Pleurotus ostreatus (P.o.)oyster mushroom, is widely used immunomodulatory nutritional supplement P.o. and pleuran (ß-1,3/1,6 glucan from P. o.) have been shown not only to exchange the defence against infections, but also to lower cholesterol, to have antitumor, anticoagulant, anti-inflammatory, antinociceptive and hepatoprotective properties. Recently, the research has focused on their antioxidant properties.