Indican

Indican is a colourless organic compound, soluble in water, naturally occurring in Indigofera plants. It is a precursor of indigo dye.

Indican is a glycoside. Its hydrolysis yields β-D-glucose and indoxyl. Reaction of indoxyl by a mild oxidizing agent, eg. atmospheric oxygen, yields indigo dye. Such a reaction is seen in individuals affected by the blue diaper syndrome, who exhibit a defect in tryptophan metabolism. Tryptophan is first converted to indole, then to indican by bacteria in the gut. Indican is then excreted into the urine and from there into the diaper where, upon exposure to air, it is converted to indigo blue dye.