Identification and characterization of proteolytically resistant gluten-derived peptides.

The lack of digestibility of certain gluten proteins is essential in the development of celiac disease (CD). Gluten proteins are remarkably resistant to luminal and brush-border proteolysis owing to their high proline and glutamine content. Consequently, large fragments remain intact after digestion exerting toxic effects. Intestinal brush-border membrane vesicles (BBMV) have been described as having strong proteolytic activity mainly through prolyl endopeptidase enzymes. The purpose of this work was to monitor the gastrointestinal digestion of specific CD epitopes by means of an in vitro gastrointestinal digestion model that included incubation with brush-border membrane enzymes. Gluten hydrolysates were characterized by mass spectrometry and the immunologic peptides were tracked by searching the main T-cell stimulating epitopes which have been widely described. The immunologic potential of gluten hydrolysates was further analysed by enzyme-linked immunosorbent assay (ELISA). The results showed that the composition of gluten hydrolysates depended on the digestion time and protein structural characteristics. On the other hand, the main T-cell stimulating epitopes formed during hydrolysis depend on the precursor protein. Glutenin oligopeptides were degraded faster whereas gliadin, mainly α-gliadin oligopeptides, remained intact for a long time. MS-based analysis showed that the formation of the epitopes from γ-gliadin and ω-gliadin or glutenin was favoured but they were generally degraded during the gastrointestinal treatment. However, the peptides containing the epitope PFPQPQLPY (α-gliadin) remained intact even after 180 min of digestion time. Overall, from all the epitopes tracked, PFPQPQLPY was the most resistant to in vitro BBMV digestion.

Chromatographic and mass spectrometry analysis of wheat flour prolamins, the causative compounds of celiac disease.

Immunogenic gluten peptides trigger Celiac Disease (CD), an adaptive immune response in genetically predisposed individuals. Given the structural similarity between all gluten proteins their individual CD influence is not clear. Hence, the extraction, separation and characterization of wheat gluten proteins have become relevant to measure their individual potential immunoreactivity. Wheat proteins were extracted from commercial wheat flour and further isolated by preparative HPLC. The resulting richest gliadin sub-fractions were characterized by nano-LC-MS/MS following a shotgun proteomic approach in order to identify the prolamins in the original commercial wheat flour. It was found that the gliadin extract was additionally composed of glutenins and avenin-like proteins. Accurate prolamin identification has emerged as a need to delve deep into the influence of each fraction on the onset of celiac disease. After protein characterization, the immunoreactivity towards the main epitope related to CD was verified by ELISA and western blotting for several different gluten fractions.

Rapid screening and identification of new soluble tannin-salivary protein aggregates in saliva by mass spectrometry (MALDI-TOF-TOF and FIA-ESI-MS).

Astringency is mainly attributed to the interaction between tannins and salivary proteins. Proline-rich proteins, histatins, and statherins are supposed to be the most reactive salivary proteins. This study aims to contribute to the knowledge of the tannin-protein binding process in saliva. It was identified for the first time in several soluble tannin-human salivary protein aggregates. A rapid mass spectrometry analytical method (MALDI-TOF and FIA-ESI-MS) was developed to identify new soluble tannin-human salivary protein aggregates. Three different tannins--procyanidin B3 (B3), procyanidin B2 gallate (B2G), and pentagalloylglucoside (PGG)--were tested to elucidate the tannin selectivity toward histatins, proline-rich proteins, and statherins in human saliva. A greater number of aggregates with a higher molecular weight was found when PGG was tested while no difference in the number and molecular mass range was observed in B3 or B2G salivary protein aggregates. This study confirms for the first time the bilateral selectivity of tannins and protein to yield soluble tannin-human salivary protein complexes. The results confirm that B3 and B2G are more selective than PGG. Furthermore, the families of proteins involved in the majority of B3-salivary protein soluble aggregates were primarly histatins, followed by basic proline-rich proteins and statherins. When B2G was tested, basic proline-rich proteins were involved in a greater number of aggregates, followed by histatines and statherins. Basic proline-rich proteins were also the family of proteins that formed a greater number of PGG-salivary protein aggregates followed by statherins and histatins. Acidic proline-rich proteins and glucosilated proline-rich proteins formed fewer soluble aggregates regardless of the tannin tested. The aggregation process was also found to be influenced by tannin and protein polarity. Indeed, the protein/tannin ratio of soluble aggregates increased with the tannin polarity. On the other hand, the only amphiphilic salivary proteins studied (histatins) formed a greater number of aggregates with the least polar tannin tested (B3).

Increasing the added-value of onions as a source of antioxidant flavonoids: a critical review.

Flavonoids are a large and diverse group of polyphenolic compounds with antioxidant effects. While the flavonoid content and composition profile clearly reflect the genetic background of the cultivar, environmental conditions and agronomic practices are also determinants for the composition of crops at harvest. Considerable research has been directed toward understanding the nature of polyphenols in different products and the factors influencing their accumulation. This review examines the flavonoids as a class of compounds, the role these compounds play in the plant, their contributions to product quality, and recent research on the impacts of environmental factors and cultural practices on flavonoid content in onions, highlighting how this knowledge may be used to modulate their polyphenolic composition at harvest or during post-harvest handling.

Removal of polycyclic aromatic hydrocarbons from organic solvents by ashes wastes.

Polycyclic aromatic hydrocarbons (PAHs) can be formed during the refinery processes of crude petroleum. Their removal is of great importance. The same happens with other organic solvents used for the extraction of PAHs (hexane, acetonitrile...), which can be polluted with PAHs. Kinetic and equilibrium batch sorption tests were used to investigate the effect of wood ashes wastes as compared to activated carbon on the sorption of three representative PAHs from n-hexane and acetonitrile. Mussel shell ashes were discarded for batch sorption experiments because they were the only ashes containing PAHs. The equilibrium time was reached at 16 h. Physical sorption caused by the aromatic nature of the compounds was the main mechanism that governed the PAHs removal process. Our investigation revealed that wood ashes obtained at lower temperature (300 degrees C) did not show any PAHs sorption, while ashes obtained at higher temperature (>500 degrees C) have adsorbent sites readily available for the PAH molecules. An increase in the molecular weight of PAHs has a strong effect on sorption wood ashes wastes. As low the wood ashes particle size as high the sorption of PAHs, as a result of differences in adsorbent sites. The performance of wood ash wastes vs. activated carbon to remove 10 PAHs from organic solvents is competitive in price, and a good way for waste disposal.