Abstract: The aim of our study was to evaluate the biological value of methanolic extracts obtained from Pleurotus ostreatus fruiting bodies cultivated in a traditional household. We used four substrate formulas containing wheat straw, borceag straw (borceag is a vetch and oat mixture used for animal nutrition) and beech shavings in order to determine the substrate influence on the content of antioxidant compounds and on the antioxidant potential of brute extracts. The antioxidant potential was determined using free radical scavenging activity (ABTS, DPPH and superoxide radicals), inhibition of lipid peroxidation, reducing power and chelating activity. Virtually, we observed that the presence of an increased lignin component (beech shavings) in substrates reduces the number of some biological active molecules. This fact was directly linked to a decreased biological activity. These results showed that, depending on how easily the substrate is decomposed by mycelium and the quantity on nutrients assimilated by it, the nutritional value of the obtained mushrooms will increase.