Raubasine-Induced Groove Binding in Salmon Testes DNA: Exploring the Structural Modulation, Antiglycation, and Antioxidant Properties

As one of nature's most fundamental blueprints and due to its critical role in life processes, DNA has naturally become the cornerstone of numerous research efforts. One particularly intriguing area of study is understanding how small molecules interact with nucleic acids. In this study, we investigated the interaction between the plant-derived indole alkaloid Raubasine (Ajmalicine; AJM) and Salmon Testes (ST) DNA using biophysical and computational techniques. A hyperchromic shift in the fluorescence intensity indicated the effective binding of AJM to ST DNA. The binding constant was in the order of 10⁵ M^-1 with a single preferential binding mode. Thermodynamic analysis revealed that exothermic binding was driven by positive entropy and negative enthalpy. The salt-dependent fluorescence analysis indicates the involvement of nonpolyelectrolytic forces in the interaction. Studies of iodide quenching, urea denaturation, dye displacement, and molecular docking further support that AJM binds to ST DNA through groove binding. Structural perturbation of DNA was evident from circular dichroism. The stability of the AJM-DNA complex was confirmed by molecular dynamics simulations. Prolonged elevated blood glucose levels induce nonenzymatic glycation of DNA, resulting in DNA-AGE (advanced glycation end-products) formation and free radical production, which disrupts the DNA structure. We explored ST-DNA glycation and its suppression by AJM. DNA-AGEs in vitro were characterized using UV-vis and fluorescence spectroscopy. The inhibition of glycation by AJM was assessed through changes in AGEs fluorescence intensity, gel electrophoresis patterns, and antioxidant activity, highlighting its ability to target glycated sites or neutralize free radicals generated during glycation. Our findings reveal AJM's potential to prevent the formation of AGEs, which may offer promising avenues for targeted therapies against glycation-related diseases such as diabetes, neurodegeneration, and cancer.