Four new mulinane-type diterpenoids besides the known compounds mulin-11,13-dien-20-oic acid, 13α-hydroxyazorellane, 13β- hydroxyazorellane, mulinolic acid, azorellanol, and mulin-11,13-dien-18-acetoxy- 16,20-dioic acid were isolated from the Chilean plant Azorella trifurcata. One of the new metabolites isolated, 7α-acetoxy-9-epi-13β- hydroxymulinane, possesses a new trans-syn-trans arrangement in a tricyclic ring system not previously encountered in nature. Among the mulinane diterpenoids isolated, mulin-11,13-dien-20-oic acid showed the gastroprotective effect on HCl-EtOH-induced gastric lesions in mice (ED50 = 55 mg kg -1). Regarding the mode of gastroprotective action for this active compound, its effect was reduced by pre-treatment of the mice with indomethacin and N-ethylmaleimide, suggesting that prostaglandins and sulfhydryl compounds are positively involved in the gastroprotective activity using this model. © the Partner Organisations 2014.