Sulfadoxin-d₄is intended for use as an internal standard for the quantification of sulfadoxin by GC- or LC-MS. Sulfadoxin is a sulfonamide antibiotic that inhibits dihydropteroate synthetase (DHPS), an enzyme involved in folic acid synthesis.¹Sulfadoxin competes with 4-aminobenzoate (PABA), the native substrate of DHPS, and inhibits PABA incorporation into folic acid.²Folate is essential for purine and pyrimidine synthesis, therefore, sulfadoxin has antiproliferative activity in non-resistantP. falciparum.^2,3Sulfadoxin inhibits growth ofP. falciparumin vitro, but potency varies between non-resistant (IC₅₀= 4 ng/ml) and resistant strains (IC₅₀= 3,970 ng/ml).³

1.Brooks, D.R., Wang, P., Read, M., et al.Sequence variation of the hydroxymethyldihydropterin pyrophosphokinase: dihydropteroate synthase gene in lines of the human malaria parasite, Plasmodium falciparum, with differing resistance to sulfadoxineEur. J. Biochem.224(2)397-405(1994) 2.Hyde, J.E.Exploring the folate pathway in Plasmodium falciparumActa. Trop.94(3)191-206(2005) 3.Wang, P., Read, M., Sims, P.F.G., et al.Sulfadoxine resistance in the human malaria parasite Plasmodium falciparum is determined by mutations in dihydropteroate synthetase and an additional factor associated with folate utilization.Mol. Microbiol.23(5)979-986(1997)