Spectroscopic and in silico data indicate that phenolic acids interact with aldose reductase with different degrees of affinity at a single binding site.

Our previous studies demonstrated that the enzyme aldose reductase (AR) is activated by its interaction with tubulin, a mechanism which can lead to the emergence of secondary diseases in diabetic patients. We also found that different compounds derived from phenolic acid (CAFs) can prevent this interaction and thus AR activation. Here, we used spectroscopic and bioinformatic techniques to explore the interaction between AR and three CAFs: 3-nitrotyrosine (NTyr), Tyrosine (Tyr), and vanillic acid (Van). The results revealed that the CAFs alter the UV-Vis absorption spectrum of AR and significantly quenchAR fluorescence. These changes suggest the formation of stable AR-CAF complexes. Moreover, a single binding site for the CAFs was identified in AR, to which a single molecule of NTyr and at least two molecules of Tyr or Van appear to bind. NTyr showed the most affinity for interacting with the enzyme, followed by Tyr and Van. Binding occurs through a thermodynamically favorable and exothermic process. It involves van der Waals interactions and the creation of hydrogen bonds between the phenol substituent in the CAFs and the side residues in AR. Molecular docking calculations confirmed NTyr as the compound with the most affinity and revealed the multiple interactions that contribute to this affinity. These findings enhance our understanding of the molecular mechanisms through which different CAFs bind to AR and inhibit its interaction with tubulin. As such, they could pave the way for the design of novel adjunctive treatments that complement conventional antihyperglycemic therapies and mitigate complications associated with diabetes mellitus.