Fluorescent behavior of melatonin and related indoleamines in natural deep eutectic solvents

Melatonin is a natural hormone produced by the pineal gland and generated as a special metabolite in plants from tryptophan as a precursor and serotonin as an intermediate. These indoleamines show intrin-sic fluorescence properties due to the presence of the indole group in their chemical structure, which made them suitable for the analysis by fluorescence-based techniques. In this research, it is described the first comprehensive study of the fluorescence of melatonin and its indole derivatives in several nat-ural deep eutectic solvents (NADES). As melatonin exhibits solvent-dependent fluorescence characteris-tics, we have measured the quantum yields of the molecules in NADES and conventional solvents with the purpose of understanding the fluorescent behavior in these solvents that will offer a new alternative to conventional medium. The results showed differential fluorescence behavior of melatonin and its metabolic precursors in NADES that could be explained in terms of each fluorophore structure and poten-tial hydrogen bond interactions with eutectic systems. Finally, the turn-off observed for melatonin in the NADES system based on fructose-citric acid and water could inspire the development of new analytical approaches.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

This research provides the first comprehensive study on the fluorescence characteristics of melatonin and its derivatives in natural deep eutectic solvents. The results show differential fluorescence behavior of melatonin and its metabolic precursors in these solvents, which could inspire the development of new analytical approaches.