Low Molecular Weight Phenolics of Grape Juice and Winemaking Byproducts: Antioxidant Activities and Inhibition of Oxidation of Human Low-Density Lipoprotein Cholesterol and DNA Strand Breakage Adriano Costa de Camargo, †,§ Marisa Aparecida Bismara Regitano-d’Arce, § Aline Camara ̃ o Telles Biasoto, # and Fereidoon Shahidi* ,† † Department of Biochemistry, Memorial University of Newfoundland, St. John’s, Newfoundland, Canada A1B 3X9 § Department of Agri-Food Industry, Food and Nutrition, “Luiz de Queiroz” College of Agriculture, University of Sã o Paulo, Av. Pa ́ dua Dias 11, P.O. Box 9, CEP 13418-900 Piracicaba, São Paulo, Brazil # Embrapa Semia ́ rido, Rodovia BR 428, km 152, P.O. Box 23, CEP 56302-970 Petrolina, Pernambuco, Brazil ABSTRACT: Bioactive compounds belonging to phenolic acids, flavonoids, and proanthocyanidins of grape juice and winemaking byproducts were identified and quantified by HPLC-DAD-ESI-MS n . The concentration of phenolic compounds in different grape cultivars was in the order Tempranillo > Cora > Syrah > Isabel. The insoluble-bound fraction was most prominent, contributing 63 and 79% to the total for Isabel and Tempranillo, respectively. Juice-processing byproducts had a higher content of free than esterified phenolics, but the opposite was noted for winemaking byproducts. Insoluble-bound phenolics were up to 15 and 10 times more effective as antioxidants than those of free and esterified fractions, respectively, as evaluated by the DPPH, ABTS, and H 2 O 2 scavenging activities and reducing power determinations. In general, insoluble-bound phenolics (100 ppm) were more effective in inhibiting copper-induced human LDL-cholesterol oxidation than free and esterified phenolics, exhibiting equal or higher efficacy than catechin. Phenolic extracts from all fractions inhibited peroxyl radical-induced DNA strand breakage. These findings shed further light for future studies and industrial application of grape byproducts, which may focus not only on the soluble phenolics but also on the insoluble-bound fraction. KEYWORDS: processing byproduct, phenolic acids, flavonoids, proanthocyanidin, LDL-cholesterol, DNA ■ INTRODUCTION Fruits, vegetables, nuts, and cereals have been in the spotlight due to extensive literature support demonstrating their health benefits. Other than providing carbohydrate, protein, lipid, minerals, and vitamins, a balanced diet also provides a wide range of bioactive compounds. Polyphenols are recognized for rendering several health benefits such as potential anticancer, antimicrobial, and antioxidative effects. 1,2 However, commercial products have not always been considered as a viable source of bioactives. In this regard, several studies have demonstrated the high content of polyphenols in different commercial food products such as chocolate, tomato sauce, grape juice, and wine. The processing of foods and beverages generates a large amount of byproducts. The juice industry is one of the major suppliers of byproducts as a consequence of fruit seasonality as well as different climates and soil adaptation of the feedstock. Many tons of grapes are produced each year, and a large part of their final consumption is through grape juice and wine. Consequently, a considerable amount of byproducts (e.g., grape skin and seeds) is generated, creating an environmental burden. Several byproducts have been studied as a source of polyphenols, and the information available demonstrates their potential for being exploited. 3-5 Grape byproducts have also been shown to serve as a good source of dietary fiber 6 and for extending the shelf life of high-lipid foods due to their antioxidant activity. 7 The potential health benefits of such products/byproducts stems from their high polyphenol content, which has been evidenced by both in vitro and in vivo studies. 8,9 Polyphenols are water-soluble and found in the free, esterified, and insoluble-bound forms, the latter fraction being linked to the cell walls of source materials. Numerous studies have evaluated the phenolic profile, antioxidant properties, and potential biological activities of grapes and their byprod- ucts; 1,10,11 however, there are clear gaps in the existing knowledge about the contribution of the free, esterified, and insoluble-bound fractions to the total phenolic/polyphenolic contents that affect the antioxidant properties of grape byproducts. Moreover, grape byproducts are generated by both juice- and winemaking operations. The grape variety, its maturation stage, and crop production area are some of the crucial factors influencing the different phenolic profiles found in grape juice, wine, and their byproducts. Grape juice and winemaking have different processes, among them the fermentation process, which leads to alcohol generation, as the main one. For red wines, this stage is conducted in two steps called primary and secondary Received: August 31, 2014 Revised: November 12, 2014 Accepted: November 22, 2014 Published: November 22, 2014 Article pubs.acs.org/JAFC © 2014 American Chemical Society 12159 dx.doi.org/10.1021/jf504185s | J. Agric. Food Chem. 2014, 62, 12159-12171