Abstract: Three delignification-assisted extraction approaches were employed for arabinoxylan (AX) isolation from sugarcane bagasse, namely direct alkaline extraction, one-step H2O2-NaOH extraction, and two-step H2O2-NaOH extraction. Their impacts on the extraction efficiency, physicochemical properties, and structural features of AX were systematically compared, and the glucose adsorption capacity, glucose diffusion inhibitory effect, and in vitro digestive enzyme inhibitory activities of the extracted products were evaluated. Results indicated that the one-step extraction method exhibited the most prominent advantages, achieving the highest dissolution rate (94.85%), recovery rate (97.50%), and purity of AX; the water-soluble and water-insoluble fractions reached purities of 95.22% and 88.84%, respectively. Although the two-step method showed a slightly higher dissolution rate (95.27%), its recovery rate was only 77.31%, and the purity of the water-insoluble fraction was significantly lower (52.98%). The molecular masses of the water-soluble and water-insoluble AX obtained by the three methods followed a consistent trend: direct alkaline extraction > one-step method > two-step method. Specifically, the molecular masses of the water-insoluble AX fractions were 8.55 × 105, 7.15 × 105, and 4.65 × 105 Da, respectively. The whiteness values of the water-soluble and water-insoluble AX obtained by one-step extraction were 91.42 and 90.80, respectively. Scanning electron microscopy (SEM) observation revealed no significant differences in the micromorphology of the products. Monosaccharide composition analysis demonstrated that sugarcane bagasse AX was mainly composed of eight monosaccharides (including xylose and arabinose) and uronic acid, with the water-soluble fraction exhibiting a richer monosaccharide profile and a higher arabinose/xylose (A/X) ratio than the water-insoluble fraction. In terms of biological activities, the AX extracted by direct alkaline extraction showed the highest glucose adsorption capacity (378 mg/g for the water-soluble fraction and 282 mg/g for the water-insoluble fraction), which was significantly higher than that of the one-step method (all 241 mg/g) and the two-step method (141 and 46 mg/g, respectively). The glucose diffusion inhibitory effect of the water-insoluble fraction was stronger than that of the water-soluble fraction, irrespective of the extraction method used. In vitro digestive enzyme inhibitory activity assays showed that the products at high concentrations exhibited varying degrees of inhibitory effects on four digestive enzymes. Specifically, the inhibitory activities of water-soluble AX against α-amylase, maltase, and sucrase were more potent than those of water-insoluble AX. Among the three extraction methods, the water-soluble AX prepared by the two-step method displayed the strongest inhibitory activity, with half maximal inhibitory concentration (IC50) values of 34.25 g/L for α-amylase, 38.40 g/L for maltase, and 24.85 g/L for sucrase. In contrast, the α-glucosidase inhibitory activity of the water-soluble fraction was weaker than that of the water-insoluble fraction. In conclusion, delignification methods significantly affected the extraction efficiency, physicochemical properties, and biological activities of AX. The one-step method was superior in terms of dissolution rate, recovery rate, purity, and whiteness. The AX extracted by the direct alkaline method exhibited the best glucose adsorption and diffusion inhibition activities. The water-soluble AX fraction showed stronger inhibitory effects on digestive enzymes than the water-insoluble fraction.

Key words: sugarcane bagasse; arabinoxylan; delignification; extraction; enzyme activity inhibition