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International audience; Aim: Polyphenols, dietary compounds, have drawn increasing attention due to their ability to lower oxidative stress involved in many pathologies and due to their positive effects in modulation of redox cellular signalling pathways [1]. The objectives of our studies are to identify the compounds derived from polyphenols after cellular metabolization (neuronal cells and gut bacteria) and to highlight how these molecules can act beneficially on microbiota and prevent neurodegenerescence diseases [2]. A particular attention is paid on oxidized phenolic metabolites and their biological effects. Methods: Currently, we focus our work in the impact of 5-O-caffeoylquinic acid (5-CQA), a dietary phenolic compound with neuroprotective properties [3], on the growth and the metabolism of three intestinal bacterial species (Lactobacillus reuteri, Bacteroides fragilis and Bifidobacterium longum). In parallel, we determine the bioconversion of 5-CQA by these three bacteria in mono and co-cultures. We particularly use LC-ESI-MS 2 and a molecular networking approach (GNPS platform) [4] to identify the biotransformed metabolites (e.g. oxidized derivatives). In addition, electrochemical technics are helpful to study the redox mechanism of 5-CQA and to generate oxidized samples. Results: L. reuteri has shown capacity to biotransform 5-CQA notably into caffeic acid and its oxidized derivative quinone, and into 3-hydroxybenzoic acid, contrary to B. fragilis and B. longum which didn't show any ability. First experiments in co-cultures were also carried out. Conclusion and perspectives: We have demonstrated an oxidative pathway in the bioconversion of 5-CQA by L. reuteri. Further experiments will be carried out to show the role of native, oxidized and biotransformed dietary polyphenols in the gut-brain axis.

International audience

International audience; Apple polyphenols are considered to have protective effects against different diseases and especially against cardiovascular diseases. A recent dose-response meta-analysis showed that the risk of coronary heart disease mortality is reduced by 25% for people consuming 200 mg/day of flavonoids [1]. However, increasing polyphenols in food may also enhance bitterness and astringency (2) that might result in low acceptability. Especially, limiting the losses during processing or adding polyphenols extracted from vegetables by-products often enhance this detrimental effect because these process usually increase high polymerized procyanidins content. Another way is to use bitter apple having naturally high polyphenol content and to accept mash oxidation and maceration that lead to a selective loss of those high-polymerized procyanidins (3). Comparing the detailed polyphenol composition of most of commercial juices with experimental juices made from French cider apple, we showed that the experimental juices could be ten time higher than the mean commercial juices. When produced under anaerobic conditions the juices of bitter varieties were rejected due to their astringency but when produced by an oxidative process, acceptance clearly increased to reach mean scores. However the taste was often considered “unusual” probably due to bitterness and low acidity.Juices containing more than 5 g/L of polyphenols could be considered as extremes but cider apples can also be used to produce realistic juices by mixing with more conventional apple juices. A wide range of polyphenol content and acidity was obtained by mixing the juices of three contrasted varieties (acidic, bitter and a bitter-sweet). Ten juices, defined by a mixing design, were then tested for their acceptability by French consumers. The results showed that juices up to 2.5 g/L of total polyphenols (ic 1.3 g/L of flavonoids) ranged among the preferred juices and scored as high as acidic juices that are close to classical commercial juices. Moreover, as pale juices are preferred in a many countries, consumers were also asked about juices colour. For a large majority of them the orange/yellow colour due to polyphenols oxidation was well accepted by French consumers.Given the total polyphenol content of these preferred juices, one serving of 200 ml per day could be enough to ensure 200 mg/day of flavonoids that can be considered as an active intake (reducing mortality). At this level the sugar intake remains acceptable for most consumers.

International audience; This study provides a detailed characterisation of a leaf protein concentrate (LPC) extracted from Cichorium endivia leaves using a pilot scale process. This concentrate contains 74.1% protein and is mainly composed of Ribulose-1,5-BISphosphate Carboxylase/Oxygenase (RuBisCO). We show that the experimentally determined extinction coefficient (around 5.0 cm−1 g−1 L depending on the pH) and refractive index increment (between 0.27 and 0.39 mL g−1) are higher than the predicted ones (about 1.6 cm−1 g−1 L and 0.19 mL g−1, respectively). In addition, the UV–visible absorption spectra show a maximum at 258 nm. These data suggest the presence of non-protein UV-absorbing species. Chromatographic separation of the concentrate components in denaturing conditions suggests that RuBisCO SC may be covalently bounded to few phenolic compounds. Besides, the solubility of LPC proteins is higher than 90% above pH 6. Such high solubility could make LPC a good candidate as a functional food ingredient.

International audience; Dehydrodicaffeoylquinic acids (DDCQAs) are among the main phenolic products resulting from enzymatic oxidation occurring during apple processing. Accounting for dozen milligrams per liters in some apple juices, they present original chemical structures including benzodioxane, dihydronaphtalene, dihydrobenzofuran or dicatechol patterns. Interestingly, those oxidation products exhibited unusual properties regarding their ability to aggregate salivary proteins.

International audience; Condensed Tannins are of great interest in organoleptic properties of apple-based beverages, particularly due to their oxidation caused by technologic processes. To better understand the impact of oxidation of procyanidins on astringency sense and quantify oxidation products, it was necessary to isolate tannins from raw materials, for model-solution studies. A gentle strategy combining pH-zone-refining centrifugal partition chromatography (pH-ZRCPC) and preparative reversed-phase liquid chromatography (Prep-RPLC) was developed to recover the main phenolic compounds families separately, from 1 g apple crude extract. First, a pH-ZRCPC fractionation was optimized to remove hydroxycinnamic acids, with a biphasic mixture composed of ethyl acetate-n-butanol-water (3:2:5) in descending mode. Trifluoroacetic acid (10 mM) and sodium hydroxide (10 mM) were used as retainer and eluter, in the upper and lower phases, respectively. Secondly, easy Prep-RPLC separation was carried out in isocratic mode at 20% ACN to discard dihydrochalcones. Finally, 409 mg of a highly purified tannin extract with a mean degree of polymerisation of 5.5 was obtained with a recovery of 100%.