Merck, 199303-25G, Resazurin sodium salt

Resazurin is a small N-oxide derivative of dihydroxyphenoxazone. It is a non-ionic dye containing a small and planar chromophore. It is a redox indicator and changes from bluish violet through pink to colorless upon reduction. It is also used as a pH indicator for Ph 3.5 to 6.5 wherein it changed from orange to bluish violet. It is commercially available as resazurin sodium salt, which is also known as 3H-Phenoxazin-3-one, 7-hydroxy-, 10-oxide, sodium salt. It forms the red, fluorescent hydroxyphenoxazone resorufin on reduction and colorless hydroresorufin on further reduction.