A quinolinemonocarboxylic acid that is quinoline-2-carboxylic acid substituted by hydroxy groups at C-4 and C-8. ChEBI: Xanthurenic acid is a quinolinemonocarboxylic acid that is quinoline-2-carboxylic acid substituted by hydroxy groups at C-4 and C-8. It has a role as a metabotropic glutamate receptor agonist, an iron chelator, a vesicular glutamate transport inhibitor and an animal metabolite. It is a quinolinemonocarboxylic acid and a dihydroxyquinoline. It is a conjugate acid of a xanthurenate.