formazan

A water-insoluble colored compound of the general structure, RNH—N=CR′—N=NR″, formed by reduction of a tetrazolium salt in the histochemical demonstration of oxidative enzymes; the R's are usually phenyl groups; examples include neotetrazolium, blue tetrazolium, and nitro blue tetrazolium.

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form·a·zan 'fȯr-mə-.zan n a hypothetical hydrazone CH₄N₄ related to formic acid and known only in the form of intensely colored derivatives of which some are obtained from colorless compounds by the reducing action of living tissues and serve as indicators of viability by color production also any of these derivatives

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for·ma·zan (forґmə-zan) reduced nitroblue tetrazolium that is dark blue and water-insoluble; the reduction process is the basis of the nitroblue tetrazolium test (see under test).