Interaction between a Commercial Mannoprotein and Cyanidin-3‑O‑glucoside-4-vinylphenol and Its Stability and Antioxidative Properties as a Novel Functional Pigment

Hydroxyphenyl-pyranoanthocyanins, which are derived from anthocyanins and phenolic acids during the fermentation and aging of red wine, are prone to polymerization and precipitation, which largely limits their application and bioactivity research. In the present study, cyanidin-3-O-glucoside-4-vinylphenol (C3GVP), a hydroxyphenyl-pyranoanthocaynin, was prepared from C3G and p-coumaric acid, and mannoprotein (MP) was employed to improve its stability in various complex solvents by forming a stable anthocyanin–MP complex. We used scanning electron microscopy, ultraviolet–visible spectroscopy, Fourier-transform infrared spectroscopy, and circular dichroism spectroscopy to observe structural changes in C3GVP and MP. The results demonstrated that the intermolecular polymerization of C3GVP was mitigated and the secondary conformation of MP was changed slightly. Fluorescence spectroscopy and molecular docking indicated that C3GVP and MP interacted via hydrogen bonds and hydrophobic interactions. Importantly, the C3GVP–MP complex exhibited better thermal stability and antioxidant capacity than C3G.