Understanding the combined effect and inhibition mechanism of 4-hydroxycinnamic acid and ferulic acid as tyrosinase inhibitors.

The development of tyrosinase inhibitors to prevent the enzymatic browning have become a research hotspot in food industry. 4-Hydroxycinnamic acid (CA) and ferulic acid (FA) are both the derivates of cinnamic acids, which are widely coexisted in plants seeds and leaves. CA combined with FA (inhibition rate of 90.44%) were found to effectively inhibit tyrosinase activity than employing CA and FA alone (inhibition rate of 12.15% and 22.17%, respectively). CA-FA-tyrosinase complex resulted in fluorescence quenching. The first-order kinetics and Weibull models well described the inactivation of tyrosinase at 2-4 mM and 6-10 mM of CA and FA, respectively. Additionally, UV-vis spectrum indicated that several characteristic groups such as hydroxyl group in CA competed with the nucleophilic attack of intramolecular cyclization, leading to the decrease of characteristic peak. Molecular docking further studied that CA and FA interacted with the activity cavity of tyrosinase by amino acids residues Ser282, His263, and Val283.