Reduction of nitroblue tetrazolium to formazan by folic acid

The reduction of nitroblue tetrazolium (NBT) to formazan by folic acid, N-(4-aminobenzoyl) glutamic acid, and other amino acids was studied in this paper. The reduction involves only one of the two tetrazolium rings of NBT. The reaction is considerably more rapid with folic acid and N-(4-aminobenzoyl) glutamic acid than with the other amino acids under study. The electron donor moiety appears to be the carboxylic acid in the alpha position. N-ethyl-N'(3-dimethylaminopropyl)carbodiimide notably increases the rate of the reaction and promotes the reduction of both tetrazolium rings