EVALUATION OF ANTIOXIDANT ACTIVITIES FROM VARIOUS EXTRACTS OF SWEET ORANGE PEELS USING DPPH, FRAP ASSAYS AND CORRELATION WITH PHENOLIC, FLAVONOID, CAROTENOID CONTENT

Objectives. The objectives of this research were to study antioxidant capacity from various extracts of sweet orange peels using two methods of antioxidant testing which were DPPH (2.2-diphenyl-1-picrylhydrazyl) and FRAP (Ferric Reducing Antioxidant Power) and correlation of total phenolic, flavonoid and carotenoid content in various extracts of sweet orange peels with DPPH and FRAP antioxidant capacities. Methods. Extraction was performed by reflux using various solvents. The extracts were vaporated using rotavapor. Then antioxidant capacities were tested using DPPH and FRAP assays. Determination of total phenolic, flavonoid and carotenoid content were performed by spectrophotometry UV-Vis and its correlation with FRAP and DPPH antioxidant capacities were analyzed by Pearson method. Results. KT3 (ethanol peel extract of Kintamani orange) had the highest DPPH scavenging capacity with IC50 2.25 ppm and KT3 had the highest FRAP capacity also with EC50 131.7 ppm. KT3 contained the highest total phenolic (10.08 g GAE/100 g), KT2 (ethyl acetate peel extract of Kintamani orange) had highest flavonoid content (9.94 g QE/100 g) and BW1 had the highest carotenoid 2.33 g BET/100 g. Conclusions. There were positively high correlation between total phenolic content in all of peels samples with their antioxidant activity using DPPH and FRAP assays. DPPH scavenging capacities in all of orange peels samples had positively high correlation with their FRAP capacities. Keywords: Antioxidants, FRAP, DPPH, sweet orange peels, flavonoid, phenolic, carotenoi