Reyes, M.; Schmeda-Hirschmann, G.; Razmilic, I. Laboratorio de Productos Naturales, Instituto de Química de Recursos Naturales, Universidad de Talca, Casilla 747, Talca, Chile. Theoduloz, C.; Yáñez, T.; Rodríguez, J. Departamento de Ciencias Básicas Biomédicas, Facultad de Ciencias de la Salud, Universidad de Talca, Casilla 747, Talca, Chile.An infusion or decoction of the aerial parts of Fabiana imbricata (Solanaceae) is used in traditional medicine in Chile and Argentina as a digestive and diuretic agent. The main sesquiterpene of the plant was identified as 11-hydroxy-4-amorphen-15-oic acid. At doses of 25, 50 and 100 mg/kg, the compound showed a dose-dependent gastroprotective effect in HCl/EtOH-induced gastric lesions in mice reducing the lesions by 68% at 100 mg/kg. Seven derivatives of the terpene were prepared and their gastroprotective effect was assessed in HCl/EtOH-induced gastric lesions in mice. The cytotoxicity of the products was evaluated in fibroblasts and AGS cells. At 100 mg/kg, 11-hydroxy-4-amorphen-15-p-toluidinamide presented the best gastroprotective effect reducing the gastric lesions by 80%, showing a similar effect to lansoprazole at 20 mg/kg. The compound, however, presented higher cytotoxicity than other derivatives with the IC50 ranging between 110 and 145 µm in AGS cells and fibroblasts, respectively. Most compounds proved to be non-toxic showing cytotoxicity values higher than 1000 µm. The spectroscopic data of six 11-hydroxy-4-amorphen-15-oic acid derivatives are presented here for the first time.