Strawberry consumption improves plasma antioxidant status and erythrocyte resistance to oxidative haemolysis in humans Sara Tulipani a,1 , Josè M. Alvarez-Suarez a , Franco Busco b , Stefano Bompadre c , Josè L. Quiles d , Bruno Mezzetti e , Maurizio Battino a,⇑ a Department of Biochemistry, Biology & Genetics, Faculty of Medicine, Marche Polytechnic University, Ancona, Italy b Analysis Laboratory of INRCA Hospital, Ancona, Italy c Department of Biomedical Sciences, Faculty of Medicine, Marche Polytechnic University, Ancona, Italy d Institute of Nutrition and Food Technology Mataix Verdú, Department of Physiology, University of Granada, Granada, Spain e Department of Environmental and Crop Science (SAPROV), Faculty of Agriculture, Marche Polytechnic University, Ancona, Italy article info Article history: Received 16 September 2010 Received in revised form 30 December 2010 Accepted 4 March 2011 Keywords: Strawberry Vitamin C Plasma total antioxidant capacity Antihaemolytic effects abstract Significant increases in the plasma total antioxidant capacity (TAC) have already been reported after acute intake of strawberries. In addition, antihaemolitic effects of strawberry extracts have been recently demonstrated in vitro, revealing that part of the antioxidant properties of strawberry bioactive com- pounds could lie in their localisation within cell membranes. However, there is a lack of research evi- dence from in vivo protracted strawberry consumption studies. We carried out a 16-day pilot study where 12 healthy subjects ingested 500 g of antioxidants-rich strawberries daily, and we evaluated the potential effects of fruit consumption on biomarkers of plasma and cellular antioxidant status. A signif- icant increase in fasting plasma TAC and in serum vitamin C concentrations were progressively observed during the period of strawberry supplementation. An enhanced resistance to haemolysis was also observed in both AAPH-treated and untreated erythrocytes, collected during and after the period of strawberry consumption. The results obtained in this work suggest that regular consumption of antiox- idant-rich strawberries may exert an improvement on the plasma antioxidant status and an increase on the antihaemolitic defenses of human erythrocytes. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Dietary antioxidants from fruit seem to fill an important bene- ficial role in improving the antioxidant defenses of the human body against the development of chronic diseases (Hung et al., 2004; Sun, Chu, Wu, & Liu, 2002), and the consumption of fruit at each meal has been recommended in order to prevent periods of post- prandial oxidative stress (Prior et al., 2007). The strawberry (Fragaria  ananassa, Duch.) is one of the most commonly consumed berries. Its high nutritional value has long been correlated to the relevant content of antioxidant micronutri- ents, such as vitamin C and folate, and more recently to the high variety and content of antioxidant polyphenolic constituents, such as flavonoids, hydrolysable and condensed tannins, and phenolic acids (da Silva Pinto, de Carvalho, Lajolo, Genovese, & Shetty, 2010; Seeram, Lee, Scheuller, & Heber, 2006). Significant increases in plasma total antioxidant capacity (TAC) have already been reported after acute intake of strawberries (Cao, Russell, Lischner, & Prior, 1998; Prior et al., 2007). In parallel, previous authors observed acute increases of serum urate after con- sumption of several fruits, explained through a fructose-mediated overproduction of this endogenous compound after fruit consump- tion (Lotito & Frei, 2004; Natella, Nardini, Giannetti, Dattilo, & Scaccini, 2002). Due to the well-known high reducing and free rad- ical scavenging activities of urate, which alone may contribute to up to 60% of the plasma TAC, the authors ascribed the observed increase in the plasma antioxidant status to the raise of this endog- enous metabolite. In contrast, we recently demonstrated that the improvement in the plasma antioxidant status after acute consumption of strawberries was mainly correlated to a significant 0308-8146/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2011.03.025 Abbreviations: AAPH, 2,2 0 -azobis(2-amidinopropane) dihydrochloride; ABTS, 2,2 0 -azino-bis(3-ethylbenzothiazoline-6-sulphonic acid); ACY, total anthocyanin content; BMI, body mass index; Chol, cholesterol; CTAB, hexadecyltrimethylam- monium bromide; FRAP, ferric reducing antioxidant power assay; FW, fresh weight; LDL, low density lipoprotein; PBS, phosphate buffered saline; RBC s , red blood cells; RDA, recommended dietary allowance; SD, standard deviation; SEM, standard error; TAC, total antioxidant capacity; TE, trolox equivalents; TEAC, trolox equiv- alent antioxidant capacity assay; TFC, total flavonoid content; TPC, total phenolic content. ⇑ Corresponding author. Address: Institute of Biochemistry, Faculty of Medicine, Marche Polytechnic University, Via Ranieri, 65, 60100 Ancona, Italy. Tel.: +39 071 2204646; fax: +39 071 2204398. E-mail address: m.a.battino@univpm.it (M. Battino). 1 Present address: Department of Nutrition and Food Science-CeRTA, Faculty of Pharmacy, University of Barcelona, Barcelona, Spain. Food Chemistry 128 (2011) 180–186 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem