Plants constitute an important source of active natural products which differ in terms of structure and biological properties. In recent years, the prevention of cancer and cardiovascular diseases has been associated with the ingestion of fresh fruits, vegetables or teas rich in natural antioxidants. In this work, Brazilian plants extracts of Polygala paniculata (PP), Hyptis fasciculata (HF), Orbygnia speciosa (OS) and a flavonoid isolated from Hyptis fasciculata known as isoquercetin (IQ) were evaluated for their capacity to protect Saccharomyces cerevisiae cells, an eukaryotic cell model, against the lethal oxidative stress caused by hydrogen peroxide and menadione (superoxide radical generator). During the experiments, first exponencial cells were treated with 5 mg/mL of extracts or 10 mg/mL of isoquercetin for 1 hour at 28°C. Thereafter, cells were exposed to 2 mM peroxide or 30 mM menadione for 1 hour at 28°C. Only the extracts of Polygala paniculata and almonds of Orbygnia speciosa were not able of increasing tolerance to peroxide, however these extracts produced an increase in survival rates after menadione stress. The protective effect of HF and IQ against oxidative damage produced by both peroxide and menadione seems to be correlated with decrease in lipid peroxidation levels, thus making it possible to consider these plants as a potential sources of antioxidants that protect lipids against oxidation.