New Lycopodium Alkaloids Inhibiting Acetylcholinesterase

VALLEJO, M.G.; KEDIKIAN, V.G.; ORTEGA, M.G.; CABRERA, J.L; AGNESE, A.M.

San Pedro, Brasil

Conferencia; 2nd Brazilian Conference on Natural Products and XXVIII Annual Meeting on Micromolecular Evolution, Systematic and Ecology.; 2009

In our previous reports we demonstrated that alkaloid extract (AE) of Huperzia saururus (Lam.) Trevis. has an important inhibitory action on acetylcholinestarase (AChE) activity. Later, we assayed two purified alkaloids from this species, sauroxine and sauroine. Sauroxine showed an interesting inhibitory AChE activity (IC50=10.6 µg/mL). On the other hand, sauroine had not activity even at 500 µg/mL. The present study had the aim to identify other compounds responsible for the AE inhibitory action on AChE. We evaluated the effects for 6-hydroxy-lycopodine, the third majority alkaloid, and two new alkaloids, N-demethyl-sauroxine and Hidroxi-N-demethyl-sauroxine. N-demetil-sauroxine and 6-hidroxi-lycopodine were purified as it was described previously. Hidroxi-N-demetil-sauroxine was extracted from the plant material by means of alkaline extraction and purified through chromatographic techniques. Structural dilucidation of Hidroxi-N-demetil-sauroxine was achieved by GLC-MS and 1H and 13C, in1D and 2D NMR. Results sugget that this new alkaloid belongs to Lycopodium alkaloid group. AchE inhibitory action was evaluated by using an in vitro colorimetric method described by Ellman.  Concentrations assayed for the alkaloids were between 5 and 200 µg/mL. The IC50 values were calculated using Origin 6.0 software. Results show that the three alkaloids have an inhibitory action on the enzyme. Hydroxi-N-demethyl-sauroxine (IC50=26.3 ìg/mL) is a better inhibitor than N-demethyl-sauroxine (IC50=54.5 µg/mL) and 6-hydroxy-lycopodine (IC50=64,56 µg/mL). Nevertheless, sauroxine is herein the most effective inhibitor of the assayed alkaloids. Thus, new bioactive Lycopodium alkaloids with therapeutical aplication has been discovered. Further studies will make possible the understanding of the enzyme-compound interaction (REA).