Synthesis and the biological activity of new melatonin dimeric derivatives

A new series of melatonin (MLT) dimers were obtained by linking together two melatonin units with a linear alkyl chain through the MLT acetamido group or through a C-2 carboxyalkyl function. The binding properties of these ligands were evaluated in in vivo experiments on cloned human MT1 and MT2 receptors expressed in NIH3T3 rat fibroblast cells. The class of 2-carboxyalkyl dimers was the most interesting one with compounds having good MT1/MT2 nanomolar affinity. The data obtained suggest that the spacer length is crucial for optimal interaction at both receptor subtypes as well as to determine functional activity of the resulting dimers.