Quinolinic acid is a dicarboxylic acid with a pyridine backbone. It may be prepared by the oxidation of quinoline.Quinolinic acid is a downstream product of the kynurenine pathway, which metabolizes the amino acid tryptophan. It acts as an NMDA receptor agonist. Quinolinic acid has a potent neurotoxic effect. Studies have demonstrated that quinolinic acid may be involved in many psychiatric disorders, neurodegenerative processes in the brain, as well as other disorders. Within the brain, quinolinic acid is only produced by activated microglia and macrophages. Quinolinic acid is a byproduct of the kynurenine pathway, which is responsible for catabolism of tryptophan in mammals. Quinolinic acid is unable to pass through the blood-brain barrier (BBB) and must be produced within the brain microglial cells or macrophages that have passed the BBB.