Alkaloids from the club moss Lycopodium annotinum L. – acetylcholinesterase inhibitory activity in vitro

Plant species belonging to the genera Lycopodium are known to produce so-called Lycopodium alkaloids. The club moss Huperzia serrata (Thumb.) Trev., which has long been used traditionally against Alzheimer's disease in China, has been shown to contain Lycopodium alkaloids which are acetylcholinesterase inhibitors [1].

Five species of club mosses are found in Iceland. Huperzia selago L. Bernh. ex Schrank & C. Martius has previously been studied and shown to contain a new alkaloid, selagoline, in addition to the known huperzine A and serratidine. The inhibitory activity on acetylcholinesterase was not investigated [2]. The aim of this study was to examine the alkaloid content of the Icelandic Lycopodium annotinum and to determine their ability to inhibit the enzyme acetylcholinesterase in vitro.

The plant extract was fractionated and the alkaloids purified using liquid chromatography methods (VLC, SPE, HPLC) and ¹H- and ¹³C-NMR spectroscopy was used for the structure determination. The inhibitory activity of the alkaloids towards acetylcholinesterase was determined by an in vitro TLC acetylcholinesterase assay [3].

Three Lycopodium alkaloids from L. annotinum were found to inhibit acetylcholinesterase activity in vitro including the known annotine. Another known alkaloid from this plant, annotinine, did not show inhibition. Annotine and annotinine have only been found in L. annotinum and their effect on acetylcholinesterase has not been described before.

References: 1. Ma, X.Q. et al. (2004), Nat. Prod. Rep. 21: 752–772. 2. Staerk, D. et al. (2004), Nat. Prod. Res. 18: 197–203. 3. Rhee I.K. et al. (2001), J. Chromatogr. A 915: 217–223.