Investigation of immunogenic gluten peptides: identification using enzymatic tagging and HPLC-MSn; analysis and quantification using HPLC-MS/MS

The goal of my research was to provide some insight into a widely appreciated but poorly understood relationship between cereal grain proteins and human health. My research objectives were: (1) to identify and characterize inflammatory, physiologically relevant, wheat gluten peptides and (2) to develop a unique analytical methodology to screen commercially available food and consumer products for the quantitative detection of these peptides. Gluten proteins comprise a very large protein family found in cereal grain seeds. This large protein family consists of hundreds of proteins ranging in size from about 30 kDa into the millions of KDa. Today's nomenclature refers to gluten as the water-insoluble seed storage proteins found in the Triticeae tribe of the grass (Gramineae) family that includes wheat, rye and barley. Some gluten proteins associated with grains in the Triticeae tribe (specifically: wheat, rye and barley), have been implicated in various autoimmune diseases, food allergies, intolerances and are important factors in several inflammatory diseases. Many analytical techniques have been used to study gluten proteins and peptides. Unambiguous identification and structural characterization of such peptides is a necessary step toward an eventual understanding of their chemical biology. Liquid chromatography-mass spectrometry (LC-MS) is an extremely powerful tool for such analyses. Results of my research are presented here, in the following chapters of this thesis report. Data presented supports the development of a novel and effective analytical methodology, using enzymatic/chemical labeling chemistry and HPLC/MSn; to identify and characterize seven physiologically relevant wheat gluten peptides. A sensitive and specific assay was then developed for the quantitative detection of these peptides via direct in-vitro proteolytic digestion and HPLC-MS/MS. This versatile methodology allows both processed and native foods, as well as consumer products, to be analyzed for the presence of wheat gluten. Continued efforts in this area will pave the way for eventual commercial application, as a service to both the celiac community and the food industry, by providing an accurate and economic means to generate much needed data for researchers developing treatments for patients with gluten sensitivities and manufacturers producing and labeling products that are safe

CYP1A1 and CYP1B1-mediated biotransformation of the antitrypanosomal methamidoxime prodrug DB844 forms novel metabolites through intramolecular rearrangement

DB844 (CPD-594-12), N-methoxy-6-{5-[4-(N-methoxyamidino)phenyl]-furan-2-yl}- nicotinamidine, is an oral prodrug that has shown promising efficacy in both mouse and monkey models of second stage human African trypanosomiasis. However, gastrointestinal (GI) toxicity was observed with high doses in a vervet monkey safety study. In the current study, we compared the metabolism of DB844 by hepatic and extrahepatic cytochrome P450s to determine if differences in metabolite formation underlie the observed GI toxicity. DB844 undergoes sequential O-demethylation and N-dehydroxylation in the liver to form the active compound DB820 (CPD-593-12). However, extrahepatic CYP1A1 and CYP1B1 produced two new metabolites, MX and MY. Accurate mass and collision-induced dissociation mass spectrometry analyses of the metabolites supported proposed structures of MX and MY. In addition, MY was confirmed with a synthetic standard and detection of nitric oxide release when DB844 was incubated with CYP1A1. Taken altogether, we propose that MX is formed by insertion of an oxygen into the amidine C=N to form an oxaziridine, which is followed by intramolecular rearrangement of the adjacent O-methyl group and subsequent release of nitric oxide. The resulting imine ester, MX, is further hydrolyzed to form MY. These findings may contribute to furthering the understanding of toxicities associated with benzamidoxime- and benzmethamidoxime-containing molecules

CYP1A1 and CYP1B1-Mediated Biotransformation of the Antitrypanosomal Methamidoxime Prodrug DB844 Forms Novel Metabolites Through Intramolecular Rearrangement

DB844 (CPD-594-12), N-methoxy-6-{5-[4-(N-methoxyamidino)phenyl]-furan-2-yl}-nicotinamidine, is an oral prodrug that has shown promising efficacy in both mouse and monkey models of second stage human African trypanosomiasis. However, gastrointestinal (GI) toxicity was observed with high doses in a vervet monkey safety study. In the current study, we compared the metabolism of DB844 by hepatic and extrahepatic cytochrome P450s to determine if differences in metabolite formation underlie the observed GI toxicity. DB844 undergoes sequential O-demethylation and N-dehydroxylation in the liver to form the active compound DB820 (CPD-593-12). However, extrahepatic CYP1A1 and CYP1B1 produced two new metabolites, MX and MY. Accurate mass and collision-induced dissociation mass spectrometry analyses of the metabolites supported proposed structures of MX and MY. In addition, MY was confirmed with a synthetic standard and detection of nitric oxide release when DB844 was incubated with CYP1A1. Taken altogether, we propose that MX is formed by insertion of an oxygen into the amidine C=N to form an oxaziridine, which is followed by intramolecular rearrangement of the adjacent O-methyl group and subsequent release of nitric oxide. The resulting imine ester, MX, is further hydrolyzed to form MY. These findings may contribute to furthering the understanding of toxicities associated with benzamidoxime- and benzmethamidoxime-containing molecules

Targeted LC–MS derivatization for aldehydes and carboxylic acids with a new derivatization agent 4-APEBA

Based on the template of a recently introduced derivatization reagent for aldehydes, 4-(2-(trimethylammonio)ethoxy)benzeneaminium dibromide (4-APC), a new derivatization agent was designed with additional features for the analysis and screening of biomarkers of lipid peroxidation. The new derivatization reagent, 4-(2-((4-bromophenethyl)dimethylammonio)ethoxy)benzenaminium dibromide (4-APEBA) contains a bromophenethyl group to incorporate an isotopic signature to the derivatives and to add additional fragmentation identifiers, collectively enhancing the abilities for detection and screening of unknown aldehydes. Derivatization can be achieved under mild conditions (pH 5.7, 10 °C). By changing the secondary reagent (1-ethyl-3-(3-dimethylaminopropyl) carbodiimide instead of sodium cyanoborohydride), 4-APEBA is also applicable to the selective derivatization of carboxylic acids. Synthesis of the new label, exploration of the derivatization conditions, characterization of the fragmentation of the aldehyde and carboxylic acid derivatives in MS/MS, and preliminary applications of the labeling strategy for the analysis of aldehydes in urine and plasma are described

Cashew nut allergy: clinical relevance and allergen characterisation

Cashew plant (Anacardium occidentale L.) is the most relevant species of the Anacardium genus. It presents high economic value since it is widely used in human nutrition and in several industrial applications. Cashew nut is a well-appreciated food (belongs to the tree nut group), being widely consumed as snacks and in processed foods by the majority of world's population. However, cashew nut is also classified as a potent allergenic food known to be responsible for triggering severe and systemic immune reactions (e.g. anaphylaxis) in sensitised/allergic individuals that often demand epinephrine treatment and hospitalisation. So far, three groups of allergenic proteins have been identified and characterised in cashew nut: Ana o 1 and Ana o 2 (cupin superfamily) and Ana o 3 (prolamin superfamily), which are all classified as major allergens. The prevalence of cashew nut allergy seems to be rising in industrialised countries with the increasing consumption of this nut. There is still no cure for cashew nut allergy, as well as for other food allergies; thus, the allergic patients are advised to eliminate it from their diets. Accordingly, when carefully choosing processed foods that are commercially available, the allergic consumers have to rely on proper food labelling. In this sense, the control of labelling compliance is much needed, which has prompted the development of proficient analytical methods for allergen analysis. In the recent years, significant research advances in cashew nut allergy have been accomplished, which are highlighted and discussed in this review.This work was supported by FCT/MEC through national funds and co-financed by FEDER, under the Partnership Agreement PT2020 with grant no. UID/QUI/50006/2013–POCI/01/ 0145/FEDER/007265. Joana Costa is grateful to FCT post-doctoral grant (SFRH/BPD/102404/2014) financed by POPH-QREN (subsidised by FSE and MCTES).info:eu-repo/semantics/publishedVersio