Probing the influence of food colorant on digestive ability: sunset yellow-pepsin system

The binding mechanism of sunset yellow on pepsin was studied by fluorescence quenching method, synchronous fluorescence method, and molecular docking technique. The results showed that sunset yellow can effectively quench the endogenous fluorescence of pepsin, which was accompanied by non-radiative energy transfer. A 1:1 stable complex with a binding constant of 10 4 was formed by sunset yellow and pepsin. The binding site of sunset yellow located in the active center of the pepsin and the binding was driven by electrostatic attraction and hydrogen bonding, thereby changed the conformation of pepsin. The binding rate of sunset yellow was 2.45–1.35% at 310 K, and the binding rate model was W ( Q ) = 5.538 × 10 −6 R 2 −5.188 × 10 −4 R + 0.02494. The binding rate of the pepsin was 2.45–47.11%; the binding rate model was W ( B ) = 2.271 × 10 −4 R 2 + 0.02103 R + 0.009030. Through estimation, it can be seen that when sunset yellow was set at the maximum intake of 0.0025 g at every time, it would reduce the pepsin in gastric juice by 58.79% and seriously affect the body’s digestive function. It was theoretically proved that sunset yellow has serious side effects on human digestive ability. Graphical abstract