In our previous reports we demonstrated that alkaloid extract (AE) of Huperzia saururus (Lam.) Trevis has an important inhibitory action on acetylcholinestarase (AChE) activity1. Later, we assayed some majorities purified alkaloids from this species, sauroxine and sauroine2. Sauroxine showed an interesting inhibitory AChE activity (IC50=10.6 µg/mL). On the other hand, sauroine has not activity at 500 µg/mL.
The present study had the aim to identify other compounds responsibles for the AE inhibitory action on AChE. We evaluated the effects for 6-hidroxi-lycopodine, the third majority alkaloid, and two new alkaloids, N-demetil-sauroxine3 and Hidroxi-N-demetil-sauroxine. They are minor constituents in AE.
N-demetil-sauroxine and 6-hidroxi-lycopodine were purified as we described previously3,4. 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-ME and 1H and
AchE inhibitory action was evaluated by using an in vitro colorimetric method described by Ellman5. 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. Hidroxi-N-demetil-sauroxine (IC50=26.3 ìg/mL) is a better inhibitor than N-demetil-sauroxine (IC50=54.5 µg/mL) and 6-hidroxi-lycopodine (IC50=64,56 µg/mL). Nevertheless, sauroxine (CI50=10.6 µg/mL) is a more 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), as well as new assays with other alkaloids presents in AE.
