Synthesis, Аntibacterial, Аntifungal, and Antioxidant Activity of New (Benzo)Imidazo[2,1-b][1,3]Thiazine Quaternary Salts

A series of quaternary salts – 1-phenacyl(4-chlorophenacyl)-6-hydroxy-6,7-dihydro-5H-benzo[4,5]imidazo[2,1-b][1,3]thiazinium bromides 4a-f were obtained. Their structures were rigorously proven by the methods of 1H NMR, 13C NMR spectroscopy, and chromatography-mass spectrometry. All obtained compounds were tested in in vitro experiments for antibacterial, antifungal, and antioxidant activity. Bioscreening results showed that 1-(4-chlorophenacyl)-6-hydroxy-6,7-dihydro-5H-benzo[4,5]imidazo[2,1-b][1,3]thiazinium bromide 4f exhibits the highest antibacterial activity against the strain of gram-positive bacteria Staphylococcus aureus ATCC 25923 at a concentration of 125 μg/mL, and salts 4a, c, f – against strains of gram-negative bacteria Pseudomonas aeruginosa ATCC 27853 at a concentration of 62.5 μg/mL. In turn, salt 4c demonstrated the best rate of radical inhibition at the level of 69.3%.