Indole alkaloids from Tabernaemontana australis (Müell. Arg) Miers that inhibit acetylcholinesterase enzyme

Ten indole alkaloids from the chloroform extract of stalk of Tabernaemontana australis (Müell. Arg) Miers were tentatively identified by GC–MS, viz., coronaridine (1), voacangine (2), voacangine hydroxyindolenine (3), rupicoline (4), ibogamine (5), ibogaine (6), ibogaline (7), desethyl-voacangine (8), voachalotine (9), and affinisine (10). Of these, the first four were isolated by silica gel open column chromatography, identified by uni- and bidimensional NMR, IR, MS and showed anti-cholinesterasic activity at the same concentration as the reference compounds physostigmine and galanthamine (detection limit of 0.01 mM) by TLC assay using the modified Ellman’s method.

In an enzymatic TLC survey, among the 10 alkaloids identified in Tabernaemontana australis, 1–4 inhibited the acetylcholinesterase enzyme at the same detection limit concentration of the reference compounds physostigmine and galanthamine, showing that iboga alkaloids are promising anti-Alzheimer agents.Figure optionsDownload as PowerPoint slide