Indigo carmine is an indigoid dye and a redox indicator.1,2 Upon reduction, indigo carmine shifts from blue to yellow with absorbance maxima of 610 and 407 nm, respectively.2 Formulations containing indigo carmine have been used as color additives in food and pharmaceutical preparations.
1.Claus, H., Faber, G., and K?nig, H.Redox-mediated decolorization of synthetic dyes by fungal laccasesAppl. Microbiol. Biotechnol.59(6)672-678(2002) 2.Tratnyek, P.G., Reilkoff, T.E., Lemon, A.W., et al.Visualizing redox chemistry: Probing environmental oxidation-reduction reactions with indicator dyesChem. Educator6(3)172-179(2001)