Analgesic effect of leaf extract from Ageratina glabrata in the hot plate test

Ageratina glabrata (Kunth) R.M. King & H.Rob., Asteraceae (syn. Eupatorium glabratum Kunth) is widely distributed throughout Mexico and popularly known as "chamizo blanco" and "hierba del golpe" for its traditional use as external analgesic remedy. Though glabrata species has been chemically studied, there are no experimentally asserted reports about possible analgesic effects which can be inferred from its genus Ageratina. To fill the gap, we evaluated A. glabrata extracts in an animal model of nociception exploiting thermal stimuli. NMR and mass analyses identified a new thymol derivative, 10-benzoiloxy-6,8,9-trihydroxy-thymol isobutyrate (1), which was computationally converted into a ring-closed structure to explain interaction with the COX-2 enzyme in a ligand-receptor docking study. The resulting docked pose is in line with reported crystal complexes of COX-2 with chromene ligands. Based on the present results of dichloromethane extracts from its dried leaves, it is safe to utter that the plant possesses analgesic effects in animal tests which are mediated through inhibition of COX-2 enzyme.