Inducible heme oxygenase (HO)-1 is known to play a major role in the pathogenesis of several diseases, and it protects cells against oxidant-mediated injury. The bioassay-guided fractionation of the EtOH extract of the flowered fruit-spike of Prunella vulgaris L. (Labiatae) yielded two ursane-type triterpenes, 3beta,23-dihydroxyurs-12-en-28-oic acid (23-hydroxyursolic acid) (1) and 3beta-hydroxyurs-12-en-28-oic acid (ursolic acid) (2). Western blotting demonstrated that treatment with compound 1 increased the expression of HO-1 in a dose-dependent manner in human liver-derived HepG2 cells. Investigation of structure-related HO-1 inducing activity suggested that the hydroxyl group at the C-23 position in the ursane skeleton is important for this activity.