8-hydroxy-9-keto-10αH-eremophil-7(11)-en-8,12-olide Isolated from the Essential Oil of Senecio filaginoides DC and its Antimicrobial Activity

Background: The genus Senecio (Asteraceae) is widely distributed all over the world (except in Antarctica and Amazonas) and includes more than 3000 species. Senecio filaginoides DC, one of the 270 species which occur in Argentina, grows from Jujuy to Santa Cruz provinces, also called Charcao, is a native species that grows spontaneously near Comodoro Rivadavia, Chubut Province, in the southeast of Argentina.Its small white flowers gather in bundles at the end of the branches. By the end of November at flowering, it concentrates a great number of insects. Methods: To better understand the chemistry of this plant and identify taxonomic markers, in the present study, we isolated a terpenoid from this genus and characterized a sesquiterpene with eremophilenolide skeleton from the fresh aerial parts of S. filaginoides. The structure of this compound was elucidated mainly by advanced NMR experiments, including inverse techniques such us, HSQC, HMBC, COSY and NOESY. The essential oil and the isolated compound, 8-hydroxy-9- keto-10αH-eremophil-7(11)-en-8,12-olide, were tested for their antimicrobial activities. Results: In the present study, P. aeruginosa strains were highly susceptible to the dilutions from 1/125 to 1/1000, whereas S. aureus showed sensitivity to two dilutions tested: 1/125 and 1/250.All species of Candida sp had biological activity from dilutions: 1/125 and 1/2000. Conclusion: The compound isolated was active against E. coli and P. aeruginosa with a MIC of 250 μg/mL, and active against E.faecalis with a value of 100 μg/mL. This is the first report about eremophilane isolated from the essential oil species of Senecio from East Central Area of Patagonia.