Optimization of ultrasound-assisted extraction of ascorbic acid from fennel (Foeniculum vulgare) seeds and evaluation its extracts in free radical scavenging

Abstract

The main objective of this study was to compare ultrasound assisted extraction with soxhlet extraction method as control in the extraction ascorbic acid of fennel seeds. Treatment conditions were performed using soxhlet method (240 min at 85 °C) and ultrasound treatment (20 kHz, 39, 64 and 96 W/cm², 40 and 60 °C), for 15, 30 and 45 min. No significant differences were observed for total soluble solids among the samples studied. A similar trend was observed for both the amount of ascorbic acid extract and its ability to DPPH free radical scavenging. The greatest amount of ascorbic acid obtained in 15 minutes sonication (96 W/cm² at 60 °C), with equivalent of 1.73 mg/ml fennel seeds extraction. There was a significant difference between soxhlet and ultrasound method, which caused an increase of 69.94 mg/ml ascorbic acid in the extraction compared to the soxhlet. The highest percentage of hydrogen peroxide scavenging was observed in 15 min sonication (96 W/cm² at 60 °C) equivalent to 74.13% without any significant difference with soxhlet method (6.93% increase in free radical). The highest percentage of DPPH free radical scavenging was observed in 15 min sonication (96 W/cm² at 60 °C) equivalent to 98.88% without any significant difference with soxhlet method (0.18% increase in free radical). The results of the present study demonstrate that ultrasound assisted extraction is an alternative affordable for yield extraction compared to soxhlet method.