Fe(III) improves antioxidant and cytoprotecting activities of mangiferin Gilberto L. Pardo-Andreu a,b, ⁎ , Carlos Sánchez-Baldoquín a , Rizette Ávila-González a , René Delgado a , Zeki Naal b , Carlos Curti b a Departamento de Investigaciones Biomédicas, Centro de Química Farmacéutica, Calle 200, Esq. 21,Playa, Ciudad de La Habana, Cuba b Departamento de Física e Química, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, 14040-903 Ribeirão Preto, SP, Brazil Received 28 April 2006; received in revised form 15 July 2006; accepted 19 July 2006 Available online 28 July 2006 Abstract Iron-induced oxidative stress has been implicated in several pathological processes. In the present work we provide evidence for the formation of a mangiferin:Fe(III) complex (2:1), shown by means of either iron-induced changes in the UV/visible spectrum of mangiferin or by reduction of the anodic current peak in the voltammogram of that compound; we demonstrate, in addition, that the ferric complex is more effective than mangiferin itself in scavenging superoxide radicals generated by pyrogallol autoxidation, as well as in protecting hepatocytes from reactive oxygen species mediated hypoxia/reoxygenation injury. Moreover, we found that the mangiferin:Fe(III) complex reacts more readily with horseradish peroxidase/H 2 O 2 than does mangiferin by itself. We postulate that mangiferin could afford protection against iron/reactive oxygen species-mediated pathological processes by means of both iron chelating and iron-stimulated superoxide radical scavenging activity. © 2006 Elsevier B.V. All rights reserved. Keywords: Mangiferin; Polyphenols; Iron; Superoxide scavenging; Cytoprotection 1. Introduction Mangiferin (1,3,6,7-tetrahydroxyxanthone-C2-β-D-glucoside) (Fig. 1) is a xanthone derivative (Aritomi and Kawasaki, 1969) widely distributed in higher plants like those of the Anacardiaceae and Gentianaceae families. In addition to its well-documented antioxidant property (Sato et al., 1992; Sanchez et al., 2000; Ghosal et al., 1996), mangiferin presents several pharmacological activities including anti-diabetic (Ichiki et al., 1998), anti-HIV (Guha et al., 1996), anti-cancer (Yoshimi et al., 2001), immunomodulatory (Leiro et al., 2004), and anti-inflammatory properties (Garrido et al., 2004). The catechol moiety, which is capable of forming stable complexes with iron, is likely to contribute to the antioxidant activity of mangiferin (Sato et al., 1992; Sanchez et al., 2000; Ghosal et al., 1996). We have previously demonstrated that mangiferin protects isolated mito- chondria from membrane lipid peroxidation induced by Fe(II)- citrate (Andreu et al., 2005a,b), as well as inhibits 2-deoxyribose damage induced by Fe(III)-EDTA-Ascorbate (Pardo-Andreu et al., 2006). The stoichiometry of the mangiferin–iron complex for these effects exceeded mangiferin's ability to coordinate iron, so that this property cannot solely account for them. Indeed, ferric ions have been demonstrated to improve superoxide radical scavenging activity and cytoprotection by some catechols (Zhao et al., 1998; Kostyuk et al., 2004). In the present work we have studied the mangiferin:Fe(III) complex by UV–visible spectrophotometry and cyclic voltammetry, and have observed that it is more effective than mangiferin itself both in scavenging superoxide radicals generated by pyrogallol autoxidation and in protecting hepatocytes from reactive oxygen species-mediated hypoxia/reoxygenation injury. 2. Materials and methods 2.1. Reagents and solutions Mangiferin, dimethyl sulfoxide (DMSO), ferric chloride, tris (hydroxymethyl)aminomethane (TRIS), N-(2-hydroxyethyl) piperazine-N′-(2-ethanesulfonic acid) (HEPES), ethylenediami- netetraacetic acid (EDTA), and horseradish peroxidase were obtained from Sigma–Aldrich Corp. (St. Louis, MO, USA). European Journal of Pharmacology 547 (2006) 31 – 36 www.elsevier.com/locate/ejphar ⁎ Corresponding author. Departamento de Investigaciones Biomédicas, Centro de Química Farmacéutica, Calle 200, Esq. 21,Playa, Ciudad de La Habana, Cuba. Tel.: +53 7 2085106; fax: +53 7 2736471. E-mail address: g031071@yahoo.com (G.L. Pardo-Andreu). 0014-2999/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.ejphar.2006.07.040