Abstract: Wheat bran is rich in phenolic compounds,which exhibit significant antioxidant,anti-inflammatory,antihypertensive,and anti-atherosclerotic effects both in vitro and in vivo,making them important functional components.Phenolic compounds exist in free forms,soluble bound forms,and insoluble bound forms,with the majority being in bound forms,typically associated with dietary fiber through hydrogen bonding,hydrophobic interactions,covalent bonding,or physical entrapment,thus forming dietary fiberphenolic complexes.The content of phenolics bound to dietary fiber can be as high as 90% in grains.The physiological properties of these dietary fiber-phenolic complexes are similar to those of dietary fiber,which are not degradable by digestive enzymes,and affect the absorption of phenolics in the human body.Therefore,it is crucial to understand how to disrupt this structural constraint and release more phenolic substances to enhance their bioavailability and regulate the functional value of wheat bran.This study aims to increase the release of free phenolics (FP) from wheat bran and explore the functional properties of FP extract.A combined treatment of superfine grinding and enzymes was employed to modify wheat bran.Using FP release amount as the evaluation criterion,single-factor experiments were conducted to study three factors:enzyme hydrolysis pH,enzyme hydrolysis temperature,and liquid-to-solid ratio.Response surface optimization experiments were then carried out based on these three factors.ABTS and DPPH radical scavenging activities and the inhibitory effect of α-glucosidase of the optimized wheat bran FP extract were also investigated,along with the analysis of phenolic acid components.The results showed that the optimal parameters for releasing FP from wheat bran were an enzymatic hydrolysis temperature of 52℃,a liquid-to-solid ratio of 45 mL/g,and an enzymatic hydrolysis pH of 4.3.Under these conditions,the FP release per gram of bran (Gallic Acid Equivalent) was (6.25±0.26) mg/g,representing a 61.08% increase in FP release after modification.The optimized wheat bran FP extract exhibited strong ABTS and DPPH radical scavenging abilities,with IC₅₀ values decreased by 52.72% and 46.52%,respectively.The inhibitory effect of the composite-modified wheat bran FP extract on α-glucosidase was significantly enhanced (P < 0.05),with inhibition increasing in a concentration-dependent manner within the range of 12.5 to 200 mg/mL.The analysis of FP compounds in wheat bran was conducted using Ultra-Performance Liquid Chromatography-Triple Mass Spectrometry (UPLC-MS/MS).A total of seven phenolic acids were identified,with ferulic acid being the most abundant free phenolic acid after composite modification.It accounted for 69.28% of free phenolic acids and showed a 7.42-fold increase in release.This study demonstrated that the free phenolics extract from the combined treatments exhibited excellent antioxidant and hypoglycemic activities in vitro,and explored the changes in phenolic acid composition before and after wheat bran modification.The findings provide a reference for the rational utilization of phenolic compounds in wheat bran and the enhancement of its added value.