Novel disulfonated tetrazolium salt that can be reduced to a water-soluble formazan and its application to the assay of lactate dehydrogenase

A new tetrazolium salt, 4-[3-(4-iodophenyl)-2-(2,4-dinitrophenyl)-2H-5-tetrazolio]-1,3-benzene disulfonate, sodium salt, that produces a highly water-soluble formazan dye upon reduction by reduced nicotinamide adenine dinucleotide (NADH) was synthesized. The reduction of the compound by NADH at a neutral pH is fast owing to its small reduction potential. The applicability of the compound to the assay of lactate dehydrogenase is described in comparison with a prevalent tetrazolium salt.