Monoterpene indole alkaloids from Vinca minor L. (Apocynaceae): Identification of new structural scaffold for treatment of Alzheimer's disease
Rudolf Vrabec, Jana Maříková, Miroslav Ločárek, Jan Korábečný, Daniela Hulcová, Anna Hošťálková, Jiřı́ Kuneš, Jakub Chlebek, Tomáš Kučera, Martina Hrabinová, Daniel Jun, Ondřej Soukup, Vincenza Andrisano, Jaroslav Jenčo, Marcela Šafratová, Lucie Nováková, Lubomı́r Opletal, Lucie Cahlíková
Abstract
One undescribed indole alkaloid together with twenty-two known compounds have been isolated from aerial parts of Vinca minor L. (Apocynaceae). The chemical structures of the isolated alkaloids were determined by a combination of MS, HRMS, 1D, and 2D NMR techniques, and by comparison with literature data. The NMR data of several alkaloids have been revised, corrected, and missing data have been supplemented. Alkaloids isolated in sufficient quantity were screened for their in vitro acetylcholinesterase (AChE; E.C. 3.1.1.7) and butyrylcholinesterase (BuChE; E.C. 3.1.1.8) inhibitory activity. Selected compounds were also evaluated for prolyl oligopeptidase (POP; E.C. 3.4.21.26), and glycogen synthase 3β-kinase (GSK-3β; E.C. 2.7.11.26) inhibition potential. Significant hBuChE inhibition activity has been shown by (−)-2-ethyl-3[2-(3-ethylpiperidinyl)-ethyl]-1H-indole with an IC50 value of 0.65 ± 0.16 μM. This compound was further studied by enzyme kinetics, along with in silico techniques, to reveal the mode of inhibition. This compound is also predicted to cross the blood-brain barrier (BBB) through passive diffusion.