GC-MS analysis of volatiles from different Lycopodium species with acetylcholinesterase activity

Abstract

Searching for natural inhibitors of different enzymes, e.g. acetylcholinesterase (AChE), is a modern approach in drug discovery. Lycopodium L. (Lycopodiaceae) species containing alkaloids appear to be a rich source of acetylcholinesterase inhibitors.

                In our study, a GC-MS analysis of the extracts of L. clavatum, L. annotinum, and Huperzia serrata (syn. Lycopodium serratum Thunb.), containing volatile constituents with AChE-inhibitory activity, was performed. The detection of AChE-inhibitory activity of the investigated extracts was achieved by TLC-bioautography.

                The GC-MS analysis was carried out on a Shimadzu GC-2010 Plus chromatograph coupled to a QP2010 Ultra mass spectrometric detector using a Phenomenex capillary column ZB-5MS (30 m; diameter of 0.25 mm and thickness of 0.25 µm). The initial column temperature was set to 50 °C, which was held for 3 min, and in the next step, the column was heated to 250 °C at a rate of 8 °C per min (and was then held at that temperature for 2 min). The split ratio after the injection of 1 µL was 1:20 and helium was used as the carrier gas (the flow rate was 1 mL per min). Ionization was performed by electron impact at 70 eV. The identification of compounds was based on a comparison of their mass spectra with those of MassFinder and NIST mass spectral libraries, as well as by retention index (calculated based on a homologous series of n-alkanes) comparison.

                The GC-MS analysis allowed the identification of alkaloids belonging to the main classes of alkaloids characteristic for Lycopodium spp., e.g. the lycopodane group.