Experimental and Theoretical Approaches to Monitor the Behavior of Bovine Liver Catalase in Interaction with a Binuclear Bismuth Complex.

Here, the antioxidant potency of a binuclear Bi(III) complex {[Bi(μ-ox)(dipic)(HO) (taa)].HO, where ox = oxalato, dipic = pyridine 2,6-dicarboxylato, and taa = thiourea} was evaluated using the •DPPH assay. It was demonstrated that the Bi complex exhibited a high ability to inhibit DPPH free radicals. The binding mechanism of the complex with bovine liver catalase (BLC) was also investigated, revealing structural and activity changes in the enzyme in the presence of the complex. The catalase activity in the decomposition of hydrogen peroxide increased in the presence of the Bi complex, reaching 39.8% higher than its initial activity at a concentration of 7.77 × 10 M. The complex exhibited a relatively high affinity for BLC, with values of 3.98, 0.13, and 0.09 × 10 M at 303, 310, and 317 K, respectively. The mechanisms involved in the interaction were hydrogen bonding and van der Waals interactions, as validated through molecular docking simulations. Synchronous fluorescence showed that tryptophan was more affected by enzyme-complex interactions than tyrosine. In addition, a cell viability test using the MTT method revealed that at its highest concentration, the Bi complex caused a decrease in the number of cells below 50% compared to the control, while cisplatin showed negative effects at all concentrations. These findings suggest that the Bi complex has the potential to be developed as a promising candidate for BLC-related therapeutic target therapy.