Preliminary screening of the Malagasy plant Combretum albiflorum for compounds attenuating the production of quorum sensing (QS)-controlled virulence factors in bacteria led to the identification of active fractions containing flavonoids. In the present study, several flavonoids belonging to the flavone, flavanone, flavonol and chalcone structural groups were screened for their capacity to reduce the production of QS-controlled factors in the opportunistic pathogen Pseudomonas aeruginosa (strain PAO1). Flavanones (i.e. naringenin, eriodictyol and taxifolin) significantly reduced the production of pyocyanin and elastase in P. aeruginosa without affecting bacterial growth. Consistently, naringenin and taxifolin reduced the expression of several QS-controlled genes (i.e. lasI, lasR, rhlI, rhlR, lasA, lasB, phzA1 and rhlA) in P. aeruginosa PAO1. Naringenin also dramatically reduced the production of the acylhomoserine lactones N-(3-oxododecanoyl)-Lhomoserine lactone (3-oxo-C12-HSL) and N-butanoyl-L-homoserine lactone (C4-HSL), which is driven by the lasI and rhlI gene products, respectively. In addition, using mutant strains deficient for autoinduction (DlasI and DrhlI) and LasR-and RhlR-based biosensors, it was shown that QS inhibition by naringenin not only is the consequence of a reduced production of autoinduction compounds but also results from a defect in the proper functioning of the RlhR-C4-HSL complex. Widely distributed in the plant kingdom, flavonoids are known for their numerous and determinant roles in plant physiology, plant development and in the success of plant-rhizobia interactions, but, as shown here, some of them also have a role as inhibitors of the virulence of pathogenic bacteria by interfering with QS mechanisms. INTRODUCTIONIn many pathogenic bacteria the production of virulence factors is triggered in a population density-dependent manner through quorum sensing (QS), a cell-to-cell communication mechanism that enables bacteria to coordinate virulence factor production by means of the synthesis, release and perception of small diffusible molecules called autoinducers (Antunes et al., 2010;Bjarnsholt et al., 2010;Case et al., 2008;Ng & Bassler, 2009). For instance, in the plant and mammal opportunistic pathogen Pseudomonas aeruginosa, two main QS systems (lasI/R and rhlI/R), responsible for the synthesis and perception of the acylhomoserine lactones (AHLs) N-(3-oxododecanoyl)-L-homoserine lactone (3-oxo-C12-HSL) and N-butanoyl-L-homoserine lactone (C4-HSL), respectively , control the expression Abbreviations: AHL, acylhomoserine lactone; C4-HSL, N-butanoyl-Lhomoserine lactone; ESI-MS, electrospray ionization-MS; HHL, Nhexanoyl-L-homoserine lactone; 3-oxo-C12-HSL, N-(3-oxododecanoyl)-L-homoserine lactone; PI, propidium iodide; QS, quorum sensing.3These authors contributed equally to this work. of an arsenal of virulence factors. The transcription factors LasR and RhlR interact with and are activated by 3-oxo-C12-HSL and C4-HSL, respectively, triggering the production of biofilms, LasB elastase...

Cocoa bean shells (CBS) are one of the main by-products from the transformation of cocoa beans, representing 10%‒17% of the total cocoa bean weight. Hence, their disposal could lead to environmental and economic issues. As CBS could be a source of nutrients and interesting compounds, such as fiber (around 50% w/w), cocoa volatile compounds, proteins, minerals, vitamins, and a large spectrum of polyphenols, CBS may be a valuable ingredient/additive for innovative and functional foods. In fact, the valorization of food by-products within the frame of a circular economy is becoming crucial due to economic and environmental reasons. The aim of this review is to look over the chemical and nutritional composition of CBS and to revise the several uses that have been proposed in order to valorize this by-product for food, livestock feed, or industrial usages, but also for different medical applications. A special focus will be directed to studies that have reported the biofunctional potential of CBS for human health, such as antibacterial, antiviral, anticarcinogenic, antidiabetic, or neuroprotective activities, benefits for the cardiovascular system, or an anti-inflammatory capacity.

Hence, it is critical that toxicologists in industry, regulatory agencies and academic institutions develop a consensus, based on rigorous methods, about the reliability and interpretation of endpoints. It will also be important to regulate the integration of conventional methods for toxicity assessments with new "omics" technologies.

One of the main by-products in cocoa industry is the cocoa bean shell (CBS), which represents approximately 12–20% of the bean. This product has been suggested as a food ingredient because of its aroma and high dietary fiber and polyphenol contents. The purpose of this work was to evaluate the effects of the CBS particle size and extraction methods on the chemical composition and consumer acceptance of a functional beverage, in order to find the best combination of technological parameters and health benefits. Five particle sizes of CBS powder and six home techniques were used for beverage preparation. The influence of these factors on the physico-chemical characteristics, methylxanthine and polyphenolic contents, antioxidant and antidiabetic properties, and consumer acceptance was evaluated. Total phenolic content values up to 1803.83 mg GAE/L were obtained for the beverages. Phenolic compounds and methylxanthines were identified and quantified by HPLC-PDA. These compounds may be related to the high antioxidant capacity (up to 7.29 mmol TE/L) and antidiabetic properties (up to 52.0% of α-glucosidase inhibition) observed. Furthermore, the consumer acceptance results indicated that CBS may represent an interesting ingredient for new functional beverages with potential health benefits, reducing the environmental and economic impact of by-product disposal.

International audienceThe leaves of three Mentha species harvested in Algeria, Mentha spicata L. (MS), Mentha pulegium L. (MP) and Mentha rotundifolia (L.) Huds (MR) were examined for their content in polyphenols and for some activities-linked biological properties these could impart. The contents in total phenolics (TPC) and flavonoids (TFC) were evaluated by the Folin–Ciocalteu and the aluminum chloride methods, respectively. Whereas MS showed the highest TPC (12.0 ± 0.3 mg gallic acid equivalents/g of dry weight), MR had the highest content in TFC (3.3 ± 0.1 mg quercetin equivalents of dry weight). The pharmacological properties of these extracts were evaluated by assessing in vitro their antioxidant and antityrosinase activities. The modulation of mushroom tyrosinase activity was measured by colorimetry of the melanins formed in the presence of tyrosine. MS exhibited the strongest radical scavenging activity (RSA) in all assays: (i) the IC50s values to neutralize the 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) cation radicals (ABTS+) and the 2,2′-diphenyl-1-picrylhydrazyl radicals (DPPH) were 10.3 ± 0.9 and 16.2 ± 0.2 μg/mL, respectively; and (ii) its original electrochemically measured superoxide quenching index value is 188 ± 37 μg/mL (AI50). MR however showed the highest tyrosinase inhibitory activity (IC50 = 108 ± 20 μg/mL). A silica gel thin-layer chromatography (TLC) technique revealed the presence of caffeic and rosmarinic acids and diosmin in all extracts. These results were confirmed by high performance liquid chromatography with diode array detection (HPLC/DAD