Anxiolytic effect of natural galphimines from Galphimia glauca and their chemical derivatives

The anxiolytic effects of galphimine B (1), galphimine A (2), and galphimine E (3), natural nor-secofriedelanes isolated from Galphimia glauca, as well as derivatives obtained by acetylation (4), hydrogenation of the C-1/C-2 double bond (5), basic hydrolysis followed by hydrogenation of the C-1/C-2 double bond (6), and deacetylation (7) of galphimine E (3), were evaluated on ICR mice exposed to the elevated plus-maze test. This study also included the evaluation of a galphimines-rich fraction (GRF) with a known concentration of 1-3, obtained from the dry leaves of G. glauca. Intraperitoneal administration of 15 mg/kg of 1, 2, 6, and GRF (1 h before testing) caused an anxiolytic-like effect in the animals, increasing significantly (p <0.001) the percentage of time of permanence and the number of crossings toward the open arms of the plus-maze. No activity was detected after administration of compounds 3, 4, 5, and 7. These results showed that GRF had activity similar to the most active pure galphimines (1 and 2) and that, like for the spasmolytic activity previously reported, the main determining factor responsible for the anxiolytic activity of the compounds was the presence of free hydroxyl groups at C-4, C-6, and C-7 and the presence of the double bond in the A ring.