改性前后小米糠膳食纤维结构分析及体外抑制α-葡萄糖苷酶活性

摘要

以小米糠为实验材料,利用超声-微波协同法对气爆预处理的小米糠膳食纤维(millet bran dietary fiber, MBDF)进行改性;借助扫描电子显微镜、凝胶色谱-示差-多角度激光光散射(gel permeation chromatography-refractive index-multi angle light scattering,GPC-RI-MALS)、X射线衍射、傅里叶变换红外光谱和离子色谱法对改性前后小米糠膳食纤维的结构进行研究;通过建立α-葡萄糖苷酶抑制剂体外模型,研究改性前后小米糠水溶性膳食纤维(soluble dietary fiber,SDF)对α-葡萄糖苷酶活性的抑制作用.扫描电子显微镜结果显示,改性小米糠SDF的颗粒表面变得粗糙、疏松多孔,由小颗粒聚集而成;GPC-RI-MALS分析表明,改性小米糠SDF的重均相对分子质量变小;X射线衍射分析显示,改性小米糠不溶性膳食纤维的结晶度上升;红外光谱分析表明,改性小米糠SDF化学官能团变化不大,呈现出明显的糖类特征吸收峰;离子色谱结果显示,改性前后小米糠SDF都含有阿拉伯糖、半乳糖、葡萄糖、木糖、甘露糖、果糖,但两者在含量上存在差异;改性前后小米糠SDF均有抑制α-葡萄糖苷酶活性的作用,其中改性小米糠SDF对α-葡萄糖苷酶活性的抑制作用较强,其半抑制浓度为0.415 mg/mL.%Millet bran dietary fiber (MBDF) was modified by combined ultrasonic-microwave treatment in this study. The structures of the original and modified MBDF were investigated by means of scanning electron microscope (SEM), gel permeation chromatography-refractive index-multi-angle light scattering (GPC-RI-MALS), X-ray diffraction, infrared spectroscopy and ion chromatography. The inhibitory effect of the original and modified soluble dietary fiber (SDF) from millet bran on α-glucosidase activity was explored using in vitro α-glucosidase inhibitor model. SEM images showed that the surface of SDF became rough, loose and porous after modification and was composed of aggregated small particles. The results of GPC-RI-MALS indicated that the molecular mass of modified millet bran SDF was smaller than that of the original one. The crystallinity of the modified insoluble dietary fiber from millet bran was increased as indicated by X-ray diffraction analysis. Fourier transform infrared spectroscopic analysis illustrated that the chemical functional groups of the original millet bran SDF did not change after modification. Both the original and modified millet bran SDF had the characteristic absorption peaks of carbohydrates. Ion chromatography showed that both the original and modified millet bran SDF were composed of arabinose, galactose, glucose, xylose, mannose and fructose, with differences being observed in the monosaccharide contents. Both the original and modified millet bran SDF could inhibit the activity of α-glucosidase, while the inhibitory effect of modified millet bran SDF was stronger than that of the original one, with a half-maximal inhibitory concentration of 0.415 mg/mL.