Extraction and purification of walnut (Juglans regia L.) phenolic fractions with antioxidant activity

LABUCKAS, DIANA; MARTÍNEZ, MARCELA; MATTEA, MIGUEL; LAMARQUE, ALICIA; MAESTRI, DAMIÁN

Foz do Iguaçu

Conferencia; International Conference of Agricultural Engineering - XXXVII Congresso Brasileiro de Engenharia Agrícola; 2008

Walnut (Juglans regia L.) seeds have an important amount of phenolic compounds, which are mostly present in the hull. When seeds are whole-ground and the oil is extracted, most phenolics remain in the meal cake wherefrom they can be extracted using aqueous ethanol solutions. In this study the antioxidant activity of phenolic extracts from walnut pre-pressed meal cake was investigated. Phenolic compounds were extracted with water:ethanol 30:70 v/v. The crude extract was defatted and then passed through a porous polymer gel (Diaion HP 20 column). The adsorbed materials were eluted successively with water, water:ethanol (90:10 and 80:20, v/v) and ethanol. The water:ethanol 80:20 v/v extract showed the highest total phenolic content (12.21 mg gallic acid equivalent/g dry deffated extract) and provided an EC50 value (3.74 µg/ml) lower than BHT and ascorbic acid (8.49 and 4.13 µg/ml, respectively). An interesting application of walnut phenolic extracts is related to their antioxidant properties as it was demonstrated by their radical scavenging effect.