Elsevier

Food Chemistry

Volume 348, 30 June 2021, 129063
Food Chemistry

Assessment of in-vitro bioaccessibility and antioxidant capacity of phenolic compounds extracts recovered from grapevine bunch stem and cane by-products

https://doi.org/10.1016/j.foodchem.2021.129063Get rights and content

Highlights

  • In-vitro digestion effects on PCs and AC of grapevine woody by-products was studied.

  • Bioaccessibility of PCs from grape cane extract was assessed for the first time.

  • PCs from cane and bunch stem extracts were 74 and 20% bioaccessible, respectively.

  • The stilbene ε-viniferin in cane extract was 137% bioaccessible.

  • Total PCs and AC values of extracts and their digests were positively correlated.

Abstract

Grapevine woody by-products contain bioactive substances, mainly phenolic compounds (PCs), whose beneficial health effects initially depends on their levels of intake and bioavailability. Therefore, in-vitro simulated gastrointestinal digestion (GID; oral, gastric and intestinal phases) was performed to evaluate the bioaccessibility and antioxidant capacity (AC) of PCs extracts recovered from grapevine bunch stem and cane from Malbec grape cultivar. The total PCs in cane and bunch stem extracts were 74 and 20% bioaccessible, respectively. Syringic acid, cinnamic acid, ε-viniferin, naringenin and myricetin were highly bioaccessible, noticeably ε-viniferin in cane extract with 137%. The high bioaccessibility observed, particularly for compounds at high concentration such as ε-viniferin, will help to better understand the bioactive potential of these by-products. In this sense, bunch stems and canes can be considered as new and sustainable sources of bioactive substances for applications as functional ingredients or nutraceuticals in food and pharmaceutical industries.

Introduction

Every year, viticulture produces more than 70 million tons of berries coming from a worldwide cultivated area of 7.5 million ha (International Organization of World Vitiviniculture (OIV), (2017)). This agro-economic activity produces a significant volume of grapevine woody derivatives, such as bunch stems and canes, which constitutes potential sources of a wide range of phenolic compounds (PCs) with purported biotechnological applications. Canes are the result of a management practice on grapevine plants performed every year and aimed to prune the plants for improving grapes yield stability and quality of berries. This activity generates an average amount of roughly 2.5 tons per ha per year (Ferreyra, Antoniolli, Bottini, & Fontana, 2020). Bunch stems are the other lignocellulosic by-product that accumulate along the winemaking process and constitutes 5% of the processed grapes at harvest time (Ferreyra, Bottini, & Fontana, 2019). Normally, these grapevine derivatives are composted or burned thus limiting their potential application as a font of bioactive compounds for food, pharmaceutical and cosmetic industries.

Recently, the study of grapevine residues has been increased due to their potential as source of health-promoting bioactive compounds. Antioxidant, cardio-protective, anti-inflammatory, anti-microbial, anti-fungal, anti-aging and anti-cancer properties have been reported (Barros et al., 2015, Teixeira et al., 2014). Most researches are focused on the study of PCs (flavonoids, phenolic acids and stilbenes) and dietary fiber together with other minor compounds which allows assessing nutritional quality of these wastes (Çetin et al., 2011, González-Centeno et al., 2010). Although there is an overall trend in the phenolic profiles of these by-products in grapevine, levels of individual PCs depend on plant variety and phenology, environmental growth conditions, vineyards management, and winemaking process (Ferreyra et al., 2020, Ferreyra et al., 2019).

Previous reports showed that grape cane extracts are characterized by high levels of stilbenes, particularly ε-viniferin (Ferreyra et al., 2020, Guerrero et al., 2016, Lambert et al., 2013), although other oligomeric derivatives have been also reported (Pešić et al., 2019). ε-viniferin has remarkable valuable health properties, conspicuously for its cardio-protective and antioxidant functions in comparison to trans-resveratrol (Sáez et al., 2018, ZGHONDA et al., 2012). Although previous reports informed that ε-viniferin has difficulties in passing the intestinal barrier and to be metabolized as compared with trans-resveratrol, it may act locally on the gastrointestinal tract (Willenberg, Michael, Wonik, Bartel, Empl, & Schebb, 2015). During an in-vitro assay, ε-viniferin exhibited stronger inhibitory potential of intestinal glucose uptake than trans-resveratrol (Guschlbauer, Klinger, Burmester, Horn, Kulling, & Breves, 2013). Besides of the potential bioactivity of ε-viniferin, there are no studies reporting its digestive stability and bioavailability. In the case of bunch stem extracts, flavanols, flavonols and phenolic acids have been reported as the main constituents (Barros et al., 2015, Goufo et al., 2020). In this matrix, the strong antioxidant activity is due to their high levels of (+)-catechin, which protect macromolecules from the action of free radicals (Barros et al., 2015). In turn, the hydro-methanolic extracts of grape stems have also been shown inhibition of the growth of foodborne pathogens including E. coli and Salmonella sp. (Barros et al., 2015).

To perform a positive biological function in the organism, bioactive compounds or moieties from them must be bioavailable, that is, digested and efficiently assimilated. Therefore, to understand the potential health benefits of novel grapevine by-products it is essential the investigation of the digestion effect on the PCs bioaccessibility (Lorenzo et al., 2019). It is known that bioaccessibility differs from one compound to another, even from the same family, due to the influence of chemical structure, like type and native form in which they are found in the ingested matrix (Manach, Williamson, Morand, Scalbert, & Rémésy, 2005). The in-vitro simulated gastrointestinal digestion (GID) allows to study the bioavailability of compounds concerning their potential for intestinal absorption (Haas et al., 2019, Tagliazucchi et al., 2010). During this process, the bioactive components can be retained inside their matrix or released into intestinal fluids remaining stable or changing into other compounds. Thereby, digestion process can change the profile of bioactive compounds in certain product and thus its properties, such as the overall AC. Currently, in-vitro digestion is the most employed methodology in studies of bioavailability. This in-vitro method is safer, faster and cheaper than other in-vivo approaches, and also has no ethical restrictions (Hur, Lim, Decker, & McClements, 2011). As an additional characteristic, the in-vitro methods are specially designed for initial screening of the compounds performance in different matrices, in complementation with in-vivo studies. However, only few researches have studied the effect of GID on the chemical composition and the bioactivity of some winemaking by-products in the past years (Corrêa et al., 2017, Garbetta et al., 2018, Laurent et al., 2007, Sanz-Buenhombre et al., 2016, Tagliazucchi et al., 2010). Most of them have been focused on grape pomace extracts. A low number of studies about woody by-products, specifically for bunch stems have been reported (Jara-Palacios et al., 2018, Li et al., 2019). So far, there are not reports on bioaccessibility of PCs recovered from grape cane extracts for any variety, nor for bunch stem extracts from cv. Malbec have been published.

The present work is aimed to evaluate the effect of digestion process upon bunch stem and grape cane extracts of the Malbec variety, the most cultivated Vitis vinifera of Argentina. As well, to establish the bioaccessibility of recovered PCs and AC variations throughout the digestive phases. With the objective to mimic the digestive process in the mouth, stomach (gastric digestion) and small intestine (duodenal digestion), a three-step procedure was performed. Before digestion and after each step, the stability of individual PCs was evaluated by LC-DAD. Moreover, the total phenolic content (TPC) and the in-vitro AC were determined by ABTS and ORAC methods.

Section snippets

Reagents and standards

Standards of gallic acid (99%), syringic acid (≥95%), cinnamic acid (99%), caftaric acid (≥97%), p-coumaric acid (98%), trans-resveratrol (≥99%), (+)-ε-viniferin (≥95%), procyanidin B1 (≥90%), procyanidin B2 (≥90%), (+)-catechin (≥99%), (−)-epicatechin (≥95%), (−)-gallocatechin (≥98%), (−)-gallocatechin gallate (≥99%), (−)-epigallocatechin gallate (≥95%), naringin (≥95%), naringenin (≥95%), astilbin (≥98), quercetin 3-β-d-glucoside (≥90%), quercetin 3-β-d-galactoside (≥97%), myricetin (≥96%),

Effect of in-vitro digestion of Malbec cane and bunch stem extracts on the total bioaccessibility of PCs

The RI of total PCs quantified by LC-DAD (expressed as the sum of individual compounds) after each GID step for bunch stem and cane extracts is shown in Fig. 1. The RI was calculated using Eq. (1) presented in section 2.6 and the IP value obtained corresponds to the percentage of bioaccessibility. For bunch stem extracts, the PCs were relatively stable in the OP, although a decreasing trend was found as the digestive process progressed. Otherwise, the PCs of cane extracts showed an increasing

Conclusions

The current study stated the effect of in-vitro GID on the phenolic profile and AC of bunch stem and cane extracts of the Malbec variety. Both matrices showed different results in terms of bioaccessibility. Furthermore, phenolic profile and RI of PCs were differently affected by each digestion phase. The TPC and AC of extracts and their digested fractions showed a similar behavior than phenolic profile and a direct association of these variables was observed. Additionally, the levels of PCs

CRediT authorship contribution statement

Susana Ferreyra: Conceptualization, Methodology, Investigation, Formal analysis, Data curation, Writing - original draft, Writing - review & editing. Carolina Torres-Palazzolo: Methodology, Formal analysis, Writing - review & editing. Rubén Bottini: Supervision, Writing - review & editing. Alejandra Camargo: Supervision, Writing - review & editing. Ariel Fontana: Conceptualization, Methodology, Formal analysis, Investigation, Resources, Data curation, Visualization, Supervision, Project

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work was supported by ANPCyT (Grant number: BID PICT 2017-2325) and SIIP-UNCuyo to A.F. Additionally, we received the support from CONICET (Grant number: PUE 2016-124). S.F. and C.T.P have a CONICET scholarship; R.B., A.C. and A.F. are fellows of CONICET. The authors are also grateful to Roy Urvieta for providing the samples.

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