Antioxidant properties of plant extracts are apparently related to the content of their phenolic compounds. In this study, phenolic compounds from two acorns varieties namely Q.branti var persica (Q.b) and Q.castaneifolia var castaneifolia (Q.c) were extracted with methanol (80%). After evaporation with rotary evaporator, extracts were dried with freeze drier. The concentrations of phenolic compounds in the extracts were determined according to the Folin-Ciocalteu method, and results were expressed as tannic acid equivalents per gram of dried extract (TAE/g d.e). Castaneifolia variety had the highest phenolic content with 217.65 (TAE/g d.e). Antioxidant activity of methanolic extracts were studied in sunflower oil and compared with synthetic antioxidants, by measuring their peroxide and thiobarbituric acid values during accelerated storage. Methanolic extracts of acorns at three different concentrations (250,500 and 1000 ppm) and synthetic antioxidant at two concentrations were added to sunflower oil. Both extracts retarded the oxidation of sunflower oil at 70°c more efficiently than BHA and BHT. The peroxide and thiobarbitoric acid values of control samles were raised to 328.88 (meq peroxide/ kg oil) and 0.58 (mg malon aldehyde/kg oil) after tewelve days storage while this values were 176.36 and 0.332 for oil sample contain 1000 ppm methanilic extract of Q.c  and 183.2 and for Q.b were 0.374, respectively.

Keywords: Antioxidant activity, Key Words: Acorn fruit, Sunflower oil, methanolic extract

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