Electrochemical oxidation and superoxide radical scavenging activity of 2-hydroxy/methoxy-phenylbenzothiazole derivatives

Electrochemical characterisation and antioxidant activity against superoxide radical anion of four 2-hydroxy/ methoxy-phenylbenzothiazole derivatives (1-4) are reported. The electrochemical oxidation was studied at a glassy carbon electrode using square-wave voltammetry in an aqueous buffer solution (pH = 1-12). In 1 (2-(2-methoxyphenyl)benzothiazole-6-ammonium chloride) and 2 (2(2-hidroxyphenyl)benzothiazole-6-ammonium chloride), the benzothiazole C6-amino group was the main electroactive centre, undergoing a complex, pH-dependent process, coupled to the follow-up chemical reaction. The initial electrode reaction of 3 (6-(4,5-dihydro-1H-imidazol-3-ium-2-yl)-2-(2,3,4-trihydroxyphenyl)benzothiazole chloride) and 4 (6-amidinium-2-(2,3,4-trihydroxyphenyl)benzothiazole chloride) is a quasireversible, twoelectrons, two-protons oxidation of the pyrogallol group. Superoxide radical scavenging activity was evaluated by means of cyclic voltammetry and computational analysis, which was revealed to rely on their ability to undergo the hydrogen atom transfer. In 1 and 2, H center dot donation from the benzothiazole C6-amino group is favoured, while a considerable improvement in the antioxidant activity was achieved in systems with the pyrogallol moiety 3 and 4, where it is realized from the middle 2-hydroxyl group, which allows for the formation of a stable O-H center dot center dot center dot O center dot center dot center dot center dot H-O fragment following the H center dot liberation.

Automated summary

This study reports on the electrochemical properties and antioxidant activity of four 2-hydroxy/methoxy-phenylbenzothiazole derivatives. The results show that two derivatives have the main electroactive center at the C6-amino group of the benzothiazole molecule, while the other two derivatives have the main electroactive center at the pyrogallol group.