Anti-oxidative effects of normal and encapsulated extract of Fleawort (Plantago ovate) on the oxidative stability of a food model system (sunflower oil)

Free radicals may cause lots of diseases in humans and oxidative degradation of lipids is a major factor limiting the shelf life of foods. The free radical reaction of lipid peroxidation is generally responsible for the deterioration of lipid-containing foods. Use of antioxidants during the manufacturing process can minimize the extent of lipid peroxidation. Phenolic antioxidant compounds can prevent the destructive effect of free radicals and their resulting mutation. Sunflower oil is widely used in nutrition as a source of essential linoleic (9-cis, 12-cis-octadecadienoic) acid. The present study explored the chemical constitution and antioxidant activity of Fleawort (Plantago ovate) extract and the effect of these natural antioxidants on sunflower oil. It is well known that edible oils used as cooking medium at high temperatures in the presence of oxygen are subject to therm-oxidation, polymerization, and hydrolysis, and the resulting decomposition products not only produce undesirable off-flavors, but can also decrease the nutritional quality of the fried product.
Material and The present study was carried out in refined sunflower oil, free of additives, supplemented by pure concentration levels of normal and encapsulated extract of Fleawort (i.e., 200, 500, 700 and 1000 ppm) and one level of BHT (200) ppm .The doses of Fleawort extract were chosen in agreement with previous studies that have proved that the inhibitory effect on lipid oxidation increased with the antioxidant concentration In this research the phenolic content of the ethanol extract of Fleawort was determined by Folin–Ciocalteu method. The antioxidant activity of this extract was evaluated using DPPH• and ABTS methods. Furthermore, the oven tests including peroxide and thiobarbituric acid values were done at 65º C in sunflower oil.
The results showed that different concentrations of this extract were effective in retarding the oil oxidation at 65ºC. Among the treatments, the 1000 ppm Concentration of encapsulated extract has higher antioxidant activity than other treatments during storage time. Based on the evaluation results of phenolic compounds in Plantago ovata extract, the amount of phenolic compounds of this extract will be increased according to the concentration of the extract. Although this index was the highest in treatment of EN 1000, there was no significant difference between the ordinary and encapsulated treatments (p>0/05). According to DPPH Evaluation Test for determining the antioxidant capacity of the samples, the highest amount of DPPH was seen in treatment of EN 1000 (p0/05). Also, based on the Restoration Power Test, treatment of EN 1000 had the most meaningful restoration power and in all concentrations of the extract and treatment showed the most meaningful restoration power (p