evaluation of antioxidant activity of essential oil extracted from ferula gummosa boiss in deep oil frying

introduction: 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 fatty foods. in general, use of synthetic antioxidants during the manufacturing process are applied to prevent fat oxidative and rancidity while their carcinogenic effects have been approved. since the use of synthetic preservatives in food have been declined, researches on alternative natural products such as aromatic plants extract and essential oil have been extended.aromatic plants are used traditionally in various regions of iran for their preservation and medicinal properties, in addition to enhancing the aroma and flavor of foods. aromatic plants components that have antiradical activities were used as natural antioxidant in food and biological products. the aim of this research was extraction and identification of the chemical compounds of ferula gummosa bioss essential oil and investigation of its antioxidant capacity in frying oil. materials and methods: aerial parts of f. gummosa were collected during fall 2013 from khouzestan province of iran. the collected aerial parts were then dried in the shade. the essential oil of aerial parts was extracted by hydro-distillation technique using clevenger apparatus. analyses of isolation, identification, and quantification of the component of the essential oil of f. gummosawere performed with a gc coupled with a mass spectrometer detector gc/ms. analyses were carried out using helium as the carrier gas on db-5 column (30 m×0.25 mm i.d., 0.25 μmfilmthickness). injector and detector were hold at 240 and 300°c, respectively, and 0.5 μl of the diluted essential oil was injected. identification of most of the compounds was made according to gc-ms retention times (authentic chemicals), kovats indices (ki) in reference to n-alkanes (c8–c24), and mass spectra (authentic chemicals and nist05 spectral library collection). identification was considered tentative when it was based on mass spectral data only. volatile compounds were quantified using percentage peak area calculations by means of a gc-fid with the same column and nitrogen as the carrier gas. the total phenol content in the f. gummosaessential oil was determined by a spectrometric method, according to the folin–ciocalteu phenol method by mixing of 0.2 ml of the essential oil with folin-ciocalteau reagent diluted and na2co3. the absorbance was measured at 765 nm after incubation in the dark at ambient temperature. the results of the total phenolic contents were expressed as gallic acid equivalents.the dpph (2,2-diphenyl-1-picrylhydrazyl) and abts [(2,2´-azino-bis 3-ethylbenzthiazoline-6-sulphonic acid)]tests were used for estimating antioxidant effects because the dpph and abts radicals are the two most widely used and stable chromogen compounds to measure the antioxidant activity of biological material. in addition, the model of the dpph radical-scavenging and abts radical cationdecolorization assay can be used to evaluate the antioxidant activities in a relatively short time compared with other methods. for this purpose 0.05 ml of the essential oil at different concentrations (0.05, 0.1, 0.2, 0.5, 1, 2, 5, 10 mg/ml) were mixed with 5 ml of 0.2 mmmethanolic dpph solution and kept in the dark for 30 min at room temperature, then absorption-decrease was measured at 517 nm. the radical scavenging activity assessed by the abts method was expressed as the teac (trolox equivalent antioxidant capacity) value based on absorbance at 734 nm. in this test, ascorbic acid was used as positive control. the antioxidant activity of essential oil was evaluated against tertiary butylhydroquinone (tbhq) as an synthetic antioxidant in frying oil by peroxide value and thiobarbituric acid (tba) index under rush condition in 90° c during one week. results & discussion: gc-ms analysis of the volatile constituents of the f. gummosa essential oil allowed the identification of twenty-nine compounds representing 96.80% of the total volatile oil. the main components were β- pinene (37.9%), α- pinene (9.05%), terpinene-4-ol (7.78%) and ρ- cymene (6.58%). the mean amount of total phenolic of obtained essential oil was 59.7 mg gallic acid/g dry plant material.in the present study, the essential oil showed good free radical scavenging capacity at all concentrations studied, however the scavenging activity increased with increasing concentration of the essential oil. antioxidant activity of essential oil from f. gummosa at 1 mg/ml was similar to tbhq at 0.1 mg/ml (p ≤ 0.05%). the scavenging capacity test showed that the ec50 value of the essential oil was found to be 0.094 mg/ml. abts test showed that the f. gummosaessential oil was able to reduce the stable radical and 1mg/ml of essential oil had the highest antiradical activity (0.113 mg/ml ascorbic acid equivalent). oven test revealed that 500 and 1000 ppm of essential oil had the higher activity than tbhq in 200 ppm in frying oil. conclusion: the results indicated that f. gummosa had high total phenolic content. also, according to these results, there was a relationship between totalphenolic content and antioxidant activity.the findings of this study showed that f. gummosa essential oil can exhibit strong antioxidant activity, probably due to its particular chemical composition, mainly the high amounts of monoterpenes. therefore, this essential oil could be used for the preservation of edible oil against oxidation and for increasing its shelf life as a natural preservative ingredient.