Galanthamine, is the most known Amaryllidaceae alkaloid, which is currently being prescribed for the treatment of mild to moderate Alzheimer's disease (AD) due to its anti-acetylcholinesterase activity. Narcissus L., a genus belonging to the same family, has been subjected to intensive research owing to its broad alkaloidal range.

The main objective of the present study was to evaluate Narcissus tazetta L. in terms of its therapeutic potential in AD and to isolate Amaryllidaceae alkaloids with anticholinesterase activity.

A qualitative determination of the alkaloidal contents of aerial parts and bulbs of the plant were carried out via Gas chromatography–mass spectroscopy (GC–MS) analysis. Additionally, secondary metabolites were isolated from the ethanolic extract of the plant by means of chromatographic methods. The structural elucidation of isolated compounds was established by spectroscopic techniques. Determination of acetylcholinesterase and butyrylcholinesterase inhibitory activities of the isolated Amaryllidaceae alkaloids were accomplished using a microplate assay modified from Ellman's method. These compounds were also subjected to docking studies to determine the non-covalent interactions formed with the active site residues of cholinesterase enzymes.

GC–MS monitoring on the profile of N. tazetta was resulted in the detection of 22 alkaloids. Isolation process on the plant has led to isolate four alkaloids belonging to three different skeleton types. Nuclear Magnetic Resonance (NMR) and MS findings verified that those compounds were identical with (−)-9-O-methylpseudolycorine, (−)-narcissidine, (−)-pancratinine-C and (+)-9-O-demethyl-2-α-hydroxyhomolycorine. Among those; 11-hydroxygalanthine and narcissidine have shown significant acetylcholinesterase (AChE) inhibitory activity based on our bioactivity results. It was observed that the docking scores were found close in general, when the docking scores of the isolated alkaloids calculated inside electric eel acetylcholinesterase (eeAChE) and Equus caballus butyrylcholinesterase (eqBuChE) were examined. Increased anti-acetylcholinesterase activity was observed in lycorine-type.

This is the first report on the isolation of (−)-pancratinine-C from the genus Narcissus. Docking scores of all the compounds isolated from the title plant were agreeable with the bioactivity results. The evaluation of the results given in this study, reveals that this particular Turkish Narcissus species represents a promising source of bioactive alkaloids with intriguing chemical structures which may have the potential to be drug leads.