Effect of ultrasound waves on the amount of ascorbic acid extraction from fennel seeds and potential of its extraction for improvement of antioxidant properties

Fennel as a medicinal plant has substances and valuable secondary metabolites such as ascorbic acid, which is able to scavenging free radicals produced by oxidation. In common extraction methods such as soxhlet long time and high energy consumption is required and there is a possibility of damage for heat-sensitive substances including ascorbic acid. Therefore, in this study the used modern method of ultrasound compared with conventional method by using soxhlet as a control treatment on the ascorbic acid extracted from the fennel seeds and its potential of scavenging of hydrogen peroxide. The samples were extracted at 85 °C for 240 minutes in soxhlet method while in ultrasound method the samples were examined at two temperatures (40 and 60°C), three sonication duration (15, 30 and 45 min) and three sonication powers (100, 200 and 300W). The results of this study showed that the optimum extraction condition in ultrasound method was at 60°C, 300W and 15min for both ascorbic acid content and hydrogen peroxide scavenging percentage by the extracts. The ascorbic acid content of 1.73 mg/mL and the percentage of containment of hydrogen peroxide of 74.13% were resulted under these conditions for fennel seed extracts that was significantly different compare with soxhlet method and caused an increase in extraction of ascorbic acid and hydrogen peroxide scavenging method. So superiority of ultrasound method was proved because of reduction in time and temperature.