Synthesis, theoretical, spectroscopic and electrochemical DNA binding investigations of 1, 3, 4-thiadiazole derivatives of ibuprofen and ciprofloxacin: Cancer cell line studies

Two new 1,3,4-thiadiazole derivatives of ibuprofen and ciprofloxacin namely {(5-(1-(4-isobutylphenyl)ethyl)-1,3,4-thiadiazol-2-amine)} 1 and {(3-(5-amino-1,3,4-thiadiazol-2-y1)-1-cyclopropyl-6-fluoro-7-(piperazin-1-yl)quinolin-4(1H)-one)} 2 were synthesized and characterized by spectroscopic and elemental analysis. DFT and molecular docking were done initially for theoretical binding possibilities of the investigated compounds. In vitro DNA binding investigations were carried out with UV visible spectroscopic, fluorescence spectroscopic, cyclic voltammetric (CV) experiments under physiological conditions of the stomach (4.7) and blood (7.4) pH and at normal body temperature (37 degrees C). Both theoretical and experimental results suggested spontaneous and significant intercalative binding of the compounds with DNA. Kinetic and thermodynamic parameters (K-b, Delta G) were evaluated greater for compound 2 which showed comparatively more binding and more spontaneity of 2 than 1 to bind with DNA at both pH values. Binding site sizes were found greater (n > 1) and revealed the possibility of other sites for interactions along with intercalation. Overall results for DNA binding were found more significant for 2 at Stomach (4.7) pH. Viscometric studies further verified intercalation as a prominent binding mode for both compounds. IC50 values obtained from human hepatocellular carcinoma (Huh-7) cell line studies revealed 2 as potent anticancer agent than 1 as value found 25.75 mu M (lesser than 50 mu M). Theoretical and experimental DNA binding studies showed good correlation with cancer cell (Huh-7) line activity of 1 and 2 and further suggested that these compounds could act as potential anti-cancer drug candidates.