Melatonin-d4 is deuterium labeled Melatonin. Melatonin is a hormone made by the pineal gland that can activates melatonin receptor. Antioxidative and anti-inflammatory properties[1][2][3]. Melatonin is a selective ATF-6 inhibitor and induces human hepatoma cell apoptosis through COX-2 downregulation[4].