Discovering the antioxidant properties and interaction mechanisms of rosmarinic acid and kaempferol with grass carp hemoglobin: An experimental studies and molecular simulations perspective

The effects of rosmarinic acid (RA) and kaempferol (KMP) on the pro-oxidant capacity of grass carp hemoglobin (Hb) and their interaction mechanisms were explored. Results revealed that in the 0.05–0.2 mg/mL range, RA exhibited superior inhibition of free iron release from Hb. Moreover, the fluorescence mechanism of Hb by RA/KMP was static quenching, and thermodynamic parameters inferred that Hb and RA/KMP spontaneously formed relatively stable complexes facilitated by hydrogen bonding and van der Waals forces. The structural analysis indicated that the interaction of RA/KMP changed the secondary structure of Hb. Besides, molecular docking illustrated that the lowest binding affinity of Hb-RA (−8.799 kcal/mol) > Hb-KMP (−8.626 kcal/mol) exhibited a stronger interaction between Hb and RA. Molecular dynamic simulations further demonstrated that adding RA was more favorable for complex formation. Overall, the interaction between Hb and polyphenols provided valuable insights for selecting antioxidants in freshwater fish preservation. [Display omitted] •RA shows greater inhibition of free iron release from Hb in 0.05–0.2 mg/mL range.•The interactions of RA and KMP with Hb result in static fluorescence quenching.•Adding RA and KMP changes the secondary structure of Hb.•Hb interacts with RA/KMP mainly through hydrogen bonding and van der Waals forces.•Molecular simulations manifest that the Hb-RA complex is more stable than Hb-KMP.