AMK is an active metabolite of the neurohormone melatonin . It is formed from melatonin via the metabolic intermediate AFMK that is then deformylated by catalase or formamidase. AMK scavenges singlet oxygen in vitro when used at a concentration of 200 µM. It inhibits the epinephrine- and arachidonic acid-induced production of prostaglandin E2 and PGD2 in ovine seminal vesicle microsomes in a concentration- and time-dependent manner, as well as LPS-induced increases in COX-2 levels in RAW 264.7 macrophages when used at a concentration of 500 µM. AMK (20 mg/kg) decreases MPTP-induced increases in lipid peroxidation in the cytosol and mitochondria from substantia nigra and striatum in a mouse model of MPTP-induced Parkinson’s disease.