Exploring the Binding Mechanism of Whey Protein Isolate‐Quercetin Complex and Its Protective Effect Against Dexamethasone‐Induced Muscle Atrophy

ABSTRACT Whey protein isolate (WPI) is a promising carrier for bioactive compounds, yet its application for muscle health requires further investigation. This study constructed a WPI‐Quercetin (Que) complex using the pH‐shift method and evaluated its binding mechanism, structural evolution, and mitigating effects on dexamethasone (DEX)‐induced muscle damage. The complex achieved optimal stability at a 1:40 Que: WPI mass ratio, characterized by a sulfhydryl (SH) content of 5.94 μmol/g, a particle size of 427 nm, a Polydispersity Index (PDI) of 0.28, and a zeta potential of −32.1 mV. Multispectral analysis and molecular docking suggested that Que primarily embeds into the hydrophobic cavity of WPI through hydrophobic interactions and hydrogen bonds, inducing protein secondary structure rearrangement. In vitro experiments using C2C12 myotube models demonstrated that the WPI‐Que complex significantly enhanced myosin heavy chain (MHC) expression, increased myotube diameter, and improved the fusion index, both in the presence and absence of DEX stimulation. Furthermore, RT‐qPCR and Western blot analyses indicated that the WPI‐Que complex upregulates myogenic regulators more effectively than WPI or Que alone. These findings indicate that the WPI‐Que complex possesses both structural stability and biological activity, offering a theoretical foundation for developing novel functional food ingredients to counteract muscle decline.