Phytochemical content and antioxidant capacity of water-soluble isolates from peanuts (Arachis hypogaea L.)

Numerous polyphenolics have been identified in peanuts, but information relating to their storage stability and contributions to total antioxidant capacity are lacking. This study investigated contributors to the antioxidant capacity of six peanut cultivars by means of fractionation from reversed phase C18 cartridges. Five water-soluble peanut isolates were prepared and subsequently stored at 35 °C and evaluated for individual and total polyphenolics, antioxidant capacity, total reducing equivalents, and total amino acids after 0, 2, 4 and 8 weeks. The relative contribution of each isolate to total antioxidant capacity for each cultivar was additive, with the C18 non-retained fraction containing 100% of the p-coumaric acid and 82% of the total amino acids. During storage relatively small changes were observed for antioxidant activity and total reducing equivalents among cultivars and isolates, indicating the lack of oxidative or condensation reactions among the isolated constituents. Results demonstrated the overall stability and diversity of antioxidant polyphenolics found in peanuts, information that advances the marketability of the crop.