Artemisinin 1, dihydro-epideoxyarteannuin B 2 and deoxyartemisinin 3 were isolated from the sequiterpene lactone-enriched fraction obtained from the crude ethanolic extract of Artemisia annua L. These compounds were tested on ethanol and indomethacin-induced ulcer models. Compound 1 did not afford cytoprotection under the experimental models tested. Only compounds 2 and 3 decreased the ulcerative lesion index produced by ethanol and indomethacin in rats. These compounds did not demonstrate antiulcerogenic activity when tested on the ethanol-induced ulcer model, with previous administration of indomethacin, suggesting that the antiulcerogenic activity is a consequence of prostaglandin synthesis increase.68515-8