When exposed to light in a photosynthetic system, the dye is decolorised by chemical reduction.

As DCPIP is reduced and becomes colorless, the resultant increase in light transmittance can be measured using a spectrophotometer.

DCPIP can also be used as an indicator for vitamin C.[1][2] If vitamin C, which is a good reducing agent, is present, the blue dye, which turns pink in acid conditions, is reduced to a colorless compound by ascorbic acid.

The end point is a pink color that persists for 10 seconds or more, if there is not enough ascorbic acid to reduce all of the DCPIPH.

Pharmacological experiments suggest that DCPIP may serve as a pro-oxidant chemotherapeutic targeting human cancer cells in an animal model of human melanoma; DCPIP-induced cancer cell death occurs by depletion of intracellular glutathione and upregulation of oxidative stress.