Synthesis of a New Water-Soluble Melatonin Derivative with Low Toxicity and a Strong Effect on Sleep Aid

[Image: see text] A new melatonin sulfonate derivative sodium 4-(3-(2-acetamidoethyl)-5-methoxy-1H-indol-1-yl) butane-1-sulfonate (MLTBS) with higher water solubility (695 times) and lower cytotoxicity than natural melatonin (MLT) was synthesized, yet with the same sleep aid function. The poor solubility of MLT in water has been improved with a simple chemical reaction, which solves the poor solubility of melatonin in water, overcoming the safety problem caused by adding organic reagents such as dimethyl sulfoxide (DMSO) and ethanol to increase the solubility. Moreover, the modified MLT still has the same sleep aid effect as the natural MLT and higher biological safety. As a novel potential drug for sleep aid, the new MLT derivative could also flourish the application and research of this molecule in medicine and biology.