Bioactivity-guided synthesis of gramine derivatives as new MT1 and 5-HT1A receptors agonists.

Twenty-four gramine derivatives were synthesized and evaluated on MT1 and 5-HT1A receptors in vitro. Among them, seven derivatives (7, 8, 16, 19, 20, 21, and 24) exhibited higher agonisting activities on MT1 or 5-HT1A receptors. Compared with gramine, derivatives 7, 8, 16, 19, 20, 21, and 24 displayed 1.6-3.5-fold increase in agonistic rates on 5-HT1A receptor. Particularly, derivatives 7, 19, and 21 exhibited significant agonistic activities on MT1 and 5-HT1A receptors with EC50 values of 0.51, 0.39, 0.50 mΜ and 0.28, 0.46, 0.23 mΜ, respectively. The preliminary structure-activity relationships of gramine derivatives were summarized for further investigation on MT1 and 5-HT1A receptors as new potential agonists.