Comparison of chemical composition and antioxidant activity of essential oils of orange peel in two ways supercritical fluid extraction and hydro distillation

In this research, the effect of two methods of namely extraction (supercritical fluid) and traditional extraction (distillation with water) on the yield, chemical composition and antioxidant activity of essential oil of orange peel were studied. The whole process in the traditional method took longer than the new method and generally the yields of obtained essential oil by supercritical fluids (8.3%) was more than water distillation method (2.5%) respectively and chemical composition of essential oils was identified and the percentage of compounds was measured using gas chromatography- mass spectrometry. According to the results of chromatography, D-limonene which is the main composition of essential oil of orange peel had the highest frequency in both methods compared to the other components of the essential oil. But the amount of D-limonene in extractions by distillation method (86.58%) was more than supercritical fluids method (69.71%) respectively. However, according to the chromatogram, the amount of phenol in the essential oil of supercritical fluids (1.49%) was more than distillation method (0.03%), which is in accordance with the phenol comparison in the Folin-Ciocalteu test. Then the antioxidant activity of essential oils was evaluated using DPPH free radical scavenging methods and reducing ability. Finally, essential oil of supercritical fluids, showed a higher antioxidant activity than water distillation. In other words, the lowest IC50 (the highest antioxidant activity) is equal to 35.98 mg/ml in DPPH method of supercritical fluid extraction method.