Sulfaquinoxaline (CAS 59-40-5)

Sulfaquinoxaline, a member of the sulfonamide class, serves as a feed additive for the prevention and treatment of poultry leucocytozoonosis and coccidiosis. This sulfonamide antibiotic finds application in veterinary medicine and the meat and poultry industries. Also known as kokozigal or sulfa-Q, sulfaquinoxaline falls within the quinoxalines class of organic compounds, featuring a quinoxaline moiety—a bicyclic heterocycle composed of a fused benzene and pyrazine ring. It is a practically insoluble solid with a relatively neutral nature, primarily residing in the cytoplasm within cells. Primarily used as a veterinary medicine, sulfaquinoxaline is administered to cattle and sheep to combat coccidiosis. Acting as a bacteriostatic agent, sulfonamides impede the synthesis of folic acid in bacterial cells by competing with paraaminobenzoic acid (PABA) for incorporation into the folic acid molecule. This substitution disrupts the formation of folic acid required for DNA synthesis, inhibiting bacterial proliferation. It is important to note that susceptible organisms rely on synthesizing their own folic acid, while mammalian cells utilize preformed folic acid and remain unaffected. Resistance can occur through excess PABA production or environments rich in PABA, which compete with sulfonamides. Sulfonamides act as structural analogs and competitive antagonists of PABA, preventing bacterial utilization of PABA for synthesizing folic acid (pteroylglutamic acid). Specifically, sulfonamides competitively inhibit dihydropteroate synthase, the bacterial enzyme responsible for incorporating PABA into dihydropteroic acid, the immediate precursor of folic acid. Sensitive microorganisms are those that must synthesize their own folic acid, while bacteria capable of utilizing preformed folate are unaffected. Bacteriostasis induced by sulfonamides is counteracted by PABA in a competitive manner. Importantly, this mechanism does not impact mammalian cells, as they require preformed folic acid and lack the ability to synthesize it.