Determination of melatonin content in traditional Thai herbal remedies used as sleeping aids

Background: Melatonin content was screened in leaves of seven edible herbs used as sleeping aids in Thai traditional medicine. These plants are Piper nigrum L, Sesbania glandiflora (L.) Desv., Sesbania sesban (L.) Merr., Senna tora (L.) Roxb., Moringa oleifera Lam., Momordica charantia L. and Baccaurea ramiflora Lour. Dried leaves were extracted by sonication in methanol for six hours at room temperature, and then melatonin was purified by C18 solid phase extraction (SPE). Melatonin was then quantified by a validated RP-C18 HPLC method with fluorescent detection. Findings: Melatonin contents in extracts of B. ramiflora, S. glandiflora, M. charantia, S. tora and S. sesban were 43.2, 26.3, 21.4, 10.5 and 8.7 ng/g of dry sample weight, respectively. The highest melatonin content was from P. nigrum extract (1092.7 ng/g of dry sample weight). Melatonin was not detected in the extract of M. oleifera. Melatonin identification was confirmed by ELISA. Conclusions: Melatonin was found in six of the seven herbs in the traditional Thai sleeping recipe. One of these, P. nigrum, exhibited an encouragingly high amount of melatonin.