Potential bioaccessibility and functionality of polyphenols and cynaropicrin from breads enriched with artichoke stem
Introduction
Globe artichoke (Cynara cardunculus L. var. scolymus) is a widely cultivated crop in the Mediterranean regions. Italy is the first world producer (451,461 tons/year) followed by Egypt (266,196 tons/year) and Spain (234,091 tons/year) (FAO, 2014). The immature inflorescence (capitula or head) represents the edible part of the plant and is consumed as fresh, frozen, or canned food (de Falco, Incerti, Amato, & Lanzotti, 2015). Stems and external leaves represent about 80–85% of the total fresh weight of the plant and are the most abundant by-products from industrial processing of artichoke (Lattanzio, Kroon, Linsalata, & Cardinali, 2009).
Both edible fractions and artichoke by-products are well known sources of dietary fiber (DF) and polyphenols (PPs), mainly including caffeoylquinic acids (CQA), di-caffeoylquinic acids (DCQA) and flavones (Femenia et al., 1998, Lattanzio et al., 2009, Pandino et al., 2013). Chlorogenic acid (5-O-caffeoylquinic acid), 1,5-di-O-caffeoylquinic acid, 3,4-di-O-caffeoylquinic acid and 3,5-di-O-caffeoylquinic acid are the most abundant phenolic acids in artichoke tissues, whereas luteolin and apigenin glycosides and rutinosides derivatives are the most abundant flavones (Lattanzio et al., 2009). These molecules exert in vitro antioxidant, antimicrobial and anticancer activities and act as natural inhibitors of key enzymes involved in metabolic syndrome development (de Falco et al., 2015, Matsui et al., 2006, Villiger et al., 2015). Several human studies demonstrated that the health benefits associated with the intake of artichoke bioactive compounds, mainly include antioxidative, hypolipidemic, hypoglycemic, anti-inflammatory, and anti-obesity effects (Rondanelli et al., 2011, Rondanelli et al., 2015, Rondanelli et al., 2014). Those effects are due to the ability of artichoke phenolics to modulate cellular antioxidant defence systems and some crucial enzymatic pathways.
Sesquiterpene lactones (guaianolides) are another abundant class of compounds present in artichoke, mainly in external leaves. They are associated with several biological properties, such as anti-hyperlipidemic, anti-inflammatory and anti-photoaging activities (de Falco et al., 2015). Cynaropicrin is the most abundant guaianolide, accounting for the 80% of the typical bitter taste of artichoke (Cravotto, Nano, Binello, Spagliardi, & Seu, 2005). At very low concentrations, cynaropicrin and grosheimin can activate in vitro the human bitter taste receptor hTAS2R46 (Brockhoff, Behrens, Massarotti, Appendino, & Meyerhof, 2007). This property may contribute to the metabolic benefits mostly associated to the consumption of artichoke DF and PPs. Indeed, mounting evidence shows that bitter compounds modulate neurohormonal response behind gastrointestinal motility, glucose homoeostasis and appetite control through the activation of bitter taste receptors located along the gastrointestinal tract (GiT) (Mennella et al., 2016).
The multitude of bioactive compounds in artichoke by-products make them a good source of ingredients useful to enhance the antioxidant activity and the functional properties of wheat bread, as already proposed by some researchers (Boubaker et al., 2016, Frutos et al., 2008). Despite the undisputable social value to valorize agricultural by-products, their use as new functional food ingredients needs a bio-efficacy validation inside the food. In fact, food processing as well as food structure influence the chemical composition and the bioavailability of bioactive compounds from the enriched-food products (Dziki, Różyło, Gawlik-Dziki, & Świeca, 2014).
The bioaccessibility, the bioavailability and the potential antioxidant effects along the GiT of PPs from artichoke heads, were previously investigated both in vivo and in vitro (Azzini et al., 2007, D’Antuono et al., 2015). Scientific literature is still lacking on the bioaccessibility and potential bio-efficacy of bioactive compounds from foods enriched with artichoke by-products.
In this study, artichoke stems were selected among artichoke by-products and added at 3%, 6% and 9% in the formulation of new types of bread. Potential bioaccessibility of PPs and cynaropicrin from the breads as well as overall total antioxidant capacity (TAC) and potential ability to modulate α-glucosidase activity in the GiT were assessed.
Section snippets
Chemicals
Water, methanol and acetonitrile were obtained from Merck (Darmstadt, Germany). Ethanol and formic acid were purchased from VWR international (Fontenay-sous-Bois, France). Cellulose powder was obtained from Fluka (Buchs, Switzerland). Total dietary fiber assay kit was purchased from Megazyme International (Wicklow, Ireland). Calcium chloride, potassium chloride, sodium chloride, potassium phosphate monobasic, magnesium chloride hexahydrate, ammonium carbonate,
Characterization of the artichoke by-products and nutritional composition of breads
In Table 2 the content of DF, total PPs and cynaropicrin as well as the antioxidant capacity of the artichoke by-products (leaves and stem) in comparison to the head, is reported. ASP showed the highest amount of total PPs and the highest AC compared to other artichoke fractions. Total PPs of ASP was 1.6 and 3.9 folds higher than artichoke leaves powder (ALP) and artichoke head powder (AHP), respectively. According to the amount of total PPs, the AC was 1.6 and 4.7 folds higher for ASP than ALP
Discussion
In this study the artichoke stem was used as food ingredient in bread formulation and the bioaccessibility of PPs and cynaropicrin, the overall TAC and the ability of the breads to inhibit α-glucosidase in the intestinal tract were tested in vitro. Artichoke stem was selected as promising functional ingredient for its content of DF and PPs. Data showed that ASP had a higher amount of total PPs (mainly including phenolic acids) and AC, as well as a more balanced IDF/SDF ratio than the artichoke
Conclusion
In this study an ASP was used as food ingredient in the formulation of new breads. Data showed that the potential release of PPs and cynaropicrin as well as antioxidant and α-glucosidase activities in the small intestine were proportional to the amount of ASP added to the bread recipe. Interestingly, part of these bioactive compounds were potentially released in the step simulating colon digestion thus suggesting an effect of the new foods that may be mediated by the intestinal microbiota in an
Conflict of interest
The Authors declare no conflict of interest.
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