Stability of melatonin in eutectic systems: New avenues in therapeutic product development

Melatonin is an indoleamine with functions as neurohormone, that is well known as pharmaceutical or healthcare product. Like many pharmaceutical compounds, melatonin is recognized to be an unstable molecule, principally sensitive to light and high temperatures. Storage conditions, including temperature and light, over different storage periods have been considered as important factors in melatonin degradation. This research describes for the first time, the utilization of natural deep eutectic solvents (NADES) as green alternatives to organic solvents for improving the stability of the hormone under various storage conditions. The results showed that temperature and light effect on melatonin content during the storage presented a diverse behavior according to the solvent. At low temperatures, the hydrophilic eutectic systems based on choline chloride-glycerol and lactic acid-glucose, along with water, were the most effective in extending the shelf life of the hormone compared to conventional solvents. However, at high temperature, this behavior was reversed. Regarding the effect of light, it significantly affects the stability of melatonin, primarily UV exposure. The eutectic systems appear to be the best medium for melatonin stability under this condition. These findings highlight the potential of NADES for their protective role in the stability of the compound that could be explained in terms of their viscosity and the hydrogen bond interactions within the solute and the eutectic systems.