No abstract

Mandarin and lime peels are rich sources of phenolic compounds including phenolic acids and flavonoids. The ultrasound-assisted extraction (UAE) proved to be an effective method in the extraction of phenolic compounds from plants due to its ability to save extraction time and increase extraction yields. In this research, factorial randomized complete experimental design has been used to investigate the effect of various factors on UAE using low power (50.93 W). Influence of citrus peel types and solvent types and concentrations on the total phenolic compounds, total flavonoids, and flavanone glycosides (hesperidin and naringin) were studied. Antioxidant activity of the extracts was measured by ferric reducing antioxidant potential (FRAP), azinobis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), and 1,1-diphenyl-2-picrylhydrazyl (DPPH) assays. The optimum extraction conditions occurred when mandarin peel and 80 % acetone were used. In those conditions, the extract contained 3,083.61 mg gallic acid equivalent (eq) 100 g −1 dry weight (DW) of total phenolic compounds, 2,539.82 mg quercetin eq 100 g −1 DW of total flavonoid, 1,374.20 mg 100 g −1 DW of hesperidin, and the measured antioxidant activity was 0.61 mg mL −1 of DPPH IC 50 , 1.12 mg mL −1 of ABTS IC 50 , and 2,521.47 mg trolox eq 100 g −1 for FRAP. A strong correlation between total phenolic content and antioxidant activity was also observed.