We presented a marine natural product, norsiphonarienone, isolated from Siphonaria lessoni, a pulmonate limpet of Central Chile. The norsiphonarienone was pharmacologically studied in rat thoracic aorta with endothelium previously contracted with phenylephrine. This technique has been widely used to describe pharmacological characterization and seek for mechanisms of action of natural products and other physiological phenomena. The main characteristics described are pD₂ (-log EC₅₀) and maximum effect or maximal contraction (E_max). The results show that norsiphonarienone induced a significant difference in the maximal contraction and also in the pD₂ (-log EC₅₀).

Key words: Norsiphonarienone, Pharmacological study, Rat thoracic aorta, Siphonaria lessoni