Evaluation of Antioxidant Activity of Some Natural Extracts and Propyl Gallate in Refined Palm Oil

Some local natural sources of antioxidant such as orange peel extract (Citrus sinensis), pomegranate peel extract (Punica granatum) and ginger extract (Zingiber officinale L.) were evaluated during 5 days storage of refined palm oil at 63°C as compared to the synthetic antioxidant such as propyl gallate. The above extracts were obtained with ethanol and oil (palm oil). Those extracts were added to the oil at two different levels (100 ppm and 200 ppm). Antioxidant activity of natural extracts, synthetic antioxidant and the control treatment without antioxidant under thermal treatment (Schaal test) was assessed by measuring acid value (AV), peroxide value (PV), iodine value (IV) and refractive index (RI) during 6 days storage of refined palm oil at temperature mentioned above. Antioxidant activity also measured by studying the stability of oil by the use of rancimat method. All treatments exhibited antioxidant activity. Statistical analysis results were shown that the pomegranate peel extract treatment was significantly (P<0.05) superior than the orange peel extract and ginger extract treatments whereas, it was not significant difference about propyl gallate treatment.

Extraction of phenolic compounds from (Hops,grape seeds ) and study its antioxidant activity

The phenolic compounds were extracted from leaves and flowers of Hops and grape seeds from local production by soaking with different solvents (Methanol-ethanol-alcohol and water mixture) . The polyphenols content in the methanol extracts for 100 g dry matter was 6.31 g for the grape seeds, 2.08 g for Hops leaves and 0.6 g for Hops flowers. Methanol extracts were characterized by an antioxidant activity that appeared by their ability to Reduce ions ferriques Fe+3, at a concentration of 2500 ppm, the Reducing Power was 96.45% , 67.56% for the grape seeds and Hops leaves, respectively. The methanolic extracts of grape seeds and Hops leaves at 80 ppm showed activity in scavenge free radical DPPH. was 82.04% and 40.92% respectively. The methanolic extracts of grape seeds and Hops leaves at 250 ppm gave the ability to protect linoleic acid from the oxidation process of 78.98% and 48.41%, respectively. The antioxidant activity values of the extracts were compared with standard samples of ascorbic acid and BHT.