THE TITLE COMPOUND [SYSTEMATIC NAME: 3,8-dihydr-oxy-3-(hydroxy-meth-yl)-9-methyl-6-methyl-enedeca-hydro-azuleno[4,5-b]furan-2(3H)-one], C(15)H(22)O(5), 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 mol-ecular structure, assigned by (1)H NMR and MS spectroscopy, as well as the the 11β-hydroxy-methyl, 3β-hydr-oxy 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 mol-ecular skeleton.