Antioxidant Effect of Microwave-assisted Extracts of Olive Leaves on Sunflower Oil

Abstract

The antioxidant properties and total phenols’ content of 80% methanol, acetone and water extracts of olive leaves procured through Microwave Assisted Extraction (MAE) were examined. Two varieties of olive namely: Cronaiky and Roghani were the ones studied. Various experimental models were employed for antioxidant activity evaluation of the extracts. The results revealed the highest phenolic content (230.50 mg tannic acid equivalent g-1 extract) and the lowest IC50 in DPPH (86.81 µg ml-1 of extract), reducing power (166.45 µg ml-1 extract) and total antioxidant capacity (128.32 µg ml-1 of extract) indices were attributed to the methanol extract of Cronaiky variety. The efficacy of the extracts at three experimental levels (200, 500, 1,000 ppm) in blocking the oxidation process was investigated using peroxide value and thiobarbituric acid index for sunflower oil during its heating at 70°C (oven test method). The lowest peroxide value and thiobarbituric acid index was observed for the methanol extract of Cronaiky at its 1,000 ppm concentration. This extract was competitively comparable with BHA and BHT at either of the tested levels (100, 200 ppm). Thus, methanol extract of Cronaiky olive variety can be employed in place of synthetic antioxidants to establish oxidation stability in edible oils. Keywords: Antioxidant activity, Microwave, Olive leaf, Sunflower oil.