| There is a high content of oat ?-glucan in oat bran.Oat ?-glucan is a water-soluble dietary fiber.It has various physiological functions,such as lowering blood sugar,enhancing the body's resistance to disease,and maintaining the growth of microbe in the intestine.High-purity ?-glucan was extracted from oat bran.It was oxidized with TEMPO/NaBr/NaClO system,and the oxidized ?-glucan was used as carrner to prepare nanocomposites with curcumin.A preliminary study of the structure and properties of nanocomposites was conducted.The purity of crude ?-glucan obtained by alkali extraction was 83.59±1.51%.The crude ?-glucan was purified with ammonium sulfate to reach a purity of 89.44±1.24%.The intrinsic viscosity of ?-glucan was 3.52 dL/g,and the weight-average molecular mass was 6.45×105 g/mol.1H and 13C NMR results showed that the glucose residual in ?-glucan was linked with ?-(1?4)and ?-(1?3)glycosidic bonds.The ratio of ?-(1?4)to ?-(1?3)glycosidic bonds was about 2.1:1.Oat ?-glucan was oxidized ?-glucan with TEMPO/NaBr/NaClO system.The single factor analysis showed that the reaction time,pH of the solution,and the volume of the NaClO solution had significant effects on the degree of oxidation of ?-glucan,but the influence of reaction temperature was not obvious.The results of response surface experiment showed that the optimum oxidation conditions were as follows:the reaction time was 1 h,the pH of the solution was 11,and the volume of NaClO solution was 180 ?L.Oat ?-glucan was oxidized under this condition to produce a degree of oxidation of 13.78%.The structure and properties of oxidized ?-glucan were characterized and the results are as follows:The intrinsic viscosity of oxidized ?-glucan was 0.36 dL/g,and the weight average molecular mass was 3.69×104 g/mol.The results of 13C NMR,fourier transform infrared(FT-IR)spectroscopy and Raman spectroscopy showed that there were carboxyl groups in the oxidized ?-glucan.The results of X-ray diffraction(XRD)showed that?-glucan existed in the form of amorphous solids before and after oxidation,and there was no significant change in the structure.The zeta potential of oxidized ?-glucan was-23.22 mV,indicating that it has strong negative charge.The results of scanning electron microscopy(SEM)showed that the structure of 8-glucan was denser after oxidation by TEMPO system.A 2 mg/mL oxidized ?-glucan solution and a 5 mg/mL curcumin stock solution were mixed to prepare water-soluble curcumin nanocomposites.The results showed that the nanocomposite had a particle size of 138 nm and zeta potential of-20.15 mV.The loading rate of curcumin was 75.38%and the actual loading was 22.61 ?g/mg.DPPH and ABTS free radicals can be eliminated by the curcumin nanocomposites.FT-IR spectroscopy showed that oxidized ?-glucan and curcumin combined to form nanocomposites through intermolecular interactions.The results of XRD showed that the components in the nanocomposite existed in an amorphous state.Atomic force microscopy(AFM)showed that the nanocomposite had good rehydration ability.The in vitro release studies showed that the release of curcumin from nanocomposites in simulated gastric and intestinal fluids was superior to from curcumin ethanol solution. |
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