Interaction between Chinese quince fruit proanthocyanidins and bovine serum albumin: Antioxidant activity, thermal stability and heterocyclic amine inhibition

Heterocyclic amines (HCAs) are carcinogenic and mutagenic substances produced in fried meat. Adding natural antioxidants (e.g., proanthocyanidins (PAs)) is a common method to reduce HCAs; however, the interaction between the PAs and protein can affect the inhibitory efficacy of PAs on the formation of HCAs. In this study, two PAs (F1 and F2) with different degrees of polymerization (DP) were extracted from Chinese quince fruits. These were combined with bovine serum albumin (BSA). The thermal stability, antioxidant capacity and HCAs inhi-bition of all four (F1, F2, F1-BSA, F2-BSA) were compared. The results showed that F1 and F2 interact with BSA to form complexes. Circular dichroism spectra indicate that complexes had fewer alpha-helices and more beta-sheets, beta-turns and random coils than BSA. Molecular docking studies indicated that hydrogen bonds and hydrophobic interactions are the forces holding the complexes together. The thermal stabilities of F1 and, particularly, F2 were stronger than those of F1-BSA and F2-BSA. Interestingly, F1-BSA and F2-BSA showed increased antioxidant activity with increasing temperature. F1-BSA's and F2-BSA's HCAs inhibition was stronger than F1 and F2, reaching 72.06 % and 76.3 %, respectively, for norharman. This suggests that PAs can be used as natural an-tioxidants for reducing the HCAs in fried foods.

Automated summary

In this study, two proanthocyanidins (PAs) with different degrees of polymerization (DP) were extracted from Chinese quince fruits and combined with bovine serum albumin (BSA). The results showed that the complexes formed by PAs and BSA had different secondary structures. Molecular docking studies indicated that hydrogen bonds and hydrophobic interactions were the forces holding the complexes together. The thermal stabilities of PAs were stronger than those of PAs-BSA, and PAs-BSA showed increased antioxidant activity with increasing temperature. Furthermore, PAs-BSA had stronger HCAs inhibition than PAs, suggesting that PAs can be used as natural antioxidants for reducing HCAs in fried foods.