Grosso, ClaraDelerue-Matos, CristinaMeinedo, Ana Catarina Venâncio2026-02-252026-02-252025-11-17http://hdl.handle.net/10400.22/31892Melatonin is an indolamine produced in both animals and plants, playing a central role in regulating the sleep–wake cycle and recognized for its antioxidant properties. The discovery of melatonin in plants, called phytomelatonin, has enabled its use in dietary supplements, where it offers a natural alternative to the synthetic form. However, phytomelatonin is present in very low concentrations, making it necessary to find plant matrices richer in melatonin and optimize its extraction process to develop an effective dietary supplement for sleep regulation. In this study, eight plant matrices — chamomile, goji berries, passionflower, walnut, valerian, black pepper, lavender, and decaffeinated coffee — were selected, and five extraction solvents (ethanol, methanol, ethyl acetate, chloroform, and diethyl ether) were tested. Extraction was performed by ultrasound-assisted extractions, and the presence/absence of melatonin was analysed by HPLC-FLDDAD. The presence of melatonin was detected in four matrices: walnut, lavender, passionflower, and valerian, and the best extraction solvents were methanol and ethanol. Walnut extracts showed the highest extraction yields; however, the melatonin content was below the limit of quantification. Mixtures of matrices revealed promising, increasing melatonin content compared to individual extractions, particularly when walnut, passionflower, valerian, and lavender were combined.engMelatoninPhytomelatoninSleep disordersDietary/ food supplementsExtractionmaster thesis204178908