SMILES: C1=CC2=C(C=C1S(=O)(=O)O)C(=C(N2)C3=NC4=C(C3=O)C=C(C=C4)S(=O)(=O)O)O
Description: The molecule is a member of the class of indolones obtained by formal 2,2'-oxidative coupling of two molecules of 3-oxo-2,3-dihydroindole-5-sulfonic acids. It has a role as a food colouring and a histological dye. It is a member of indolones, an olefinic compound, an enone, an arenesulfonic acid and a ring assembly. It is a conjugate acid of an indigo carmine(2-).