Glaucacetalin E and galphimidin B from Galphimia glauca and their anxiolytic activity

Abstract

Ethnopharmacological relevance: Galphimia glauca is a Mexican medicinal plant used to treat anxiety, fear, phobia and stress as it possesses sedative properties which produce a calming effect. Although some chemical and pharmacological studies have already been carried out on G. glauca, there are still new chemical entities from this plant whose anxiolytic activity should be established.

Aim of the study: To validate the use of G. glauca growing in Cuernavaca, Morelos, as an anti-stress agent, through the purification and structural identification of its extracts' chemical constituents; the analysis of the biogenetic relationship of its chemical compounds, and its biological evaluation to demonstrate its traditional use as anxiolytic agents.

Materials and methods: The structures of all isolated compounds were established based on their spectroscopic and spectrometric data. The structure of compound 2 was corroborated through X-Ray. The anxiolytic and sedative-like activities were assessed by the open-field, hole-board and exploration cylinder test.

Results: The nor-triterpenes glaucacetalin E (1) and galphimidin B (2) were isolated for the first time along with seven other known compounds, one of them galphimidin (3), from the CHCl₃ fraction of the aerial parts of Galphimia glauca. The biogenesis of the natural nor-triterpenes isolated from Galphimia glauca is delineated for the first time starting from the taraxasteryl cation. Oral administration of CHCl₃ fraction and 1-3 compounds produced significant attenuation in the anxiety-response in cylinder activity, decrease in the ambulatory activity and in head dipping when compared to the vehicle. However, only the extract enhanced the pentobarbital-induced hypnosis. Diazepam was used as a positive control.

Conclusion: Our results suggest that G. glauca growing in Cuernavaca, Morelos, exerts anxiolytic-like activity due to the presence of the nor-triterpenes 1-3. These results reinforce the potential use of this species in the treatment of anxiety.

Keywords: Anxiolytic activity; Biogenesis; Galphimia glauca; Galphimidin B; Glaucacetalin E; Malpighiaceae; Sedative effect.