Satsuma mandarin, which is also known as Citrus unshiu, contains high amount of polyphenols and antioxidants. This study focused on the biowaste valorization of bioactive compounds used for food supplementary. For this purpose, ultrasonic extraction method was utilized. The antioxidant capacity and polyphenolic content of the Citrus unshiu extracts were determined. The number of experiments was reduced owing to the response surface methodology (RSM) and particle swarm optimization (PSO). Therefore, the extraction process has become more economical. In this study, according to the RSM, optimal conditions were determined as 90 min, 56% amplitude, and 50 degrees C. PSO suggested the optimal conditions as follows: 27 min, 50 amplitude, and 52 degrees C. For the performance metrics, RSM gave higher satisfactory results than PSO. For RSM, 8.953 GA/g-peel and 5.253 catechin/g-peel were obtained as total phenolics content (TPC) and total flavonoids content (TFC). For PSO, 6.977 GA/g-peel and 6.454 catechin/g-peel were obtained as phenolics and flavonoids. The highest R-values for TPC (0.9947) and TFC (0.9825) were obtained by RSM. The results proved that Citrus unshiu peel contains highly rich phenolic and high value-added bioactive compounds.