Synthesis, characterization, investigation of antioxidant and enzyme activities of Schiff base derivatives containing benzothiazole

Benzothiazole is a heterocyclic compound containing nitrogen and sulfur atoms. It is known that structures containing heteroatoms such as nitrogen, sulfur and oxygen show pharmacological activity. Structure-activity studies have revealed that the biological activity of benzothiazole compounds changes significantly with their derivatization from the 2-position. For this reason, 2-position derivatizations of benzothiazole compounds and the investigation of their biological activities have an important place in the literature. In the derivatization of benzothiazoles from the 2- position, Schiff bases can be obtained by reactions of amine derived benzothiazole compounds with different aldehydes and ketones. Schiff bases contain the azomethine functional group (-C=N) and their biological activities are widely studied in the literature. It is known that the unshared electrons on the nitrogen atom of the azomethine group affect cell processes by forming hydrogen bonds between the active centers of cell components. For this reason, it is expected that Schiff bases containing a benzothiazole skeleton will be biologically active. It has been reported in the literature that the derivatives synthesized by combining these two biologically active units exhibit a wide variety of biological activities such as anticancer, antimicrobial, antimalarial and fungicidal. Within the scope of this thesis, 12 target benzothiazole-azomethine compounds (3a3l), 7 of which are original, were synthesized. Spectroscopic characterizations of all synthesized structures were carried out by FT-IR, UV-vis, 1H NMR and 13C NMR methods. The enol-imine and keto-amine tautomer equilibrium was observed in the synthesized derivatives and the tautomer equilibrium was investigated by UV-visible spectroscopic measurement in DMF organic solvent in acidic and basic media. It was determined that the compounds prefer keto-amine form in basic medium and enolimine form in acidic medium. Antioxidant and enzyme activities of all synthesized derivatives were investigated. Antioxidant activity measurements were carried out using two different methods: 2,2-diphenyl-1-picrylhydrazyl radical scavenging capacity (DPPH) and ferric reducing antioxidant power (FRAP) methods. When the antioxidant activity results of both methods were analyzed, it was determined that (3j-3l) compounds showed the highest activity. The enzyme activities of the compounds were also studied against 4 different enzyme types. These enzymes are α-glucosidase, tyrosinase, acetylcholinesterase and butyrylcholinesterase. Among the synthesized benzothiazole-azomethine derivatives, only (3g-3i) derivatives showed good enzyme inhibition activity against α-glucosidase enzyme. The lack of activity against other types of enzymes indicates that the (3g-3i) derivatives are selective for a certain enzyme.