Electrochemical behaviour and antioxidant capacity of anthocyanins from Chilean red wine, grape and raspberry

Abstract

abstract The anthocyanin fractions were extracted from Cabernet Sauvignon red wine, skins of Vitis vinifera grapesand raspberry fruits (Rubus idaeus). In red wine extract, 16 anthocyanins were identified, malvidin-3-O-glucoside being the main anthocyanin, which comprised 53.6% of the total anthocyanin in grape extract.Raspberry extract contained mainly delphinidin-3-O-glucoside and cyanidin-3-O-glucoside. The antiox-idant capacity of the extracts was assayed by electrochemical methods. Best resolution of the oxidationpeaks for the extracts and diluted wine was obtained by pulse differential voltammetry. The wine diluted20 presented values of P1 (443 mV) and P2 (676 mV) similar to those corresponding to wine extract,and to the anthocyanin malvidin-3-O-glucoside. The antioxidant capacity of anthocyanins in extractsof wine, grape skin and raspberry fruit was also determined by the Trolox equivalent antioxidant capacity(TEAC) method. 2009 Elsevier Ltd. All rights reserved. 1. IntroductionRed wine is a complex system which contains a large variety ofphenolic compounds, such as flavonols, flavan-3-ols, anthocyaninsand phenolic acids. Anthocyanins are extracted from red grapesand are largely responsible for the colour exhibited by red wine;they play an important role in the antioxidant activity of red wine(Zoecklein, Fugelsang, Gump, & Nury, 2001). In red wine, anthocya-ninsinteractwithphenolicscompounds,pyruvicacidandacetalde-hyde to give new pigments (Francia-Aricha, Guerra, Rivas-Gonzalo,SFulcrand,Bernabdeljalil,Rigaud,Cheynier,M Mateus, Silva, Vercauteren, & De Feitas, 2001).The antioxidative capacity of anthocyanin was studied by differentchemical methods. The Folin–Ciocalteu method, the oxygen radicalabsorbancecapacity(ORAC)assayandtheTroloxequivalentantiox-idantcapacity(TEAC)assayarethemostconsideredmethods(Prior,Wu, & Schaich, 2005). Kilmartin and Hsu (2001) developed anelectrochemical method for the characterization of the antioxidantproperties of wine and wine phenolics. Recently, Janeiro andOliveira Brett (2007) studied the redox behaviour of anthocyaninsby voltammetric techniques, they found that all the phenolichydroxylgroupscanbeelectrochemicallyoxidized.DaSilva,RamosStradiotto,andOliveira(2008)developedamethodforthedetermi-nation of caffeic acid in red wine by differential pulse voltammetry.Zienlin´ska, Nagels, and Piskula (2008) determined the antioxidantcapacity of quercetin and its glycosides of onion by cyclic voltam-metry. Ghiselli, Nardini, Baldi, and Scaccini (1998) reported thatamong the red wine components, anthocyanins were the mosteffectiveinscavengingreactiveoxygenspecies(ROS)andinhibitinglipoprotein oxidation. Anthocyanins comprise around 70% of thetotalphenolsofItalianredwine.Inthisworkweevaluatedtheelec-trochemical behaviour of Chilean Cabernet Sauvignon red wine,Vitis vinifera grape and raspberry anthocyanin extracts in a modelwine solution at pH 3.6, and in acetate buffer.2. Materials and methods2.1. MaterialsCabernet Sauvignon red wine vintage 2005 and V. viniferagrapes were supplied by a local producer. Mature raspberry fruits(Rubus idaeus) were purchased in the local market. All the solventswere reagent grade and/or HPLC grade (Merck, Darmstadt,Germany), all the chemicals were reagent grade (Sigma, St. Louis,MO, USA).2.2. HPLC analysisFor the high performance liquid chromatography (HPLC) analy-sis a Waters 600 HPLC chromatograph (Waters, Mildford, MA, USA)equipped with a Waters 2990 diode array detector, and a