Human pathological metabolites

3,4-Methylenedioxyamphetamine (MDA) is an entactogen, stimulant, and psychedelic drug of the amphetamine and MDxx families that is encountered mainly as a recreational drug. It is usually taken orally.

MPP+ (1-methyl-4-phenylpyridinium) or cyperquat is a positively charged organic molecule with the chemical formula C12H12N+. It is a monoaminergic neurotoxin that acts by interfering with oxidative phosphorylation in mitochondria by inhibiting complex I, leading to the depletion of ATP and eventual cell death.

Norsalsolinol is a tetrahydroisoquinoline that is produced naturally in the body through the metabolism of dopamine. It has been shown to be a selective dopaminergic neurotoxin, and has been suggested as a possible cause of neurodegenerative conditions such as Parkinson's disease and the brain damage associated with alcoholism, although evidence for a causal relationship is unclear.

Cysteinyldopa, or '5-S-cysteinyldopa', is a catecholamine. Excessive cysteinyldopa in plasma and urine has been linked to melanoma. Cysteinyldopa is found in large amounts in the plasma and urine of patients with melanoma. It is therefore used in the diagnosis of melanoma and for the detection of postoperative metastases. Cysteinyldopa is believed to be formed by the rapid enzymatic hydrolysis of 5-S-glutathionedopa found in melanin-producing cells.

α-Methyldopamine (α-Me-DA), also known as 3,4-dihydroxyamphetamine (3,4-DHA or HHA) or as catecholamphetamine, is a research chemical of the catecholamine and amphetamine families. It is a monoamine releasing agent and a metabolite of MDMA and MDA. The bis-glutathionyl metabolite of α-methyldopamine is slightly neurotoxic when directly injected into the brain's ventricles.