Melatonin: Occurrence and daily rhythm in Chenopodium rubrum

The occurrence of melatonin (5-methoxy-N-acetyltryptamine), a common animal hormone, in extracts of the above-ground parts of 15-day-old plants of Chenopodium rubrum was confirmed by liquid chromatography/tandem mass spectrometry. Using both this method and radioimmunoassay, changes in melatonin content during a 12 hr light/12 hr dark cycle were demonstrated. The melatonin concentration remained low or undetectable during the light period and increased during the darkness reaching a maximum at hours 4-6 of the dark period before rapidly decreasing. Both the nocturnal increase and the range of concentration are similar to those known in animals. Copyright (C) 1997 Elsevier Science Ltd.