Abstract: Proanthocyanidins (PCs) are a broad superfamily of bioactive substances, which belong to a class of flavonoids. However, because of their instability against wet, sunlight or high temperature, their application in food, medicine, and health products is restricted. In this paper, purified apoferritin (AFt) and PCs were prepared and used to prepare apoferritinproanthocyanidins complex (AFt-PCs). The interaction of AFt with PCs was studied by using fluorescence spectroscopy, circular dichroism (CD) spectroscopy, and transmission electron microscopy (TEM). Meanwhile, the stability of free PCs and PCs in AFt-PCs under different conditions of light and temperature was compared. It was found that PCs significantly quenched the fluorescence of AFt, and the binding number n of PCs to AFt through the model fitting was 0.07:1 (PCs/AFt, m/m), with an apparent binding constant K of (2.03 ± 0.08) ×104 L/mol. PCs did not change the secondary structure of AFt to a significant extent. TEM results exhibited a certain degree of polymerization of Aft by the induction of PCs. In addition, the stability of PCs in AFt-PCs against light and temperature was higher than that of free PCs. This work provided a method to explore the multicomponent interaction in food and to improve the stability of PCs.

Key words: proanthocyanidins, ferritin, stability