The present study evaluates the gastroprotective properties of acetone extract, chloroform, and methanol fractions, alpha-spinasterol (1); 1,3-dihydroxy-7-methoxyxanthone (2); and 1,7-dihydroxy-2,3-methylenedioxyxanthone (3) obtained from Polygala cyparissias (Polygalaceae). Gastroprotective assays were performed in mice using ethanol/HCl and nonsteroidal anti-inflammatory drug (NSAID)/bethanechol-induced ulcer models. Chloroformic fraction showed no interesting results. On the other hand, in the ethanol/HCl-induced ulcer model, the treatment using doses of 50, 125, and 250 mg/kg promoted ulcer inhibition of 45.19+/-12.93%, 62.99+/-3.49%, and 67.40+/-4.75% for acetone extract and 43.70+/-5.12%, 64.56+/-5.64%, and 74.49+/-6.13% for methanol fraction. In the model of NSAID/bethanechol-induced ulcer, the ulcer inhibitions in the same doses were 28.12+/-12.45%, 60.16+/-6.58%, and 77.86+/-7.18% for the acetone extract and 46.09+/-6.92%, 67.45+/-4.36%, and 75.00+/-2.92% for the methanol fraction. In view of the antiulcer potential of the acetone extract and its high yield and xanthone content, it was submitted to chromatographic procedures, giving compounds 1-3, which were also evaluated in the ethanol-induced ulcer model. The results showed that at a dose of 50 mg/kg, these compounds reduced the percentage of ulcer by around 71.26+/-9.40%, 81.10+/-5.75%, and 86.22+/-3.42%, for compounds 1, 2, and 3, respectively. The antiulcerogenic activity of P. cyparissias may be attributed, at least in part, to these compounds.