Preliminary Evaluation of HSA and DNA Interactions with Indole-Thiosemicarbazone Compounds and Molecular Docking Studies

Abstract Indole-thiosemicarbazones have different biological activities. The present study evaluated the preliminary interaction of these compounds with biomolecules, specifically human serum albumin (HSA) and DNA, using fluorescence techniques. The suppression results (Ksv) for HSA ranged from 3.5 x 104 to 4.6 x 105 L/mol, while for DNA, they ranged from 1.4 x 104 to 5.9 x 104 L/mol. The suppression was classified as weak to strong for HSA and moderate for DNA. The bimolecular suppression constant (Kq) showed values between 6.0 x 1012 and 8.2 x 1013 L/mol/s for HSA and from 1.4 x 1012 to 5.9 x 1012 L/mol/s for DNA, suggesting a static suppression mechanism. Compound PR09 stood out, presenting a binding constant (Ka) greater than 105 L/mol for HSA, indicating a strong interaction. Additionally, PR05, PR06, PR07, and PR09 demonstrated strong interactions with DNA. The values of the number of binding sites (n) indicated that PR01, PR02, and PR09 bind to multiple sites on HSA, while PR04, PR05, PR06, and PR09 interact with more than one site on DNA. All interactions were spontaneous, with ∆G negative. The distance between the compounds and tryptophan on HSA was less than 8 nm, suggesting high energy transfer efficiency. In molecular docking studies, PR05 showed the highest affinity for DNA (-11.15 kcal/mol), while PR09 had the highest affinity for HSA (-10.00 kcal/mol). PR07 exhibited the lowest binding energies for DNA (-8.21 kcal/mol) and for HSA (-7.38 kcal/mol). This study demonstrates that the evaluated compounds have potential as new drug candidates.