Optimization of ultrasound-assisted extraction in limau peels (Citrus amblycarpa), antioxidant activity and its potential as an inhibitor for xanthine oxidase

Antioxidant content in limau peel (Citrus amblycarpa) is well recognized to be high. Free radicals can be neutralized by antioxidants, which can then be employed as natural active components in pharmaceuticals. One of them is an alternative xanthine oxidase (XO) inhibitor in lowering uric acid levels. Limau peel was extracted using the Ultrasound-Assisted Extraction method with ultrasonic waves showed optimum condition at amplitude of 45 in 50 minute and amplitude of 60 in 50 minute. The yield obtained was 9.07%. These results are obtained quickly without the use of solvents and excess energy. The results of phytochemical screening showed the presence of several secondary metabolites in limau peel extract, including Tannins, Phenolics, Glycoside Steroids, Flavonoids, and a small amount of Saponins. This study tested antioxidant activity using 3 different methods: the DPPH, CUPRAC, and FRAP methods. The antioxidant test results are shown in IC50 values with optimal gains of 33.40±0.01mg/L for DPPH, respectively; 21.38±0.04mg/L for CUPRAC; and 15.31±0.02mg/L for FRAP. Meanwhile, in testing the potential as a xanthine oxidase inhibitor, it was found that limau peel extract could reduce uric acid levels in vitro by 71.63±0.94%.