Cholinesterase inhibitors from leaves of Indian devil tree Alstonia scholaris L. R. Br.

Abstract

Four indole alkaloids were isolated from the alkaloid enriched (AE) extract of Alstonia scholaris L. R. Br. and their chemical structures were elucidated on the basis of NMR spectroscopic data compared with the previous research. These isolated alkaloids were identified as nareline ethyl ether (1), 19,20-(E)-vallesamine (2), 6,7-seco-19,20-epoxyangustilobine B (3) and 19,20-(E)-Akuammidine (4). All isolated compounds were evaluated their anti-cholinesterase and anti-amyloid aggregation activities. The concentrations to inhibit the acetylcholinesterase and butyrylcholinesterase activity by 50% (IC50) of alkaloids 1-4 were found to be similarly which were in the range of 0.25-0.41 mM and 0.26–0.43 mM, respectively. In addition, alkaloids 1-4 inhibited amyloid aggregation in the range of 29-33% and 35-43% at the final concentrations of 20 and 100 μM, respectively. Finally, the mixing alkaloids 1-4 significantly reduced accumulation of amyloid plaques observed from TEM images.