EVALUATION OF THE ANTIOXIDANT ACTIVITY OF ACETATES WITH AN IMIDAZOTHIAZINE FRAGMENT

Abstract

This work presents the results of the synthesis of (benz)imidazo[2,1-b][1,3]thiazinyl acetates by acylation of 3-hydroxy(benz)imidazo[2,1-b][1,3]thiazines with acetic anhydride and their further study for antioxidant activity. The first obtained compounds 2a–c were tested for their ability to inhibit the free radical DPPH (1,1-diphenyl- 2-picrylhydrazyl) by spectrophotometric analysis. The antioxidant properties were assessed in methanol medium at a concentration of 5 mM, with the change in optical density recorded after 60 minutes of incubation. This experimental approach allows for efficient and rapid identification of potentially active compounds while optimizing time and materials. Ascorbic acid was used as a reference compound. According to the results of screening studies, it was found that 6,7-dihydro-5H-imidazo[2,1-b][1,3]thiazin-6-yl acetate 2a, 2,3-diphenyl-6,7-dihydro-5H-imidazo[2,1-b][1,3]thiazin-6-yl acetate 2b, and 3,4-dihydro-2H-benz[4,5] imidazo[2,1-b][1,3]thiazin-3-yl acetate 2c exhibit the ability to inhibit DPPH radicals at the level of 61.2 %, 57.7 %, and 56.9 %, respectively. Compound 2a demonstrated the highest antioxidant activity, which allows us to consider it as a promising object for further research towards the development of new synthetic antioxidants. Structural analysis of the studied compounds showed that the presence of diphenyl substituents in the imidazole ring, as well as a condensed benzimidazole core, leads to a decrease in the antioxidant activity of imidazo[2,1-b][1,3]thiazinyl acetates. On the other hand, the presence of an unsubstituted imidazole fragment correlates with an increase in their antiradical activity.