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Total Oxidant Scavenging Capacity of Euterpe oleracea Mart. (Açaí) Seeds and Identification of Their Polyphenolic Compounds
Roberta B. Rodrigues, Ramona Lichtenthäler, Benno F. Zimmermann, Menelaos Papagiannopoulos, Heinz Fabricius, and Friedhelm Marx*
Institute of Nutrition and Food Sciences, Department of Food Chemistry I, University of Bonn, Endenicher Allee 11-13, D-53115 Bonn, Germany
José G. S. Maia and Ossalin Almeida
Department of Chemistry and Food Engineering, Federal University of Par, Rua Augusto Corrêa 1, 66075-900 Belém, PA, Brazil
Received for review November 3, 2005. Accepted March 21, 2006. This work was supported by the Unilever Deutschland GmbH (Hamburg, Germany).
Abstract:
The antioxidant capacity of methanol and ethanol seed extracts from Euterpe oleracea Mart. (açaí) against the reactive oxygen species (ROS) peroxyl radicals, peroxynitrite, and hydroxyl radicals was studied with the total oxidant scavenging capacity (TOSC) assay in a modified and automated version. Cold methanol digestion was the most efficient extraction method with respect to the antioxidant capacity. The extracts exhibit good antioxidant capacity against peroxyl radicals, similar to the capacity of the pulp. The antioxidant capacity against peroxynitrite and hydroxyl radicals is even higher. The main antioxidants identified by HPLC-MS and HPLC-CEAD are five different procyanidins (di- through pentamers); furthermore, protocatechuic acid and epicatechin were identified as minor compounds. Determination of TOSC values of HPLC seed extract fractions indicates that the procyanidins contribute substantially to the overall antioxidant capacity. In addition, however, other compounds that have not yet been identified are responsible for a large part of the observed antioxidant capacity.
Keywords: Euterpe oleracea; açaí; seed extract; TOSC assay; antioxidant; peroxyl radicals; peroxynitrite; hydroxyl radicals; procyanidins