3-Indoxyl phosphate (sodium)

3-Indoxyl phosphate (3-IP) is a chromogenic and electrochemical substrate for alkaline phosphatase. Upon enzymatic cleavage by alkaline phosphatase, 3-indoxyl is released and subsequently oxidized to produce water-insoluble indigo, which can be quantified by colorimetric detection at 660 nm as a measure of alkaline phosphatase activity. 3-Indoxyl phosphate can also be converted to water-soluble leucoindigo by reduction of indigo in alkaline solution by sodium dithionite, which can be quantified by colorimetric detection at 415 nm or voltametric detection as a measure of alkaline phosphatase activity.2 3-Indoxyl phosphate has been used in ELISAs.