Optimization of phenolics and flavonoids extraction from the fruit of Empetrum nigrum var. japonicum from Jeju Island in South Korea

This study optimizes the extraction of phenolic and flavonoid compounds from Empetrum nigrum var. japonicum (crowberry) fruit using response surface methodology and evaluates the antioxidant activities of the extracts obtained. The optimized conditions predicted by Box-Behnken design were as followed: for total flavonoid content, extraction time is 43 min, extraction temperature is 52 °C, volume of solvent used for per gram of sample is 290 mL and ethanol concentration is 72%; the corresponding values for total phenolic content are 115 min, 58 °C, 670 mL, and 62%. The extracted phenolic and flavonoid contents under optimal conditions were 74.8 and 73.9 mg/g, respectively, which agreed with the prediction values of the model. In addition, crowberry extracts exhibited considerable scavenging ability to 2,2-dipheny-l,1-picrylhydrazyl and 2,2′-azinobis (3-ethylbenzothiazoline-6-sulphonic acid) radicals, and the maximum scavenging ability reached 92.6% and 100.0%, respectively. This study is of great significance for the promoting the development of crowberry industry and the exploiting of natural antioxidant.