Secondary Sulfonamides as Effective Lactoperoxidase Inhibitors.

Secondary sulfonamides ( 4a - 8h ) incorporating acetoxybenzamide, triacetoxybenzamide, hydroxybenzamide, and trihydroxybenzamide and possessing thiazole, pyrimidine, pyridine, isoxazole and thiadiazole groups were synthesized. Lactoperoxidase (LPO, E.C.1.11.1.7), as a natural antibacterial agent, is a peroxidase enzyme secreted from salivary, mammary, and other mucosal glands. In the present study, the in vitro inhibitory effects of some secondary sulfonamide derivatives ( 4a - 8h ) were examined against LPO. The obtained results reveal that secondary sulfonamide derivatives ( 4a - 8h ) are effective LPO inhibitors. The Ki values of secondary sulfonamide derivatives ( 4a - 8h ) were found in the range of 1.096 × 10-3 to 1203.83 µM against LPO. However, the most effective inhibition was found for N -(sulfathiazole)-3,4,5-triacetoxybenzamide ( 6a ), with Ki values of 1.096 × 10-3 ± 0.471 × 10-3 µM as non-competitive inhibition.