Abstract
(Z)-4-(4-cyanophenylamino)-4-oxobut-2-enoic acid (LH) and its new triphenyltin (IV) derivative (Ph3SnL) were synthesized and further investigated for their binding with ds.DNA under physiological conditions {pH: 4.7 (stomach); 7.4 (blood), 37°C} using UV–Visible/fluorescence spectroscopy, cyclic voltammetry and viscosity measurement techniques. Spectral responses as well as experimental findings from all the techniques i.e., binding constant (Kb), binding site size (n) and free energy change (ΔG) correlated with each other and indicated formation of spontaneous compound–DNA complexes via intercalation of compounds into the DNA base pairs. Values of kinetic parameter, Kb, revealed comparatively greater binding of both the compounds with DNA at stomach pH (4.7). However among both compounds organotin complex (Ph3SnL) showed comparatively greater binding than that of its ligand (LH) as evident from its, Kb, values at both the pH values. In general, Kb values were evaluated greater for Ph3SnL at stomach pH {: Kb: 8.65×104M−1 (UV); 5.49×104M−1 (fluorescence); 8.85×104M−1 (CV)}. Voltammetric responses of both compounds before and after the addition of DNA indicated that diffusion controlled processes are involved. Complex Ph3SnL exhibited the best antitumor activity.