Identification of melatonin in plants and its effects on plasma melatonin levels and binding to melatonin receptors in vertebrates.

TLDR

Melatonin, previously thought exclusive to animals, was detected in 24 edible plants. The authors identified melatonin by radioimmunoassay and confirmed it with HPLC‑fluorescence. Plant‑derived melatonin varied widely, was highest in rice family, increased blood levels in chicks, inhibited radiolabeled melatonin binding in rabbit brain, demonstrating that dietary melatonin enters circulation and can bind mammalian brain receptors.

Abstract

Twenty-four edible plants were investigated for the presence of melatonin, heretofore considered to be a molecule found only in the animal kingdom. The amount of melatonin in different plants varied greatly with highest melatonin being present in plants of the rice family. Melatonin was identified by radioimmunoassay and verified by high performance liquid chromatography with fluorescence detection. Feeding a diet containing plant products rich in melatonin to chicks increased radioimmunoassayable levels of melatonin in their blood. Likewise, melatonin extracted from plants inhibited binding of [125I]iodomelatonin to rabbit brain. Thus, melatonin ingested in foodstuffs enters the blood and is capable of binding to melatonin binding sites in the brain of mammals.