Comparative interaction study of soy protein isolate and three flavonoids (Chrysin, Apigenin and Luteolin) and their potential as natural preservatives

Mechanism and functional studies of SPI and Chr/Ap/Lut are reported to exhibit the structure–activity relationship. [Display omitted] •The binding affinity increased with the number of hydroxyl groups on the B-ring.•The antioxidation and foaming ability of SPI are improved by flavonoid addition.•Lut/Ap/Chr can be used as natural preservatives in the fields of food and cosmetics. In this work, the potential of soy protein isolate (SPI)-luteolin (Lut)/apigenin (Ap)/chrysin (Chr) complexes as natural preservatives for food and cosmetics was evaluated by comparing their interactional and functional properties with structure–activity relationship. The results of spectrometry and molecular docking indicated that the B-ring hydroxylation of flavonoids affected their binding constants with SPI, which were determined as Lut (1.45 × 106 L/mol) > Ap (2.04 × 105 L/mol) > Chr (3.81 × 104 L/mol) at 298.15 K. It demonstrated that the hydrogen bonding force played an important role in binding flavonoids to SPI. Moreover, the anti-oxidation ability, antimicrobial effect, and foaming properties were positively correlated with increase in number of hydroxyl groups on the B-ring, but the amount and type of the preservative should be adjusted aimed at the nutrition components. This study provides a theoretical basis for the use of flavonoids and SPI-flavonoid complexes as natural preservatives for food and cosmetics.