving immunity.Chemical modification of zinc on PSP can enrich and improve the bioactivity of polysaccharides,and also promote the absorption and utilization of zinc for human body as well as increase the added value of pumpkin skin.In the study,PSP-Zn were prepared by zinc sulfate method,and structural characterization,physicochemical properties,bioavailability and anti-inflammatory activity were investigated.The main research contents and results are as follows.(1)Preparation of PSP-ZnPSP-Zn were prepared by zinc sulfate method.The optimum preparation process was optimized by single-factor and response surface method:the weight ratio of PSP to zinc was18?1,the reaction time was 104 min,the reaction temperature was 50?,and the p H was 9,the maximum chelation rate was 99.37±0.12%.(2)Structural characterization of PSP-ZnHigh performance gel permeation chromatography,ionic chromatography,circular dichroism,spectral analysis,scanning electron microscopy,X-ray diffraction,particle size and thermogravimetric analysis were used for the structural characterization of PSP-Zn.The results showed that the monosaccharide composition of PSP-Zn was rhamnose:arabinose:galactose:glucose:galacturonic acid=1.96?3.01?6.81?81.54?6.68,the molecular weight increased from 3.034×10~6 Da to 3.222×10~6 Da.Circular dichroism analysis showed that a new absorption peak appeared at 206 nm,which showed changes in the polysaccharides conformation.PSP-Zn was attached by Zn-O bond,with a flat surface and relatively compact structure of thick flakes.The particle size of PSP-Zn was 136.2?157.2 nm.PSP-Zn had an amorphous structure,and the crystal content became low after chelation.(3)Study on the properties of PSP-ZnPhysicochemical properties analysis showed that the polysaccharides changed from white powder to white cotton flocculent,but the basic composition and physicochemical properties of PSP-Zn did not change significantly.The stability analysis showed that the compound became less stable with the extension of storage time and the increase of storage temperature,and its storage effect in neutral environment was better than that in strong acid and strong alkaline environment.(4)Study on bioavailability of PSP-ZnIn vitro simulated gastrointestinal digestion was used to compare the bioavailability of PSP-Zn and inorganic zinc.The results showed that the zinc solubility of PSP-Zn and inorganic zinc were 12.76%and 50.52%in artificial gastric juice.The zinc solubility of PSP-Zn and inorganic zinc were 2.18%and 0.13%,and the dialysis rates were 16.59%and 0.56%in artificial intestinal fluid.The bioavailability of PSP-Zn was superior to that of inorganic zinc.(5)Study on the anti-inflammatory activity of PSP-ZnThe PSP groups and PSP-Zn groups could significantly inhibit the migration of macrophages to zebrafish test lines,and the cell migration rate decreased by 21.54%?47.69%and 26.15%?49.23%,respectively,and the anti-inflammatory effect was better than or close to that of positive control drug ibuprofen.The real-time fluorescence quantitative PCR results showed that PSP-Zn inhibit the inflammatory response mainly by suppressing the gene expression of inflammatory factors such as nos2b,i NOS,IL-6 and NF-?B2.The results showed that the anti-inflammatory activity of some pathways increased after the binding of PSP with zinc. |
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