The extraction of phenolic compounds in peanut skin was carried out according to the method published by Nepote, Grosso, and Guzman (2005). Briefly, 20 mL of 70% ethanol was added to a flask containing 1 g of peanut skins. The flasks were shaken for 10 min using a Wrist Action Shaker (Model 75, Burrell Corp., PA, USA) at ambient temperature. The extract was filtered through a Whatman no. 1 filter paper and the residue was extracted again under the same conditions, for a total of three extractions.