Melatonin is a naturally occurring hormone primarily secreted by the pineal gland. It regulates circadian rhythms, supporting healthy sleep-wake cycles. Additionally, it acts as a potent antioxidant, scavenging free radicals and reducing oxidative stress. Melatonin also modulates immune responses and exhibits anti-inflammatory properties. Its role in mitochondrial protection further contributes to cellular health.

Melatonin binds to MT1/MT2 receptors in the brain, synchronizing the body's internal clock with environmental light-dark cycles. It inhibits norepinephrine release in the hypothalamus, promoting sleep onset. As an antioxidant, it directly neutralizes ROS and upregulates endogenous antioxidant enzymes. Its lipophilic nature allows easy penetration into cells and mitochondria. Systemic effects include immune regulation and potential anti-tumor activity via apoptosis induction.