All the isolated compounds were described for the first time from this species. Although inactive against 7 tested microorganisms (fungi, bacteria and yeast, human or plant pathogens), the raw extract was able to potentiate the effect of beta-lactam antibiotics on methicillin-resistant Staphylococcus aureus (MRSA), reducing the minimal inhibitory concentrations (MICs) by a factor of 2-32-fold. No synergy was found between the extract and streptomycin. From the five isolated compounds only jaseosidin 5 showed a moderate antimicrobial activity.

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The title compound [systematic name: 3,8-dihydr­oxy-3-(hydroxy­meth­yl)-9-methyl-6-methyl­enedeca­hydro­azuleno[4,5-b]furan-2(3H)-one], C15H22O5, is a sesquiterpene lactone showing the typical tricyclic guaianolide skeleton which has been isolated, together with other related metabolites, from the plant Centaurea musimomum. The present study confirms the mol­ecular structure, assigned by 1H NMR and MS spectroscopy, as well as the the 11β-hydroxy­methyl, 3β-hydr­oxy and 4α-methyl stereochemistry. The crystal structure is built through a network of O—H⋯O hydrogen bonds involving the three hydroxyl groups that are present in the mol­ecular skeleton.