Abstract:This study aimed to investigate the effects of covalent conjugation with tea polyphenols （TP） on the structure and bioactivity of arabinoxylan （AX）. AX-TP covalent complexes were prepared using a free radicalinitiated method. Regarding structural characterization，the TP grafting rate and changes in AX solubility were analyzed using the Folin-Ciocalteu method and a centrifugation method，respectively. Monosaccharide composition changes were determined by acid hydrolysis coupled with GC-MS，and conformational characteristics were investigated using a high-performance size-exclusion chromatography system coupled with multi-angle laser light scattering （HPSEC-MALLS）. For bioactivity assessment，the antioxidant properties of the complexes were studied in a Caenorhabditis elegans model，and an in vitro fermentation model using porcine colonic digesta was employed to compare the colonic fermentation characteristics of the complexes with those of TP and AX alone. The results showed that the free radical method achieved a TP grafting rate of （59.60±2.40） mg TP/g onto AX，although this significantly reduced the solubility of AX （P＜0.05）. Structural analysis revealed that the conjugation process did not alter the monosaccharide composition or conformational features of AX but did increase its molecular weight. Bioactivity assays demonstrated that covalent binding of TP enhanced the antioxidant capacity in C. elegans，increasing the activities of superoxide dismutase （SOD） and catalase （CAT） by 24.8% and 19.0%，respectively，while reducing reactive oxygen species （ROS） levels by 42.9%. Furthermore，although the covalent linkage of TP partially attenuated the prebiotic activity of AX，the complexes still effectively promoted the proliferation of beneficial bacteria，such as Lactobacillus， Bifidobacterium，and Terrisporobacter，and inhibited the growth of potentially harmful bacteria，such as Escherichia-Shigella and Streptococcus.In summary，compared to AX or TP alone，the AX-TP covalent complex exhibits potential antioxidant and prebiotic functions. This study elucidates the covalent binding mechanism between AX and TP and its regulatory effects on the structure and function of the resulting complex. These findings provide a theoretical basis for the precise preparation of novel polysaccharide-polyphenol complexes and offer practical guidance for their application in functional foods and nutraceuticals.