Extraction of phenolics from citrus peels: I. Solvent extraction method

The total phenolic contents of five citrus peels (Yen Ben lemon, Meyer lemon, grapefruit, mandarin and orange) extracted either by ethanol or by simple aqueous extraction were evaluated using the Folin-Ciocalteu assay and compared. The main parameters that affected the yield of phenolics included the condition of the peels, temperature of the extraction, solvent concentration and species of citrus. Generally, grapefruit peel had the highest total phenolic contents, followed by mandarin, Yen Ben lemon, orange and Meyer lemon peel. High extraction (about 74%) was obtained using ethanol as solvent and the percentage extraction could further be increased using a higher temperature of 80 °C. In addition, the total antioxidant activity of the phenolic contents extracted from different citrus peels were investigated using the FRAP assay. The phenolics in grapefruit peels had the highest total antioxidant activity, followed by Yen Ben lemon, mandarin, orange and Meyer lemon.