In-vitro inhibition of human erythrocyte acetylcholinesterase by Salvia lavandulaefolia essential oil and constituent terpenes

Sage (Salvia spp) is reputed in European herbal encyclopaedias to enhance m emory, and current memory-enhancing/anti-dementia drugs are based on enhanc ing cholinergic activity by inhibiting cholinesterase. In this study the ef fects of Salvia lavandulaefolia Vahl. (Spanish sage) essential oil and some of its constituent terpenes on human erythrocyte acetylcholinesterase were examined in-vitro. The main constituents in the essential oil batch used f or analysis of cholinesterase inhibition were camphor (27%), 1,8-cineole (1 3%), alpha- and beta-pinene (10-15%) and bornyl acetate (10%) with other mi nor constituents (1% or less) including geraniol, limonene, linalool, terpi neol and gamma-terpinene. Using the Ellman spectrophotometric method, kinetic analysis was conducted on the interaction of the essential oil and the main monoterpenoids, campho r, 1,8-cineole and alpha-pinene. IC50 values were obtained for the essentia l oil, 1,8-cineole and alpha-pinene and were 0.03 mu g mL(-1), 0.67 mM and 0.63 mM, respectively. Camphor and other compounds tested (geraniol, linalo ol and gamma-terpinene) were less potent (camphor IC50: >10 mM). The essent ial oil, alpha-pinene, 1,8-cineole and camphor were found to be uncompetiti ve reversible inhibitors. These findings suggest that if the inhibitory activity of the essential oil is primarily due to the main inhibitory terpenoid constituents identified, there is a major synergistic effect among the constituents. Since no singl e constituent tested was particularly potent, it remains to be determined w hether these in-vitro cholinesterase inhibitory activities are relevant to in-vivo effects of the ingestion of S. lavandulaefolia essential oil on bra in acetylcholinesterase activity.