Nitroblue tetrazolium chloride;NBT

 2,2'-bis(4-Nitrophenyl)-5,5'-diphenyl-3,3'-(3,3'-dimethoxy-4,4'-diphenylene)ditetrazolium chloride;

 Nitrotetrazolium blue chloride

Nitro Blue Tetrazolium (NBT) is a chromogenic substrate that, like other tetrazolium compounds, can be reduced to produce a colored formazan derivative. It is used in the “NBT test” to evaluate the activity of NADPH oxidase in phagocytes, which results in the production of blue reduced NBT formazan in normal cells but not in those from patients with chronic granulomatous disease. NBT can also be used as a chromogenic activity stain for oxidoreductases in gels or solutions. More commonly NBT is often paired with 5-bromo-4-chloro-3-inolyl phosphate (PCIB) for the colorimetric detection of alkaline phosphatase activity. Alkaline phosphate converts PCIB to a product that reduces NBT to its formazan derivative, resulting in a black-purple precipitate.Chromogenic substrate; competitive inhibitor of NOS