Uncarialins A-I, Monoterpenoid Indole Alkaloids from Uncaria rhynchophylla as Natural Agonists of the 5-HT 1A Receptor.

Nine new monoterpenoid indole alkaloids, uncarialins A-I ( 1 - 9 ), were isolated from Uncaria rhynchophylla as well as 14 known analogues ( 10 - 23 ). Their structures were determined by HRESIMS, 1D and 2D NMR, and experimental and calculated electronic circular dichroism data. Compounds 5 , 7 , 15 , and 22 displayed significant agonistic effects against the 5-HT _1A receptor with EC ₅₀ values of 2.2 ± 0.1, 0.1 ± 0.1, 1.6 ± 0.3, and 2.0 ± 0.5 μM, respectively. The mechanisms of action of these four compounds with the 5-HT _1A receptor were investigated by molecular docking, and the results suggested that amino acid residues Asp116, Thr196, Asn386, and Tyr390 played critical roles in the observed activity of the above-mentioned compounds.