Ultrasound-assisted complexation of Millettia speciosa by-product protein with polyphenols: improved structural properties, antioxidant and hypoglycemic activities, and gut microbiota modulation.

Abstract

This study utilized ultrasound-assisted technology to form non-covalent complexes of polyphenols with Millettia speciosa by-product protein (MSCP). Ultrasound disrupted protein aggregates into a porous network, increasing surface area. Polyphenol binding shifted protein structure from α-helix to β-sheet and enhanced hydrogen bonding. The complexes showed strong antioxidant and hypoglycemic activities, with the tannic acid (TA) complex comparable to vitamin C in radical scavenging and to acarbose in enzyme inhibition under the tested conditions. Fermentation experiments revealed the modified proteins enriched beneficial bacteria (e.g., Bacteroidetes, Phascolarctobacterium), increased microbial diversity, and showed predicted enrichment of metabolic pathways. The quercetin (QR) complex behaved similarly to inulin, while the TA complex promoted beneficial bacteria and suppressed pathogens. This approach improves MSCP's functionality, offering a sustainable strategy for its use in functional foods and biomaterials.