Elsevier

Journal of Functional Foods

Volume 20, January 2016, Pages 332-345
Journal of Functional Foods

In vivo antioxidant activity of grape, pomace and wine from three red varieties grown in Argentina: Its relationship to phenolic profile

https://doi.org/10.1016/j.jff.2015.10.034Get rights and content

Highlights

  • Grape variety and winemaking affected phenolic profile and antioxidant capacity.

  • Phenolic compounds from samples modulate GPx and GR activities.

  • Syrah showed the highest AC due to its highest anthocyanin content.

  • Grapes showed the highest antioxidant capacity among sample types.

  • Pomace and wine had similar antioxidant capacity.

Abstract

The in vivo antioxidant capacity (AC) of natural antioxidants involved in the winemaking of three red grape varieties grown in Argentina and its association with the phenolic composition were studied. Polyphenols from grape, wine and pomace were capable of rescuing yeast cells from oxidative stress, probably by the induction of antioxidant enzymes, such as glutathione reductase (GR) and glutathione peroxidase (GPx). Observed AC was highly correlated with phenolic profiles, as shown by canonical correlation analysis (CCA) and multiple regression analysis (MRA). Grape samples showed the highest activity among sample types, and according to MRA kaempferol-3-glucoside and fertaric acid contributed positively, whereas ethyl gallate contributed negatively to AC of wines and pomaces. With respect to varieties, Syrah was the one with the highest activity, owing to higher contents of anthocyanins, compounds highly related to bioactivity.

Introduction

Epidemiologic studies provide convincing evidence that diets rich in plant foods (fruits, vegetables, grains and derivative products from fruits, vegetables and grains) are associated with the prevention or delay of chronic degenerative diseases, such as atherosclerosis, cancer, cardiovascular disease, and type 2 diabetes (Spormann et al., 2008). In the last decades oxidative stress has been proposed to play a fundamental role in these pathologies. The oxidative stress is defined as an imbalance between reactive oxygen species (ROS) production and the inability of the antioxidant biological system to detoxify these free radicals. As a result, this increased level of ROS leads cell to an oxidative stress state, which impacts on a variety of biochemical and physiological processes (Gutteridge & Halliwell, 2000).

In addition to vitamins and minerals, foods obtained from plant kingdom are rich in polyphenols, bioactive compounds capable of reducing the oxidative stress in cells. This biological property is mainly attributed to their behaviour as powerful antioxidants. Among the sources of exogenous natural antioxidants, grapes, grape pomace and wines from red varieties of Vitis vinifera L. have received much attention because of their high concentration and great variety of phenolic compounds.

Red grape polyphenols are mainly flavonoid (anthocyanins, flavonols and flavanols) and non-flavonoid compounds (phenolic acids like hydroxycinnamic and hydroxybenzoic acids and stilbenes), all of them are well known for their strong biological action (Monagas, Bartolomé, & Gómez-Cordovés, 2005). These compounds are transferred from the solid parts of the grape into the wine during winemaking operations (crushing, maceration and fermentation). The grape pomace is obtained from the winery industry as a solid waste after alcoholic fermentation, and it is mainly constituted by berry skins and seeds. This residue is characterised by a high phenolic content because of poor extraction during the winemaking process. Since about 80% of the worldwide grape production is used in winemaking and about 25% of the weight of processed grapes remains as pomace, the wine industry produces millions of tons of this residue, which represents an ecological and economical issue of waste management. Particular attention is currently being paid to the exploitation of this winery byproduct because it is considered an alternative and inexpensive source for obtaining natural phenolic compounds with potential application as food antioxidants (Fontana, Antoniolli, & Bottini, 2013).

Chemical antioxidant activity assays (such as FRAP-ferric reducing antioxidant power, TEAC-trolox equivalent antioxidant capacity) are used extensively to evaluate the potential bioactivity of plant foods, yet they do not mimic the complexity of biological systems. The cellular antioxidant activity assay was developed to be a more biologically relevant model to measure antioxidant activity. This approach reflects the cellular physiological conditions and considers the bioavailability and metabolism issues, which influence the net response of the phenolic compounds present in those samples. Among the cell culture models used to support antioxidant research prior to expensive and time-consuming animal studies and human clinical trials, the eukaryotic yeast Saccharomyces cerevisiae has been proposed for a rapid screening of AC in wine and food (Baroni et al, 2012, Ignea et al, 2013, López de Lerma et al, 2013, Martorell et al, 2011, Peinado et al, 2013, Stinco et al, 2015). Protective effect of polyphenols against oxidising substances in cells is related to a large number of biological mechanisms, including antioxidant enzyme induction such as superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) and glutathione peroxidase (GPx). These endogenous antioxidants are involved in the metabolism of glutathione (GSH), an important non-enzymatic antioxidant involved in cellular detoxification to maintain redox status (López-Alarcón & Denicola, 2013).

Nowadays, it is known that AC cannot be easily predicted by the content of a specific group of compounds or by measuring a single substance (Baroni et al., 2012). Furthermore, this activity is the result of a synergistic and antagonistic effect of different polyphenols and with other components of the food matrix or of the organism (Rohn, Rawel, & Kroll, 2004). Hence, we need to know the relative contribution of entire phenolic profile to the AC of these exogenous natural antioxidants in order to explain their bioactive behaviour. Accordingly, we propose the use of multiple regression analyses (MRA), a mathematical tool that quantifies the relationship between a dependent variable and twoor more independent variables. Furthermore, MRA allows determining the contribution of each variable to the model; thus, it allows us to identify the key phenolic compounds that contribute to the biological activity observed.

Phenolic profile is strongly affected both quantitatively and qualitatively by the particular grape variety, ripeness, environmental factors and winemaking technological procedure. Although there are a large number of studies that focus on polyphenols and their relationship with winemaking technology, understanding changes in phenolic profile has been always a challenge due to complexity and diversity of these compounds in red wines (Borazan & Bozan, 2013). Moreover, literature is scarce in terms of the association found/shown between these changes and the AC observed. Studies on the possible health benefits of grape and its derivates and on the mechanism underlying these benefits must be accompanied by a comprehensive characterisation of phenol profile.

In the present work we characterised the phenolic profile of grapes (raw material), pomaces (byproducts) and wines (final product) of three Vitis vinifera L. red varieties grown in Argentina, and assessed their AC by a cellular model in order to recognise the phenolic compounds associated with the bioactive behaviour of samples by MRA analysis. This work not only describes changes in phenolic profile and in vivo AC from grape to wine, but also studies one of the possible mechanisms by which polyphenols would be exerting their effect.

Section snippets

Samples

Vitis vinifera L. red grapes, grape pomace (skins and seeds) and red young wine, corresponding to three varieties (Syrah, Merlot and Cabernet Sauvignon), were obtained from the “Antonio de la Torre” cellar in the province of San Juan, Argentina. Three replicates of each sample type and variety were analysed. First, grapes were collected in their optimal ripening stage (22 to 25 g sucrose/100 mL). Pomaces were then collected after alcoholic fermentation and subsequent pressing, while young wines

Phenolic content of grape, pomace and wines

Table 1 shows the content of TP for each sample type of three V. vinifera L. red varieties. The TP ranged from 1062 to 1986 mg GAE g−1 DW for grapes in accordance with the results obtained by other authors (Lee, Rennaker, 2011, Meyer et al, 1997). This content showed significant differences among varieties. Cabernet Sauvignon and Syrah showed the highest and lowest content of TP among grape varieties, respectively. In the case of pomaces, all samples showed important content of TP, indicating

Conclusion

The results presented in this study underline differences in phenolic profile and in vivo antioxidant activity of products involved in the winemaking process: grape as a raw material, wine as a final product and pomace as a byproduct. In addition, we observed differences in both parameters according to the variety studied. Results from MRA analysis showed that Syrah had the highest AC, as a consequence of their phenolic profile characterised by the highest content in anthocyanin compounds,

Acknowledgements

We thank Agencia Nacional de Promoción Científica y Tecnológica (PICT 2008-0554) as well as Secretaría de Ciencia y Técnica-Universidad Nacional de Córdoba (05/C724) for financial support. We would like to express our gratitude to “Antonio de la Torre” cellar for providing samples.

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