Recovery of Phenolic Compounds from Citrus Peel Through Solid Phase Extraction and QuEChERS as Clean-up Methods

Introduction: Citrus peel, one of the main byproducts of the food industry, is an important source of phenolic compounds with preventive and protective effects. The analysis of these compounds has been widely described, however, information on the purification methods of the extracts is limited. Objective: The objective of the present study is to determine the purification method that favors the obtaining of phenolic compounds from citrus peel extracts. Methods: Oranges (C. sinensis) and mandarins (C. reticulata) were purchased from a local supermarket (Valencia, Spain). The peels were separated manually and cut into pieces of 25 mm². An ultrasound-assisted extraction was performed (30 min, 400 W, < 40 °C). Purification by Solid Phase Extraction (SPE) was carried out using cartridges with 200 mg of C₁₈. The QuEChERS procedure was performed using 2 ml DisQUE™ Tubes. The profile of phenolic compounds was analyzed by HPLC-UV. Results: The major compounds in the samples were narirutin and hesperidin. Differences were determined according to both purification methods (p < 0.05). Hesperidin was higher in orange peel samples (2229 µg/g FW), while the highest amount of narirutin was obtained in tangerine peel (440 µg/g FW). Conclusion: The sample purification methods are selective. The QuEChERS method showed a greater recovery of phenolic acids and quercetin. The content of phenolic acids was higher in mandarin peel samples.