Antioxidative and prooxidative effects in food lipids and synergism with a-tocopherol of açaí seed extracts and grape rachis extracts Priscilla Siqueira Melo a , Leandro de Oliveira Rodrigues Arrivetti b , Severino Matias de Alencar a , Leif H. Skibsted c,⇑ a Department of Agri-food Industry, Food and Nutrition, ‘Luiz de Queiroz’ College of Agriculture, University of São Paulo, Pádua Dias Avenue, P.O. Box 9, 13418-900 Piracicaba, SP, Brazil b São Carlos Institute of Chemistry, University of São Paulo, Trabalhador São Carlense Avenue 400, P.O. Box 780, 13560-970 São Carlos, SP, Brazil c Food Chemistry, Department of Food Science, University of Copenhagen, Rolighedsvej 30, 1958 Frederiksberg C, Denmark article info Article history: Received 11 March 2016 Received in revised form 27 June 2016 Accepted 29 June 2016 Available online 30 June 2016 Keywords: Euterpe oleracea Vitis vinifera Lipid peroxidation Antioxidant activity Antioxidant synergism Phenolic compounds abstract Extracts of açaí seed and of grape rachis alone or in combination with a-tocopherol were evaluated as antioxidants in (i) bulk soybean oil, (ii) soybean oil liposomes and (iii) soybean-oil/water emulsions. The extracts made with 57% aqueous ethanol showed an antioxidant activity not dependent on concentration for grape rachis extracts and a concentration-dependent prooxidative activity for açaí seed extracts in bulk soybean oil. Both the extracts, however, protected liposome suspensions and oil/water emulsions against lipid oxidation. Synergism was demonstrated when extracts were combined with a-tocopherol, effects explained by the solubility of extract components in the water-phase and of a-tocopherol in the lipid-phase. Phenolic profiling of the extracts by U-HPLC-ESI-LTQ-MS was used to identify active antioxidants. Açaí seed and grape rachis extracts served as good sources of procyanidins and flavan-3-ols, imparted high antioxidant activity especially when combined with a-tocopherol and are suggested for protection of food oil/water emulsions. Ó 2016 Elsevier Ltd. All rights reserved. 1. Introduction The requirements from consumers for natural and well-preserved healthy food are increasing. Associated with this, the agroindustrial sector develops new technologies to meet consumers’ expectation and searches at the same time for ways to reduce economic loss and to minimize environmental impact from an increasing amount of agroindustrial residues generated all over the world (Melo et al., 2015). Among the agroindustrial residues produced in Brazil, açaí seed and grape rachis are of special interest due to the increasing amount produced. The potential use of this rich resource is, however, still awaiting further studies and documentation. Açaí is a palm tree growing in the Amazon region and the consumption and commercialization of its pulp is expanding on many markets, mainly due to its antioxidative, anti-lipidaemic, anti-inflammatory (Martino, Dias, Noratto, Talcott, & Mertens- Talcott, 2016), anti-aging (Poulose et al., 2012) and anti- proliferative activities (Hogan, Chung, et al., 2010). Due to these functional properties açaí is often considered a ‘‘superfruit” (Yamaguchi, Pereira, Lamarão, Lima, & da Veiga-Junior, 2015). Açaí pulp is used for production of energy drinks, and the Brazilian production of açaí berries had a production in 2014 of 198 thousand tonne (IBGE, 2014). Associated with the açaí production and pulp processing, organic residues are generated, mainly seeds and peels, constituting up to 90% of the whole açaí berry weight (Wycoff et al., 2015), which represented 178 thousand tonne of seeds discarded into the environment in Brazil in 2014. In the winery industries, the generation of agroindustrial residues is also high. According to the Food and Agricultural Organization (2015), the total grape production in the world in 2013, was 77 million tonne. Solid residues represent around 30% of the volume of processed grapes (Makris, Boskou, & Andrikopoulos, 2007), and although there are many studies on grape pomace and seeds, studies on rachis are more scarce. Agroindustrial residues like from açaí and wine production are potential sources of phytochemicals with antioxidant activity (Melo et al., 2015; Wycoff et al., 2015). Many natural antioxidants have been studied for their beneficial effects on human health through contribution to the pre- vention of cardiovascular diseases (De Camargo, Regitano-D’Arce, Biasoto, & Shahidi, 2014; Vinson, Dabbagh, Serry, & Jang, 1995), inflammatory processes (Hogan, Canning, Sun, Sun, & Zhou, 2010), neurodegenerative diseases (Jeong et al., 2011), diabetes (Sun, Kadouh, Zhu, & Zhou, 2016), DNA damages (De Camargo http://dx.doi.org/10.1016/j.foodchem.2016.06.101 0308-8146/Ó 2016 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: ls@food.ku.dk (L.H. Skibsted). Food Chemistry 213 (2016) 440–449 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem