Polyphénols (propriétés de complexation et activité antioxydante)

LE TRAVAIL DE RECHERCHE PRESENTE DANS CE MEMOIRE DE THESE CONCERNE UN PIGMENT PULVINIQUE, LA NORBADIONE A, EXTRAIT DE PISOLITHUS ARHIZUS. CETTE ETUDE NOUS A PERMIS DE MIEUX COMPRENDRE D'UN POINT DE VUE MOLECULAIRE LE ROLE DE LA NORBADIONE A DANS LES PROCESSUS DE COMPLEXATION, D'ECHANGE ET D'ACCUMULATION DE RADIONUCLEIDES (137CS) OU DE METAUX LOURDS (CD(II), NI(II), PB(II)). CE SUJET A NECESSITE LA MISE EN COMMUN DE COMPETENCES PLURIDISCIPLINAIRES (MYCOLOGIE, EXTRACTION DE SUBSTANCES NATURELLES, ANALYSE DE TRACES ORGANIQUES, PHYSICO-CHIMIE EN SOLUTION) ET L'UTILISATION DES DEVELOPPEMENTS LES PLUS RECENTS DE METHODES ANALYTIQUES (SPECTROPHOTOMETRIE, RMN, SPECTROMETRIE DE MASSE, POTENTIOMETRIE, VOLTAMPEROMETRIE CYCLIQUE). NOS RESULTATS ONT ETE PUBLIES DANS CHEMICAL COMMUNICATIONS, CITES PAR NATURE ET REPRIS DANS DE NOMBREUX ARTICLES DE PRESSE (L'EXPRESS, THE GUARDIAN, ...).NOS RESULTATS ONT REVELE QUE DANS LA GAMME DE P[H] (6,0 - 6,5) QUI A ETE MESUREE DANS LES CHAMPIGNONS, LA NORBADIONE A ETAIT MAJORITAIREMENT PRESENTE SOUS UNE FORME DIENOLATE. NOUS AVONS AUSSI MONTRE QUE LA NORBADIONE A ETAIT CAPABLE D'ACCUMULER DES CATIONS MONOVALENTS (CS+, K+, TL(I)) GRACE A DES PROPRIETES ALLOSTERIQUES QUI FAVORISENT LA FORMATION DE COMPLEXES BIMETALLIQUES. AVEC LES METAUX DIVALENTS CONSIDERES DANS CETTE ETUDE (CD(II), NI(II), PB(II)) LA COMPLEXATION DE DEUX CATIONS EST DEFAVORISEE POUR DES RAISONS ELECTROSTATIQUES. LE COMPLEXE NATUREL DE LA NORBADIONE A ECHANGE SES CATIONS POTASSIUM AVEC LE CESIUM OU LE THALLIUM(I), COMME L'A MONTRE LA SPECTROMETRIE DE MASSE. ENFIN, NOUS AVONS DETERMINE POUR LA NORBADIONE A UNE ACTIVITE RADICALAIRE COMPARABLE A CELLE DES POLYPHENOLS LES PLUS ABONDANTS DANS LES FRUITS ET LES LEGUMES ET UN POUVOIR ANTIOXYDANT MODERE.THIS PHD MANUSCRIPT PRESENTS AN ORIGINAL AND HIGHLY COLLABORATIVE RESEARCH WORK ON NORBADIONE A, A FUNGAL PIGMENT WHICH WAS ISOLATED FROM PISOLITHUS ARHIZUS. THIS STUDY WAS UNDERTAKEN IN ORDER TO GAIN INSIGHT INTO COMPLEXATION, EXCHANGE AND ACCUMULATION OF RADIONUCLIDES (137CS) OR HEAVY METALS (CD(II), NI(II), PB(II)). THIS SUBJECT REQUIRED INTERDISCIPLINARY EXPERTISE (MYCOLOGY, NATURAL PRODUCTS EXTRACTION AND CHARACTERISATION, ORGANIC TRACES ANALYSIS, PHYSICOCHEMISTRY) AND WAS USING THE MOST RECENT DEVELOPMENTS OF ANALYTICAL METHODS (SPECTROPHOTOMETRY, NMR, MASS SPECTROMETRY, POTENTIOMETRY, CYCLIC VOLTAMMETRY). OUR RESULTS WERE PUBLISHED IN CHEMICAL COMMUNICATIONS, HIGHLIGHTED IN NATURE AND EMPHASISED IN DIFFERENT PRESS ARTICLES (L'EXPRESS, THE GUARDIAN, ...).OUR RESULTS REVEALED THAT IN THE P[H] RANGE (BETWEEN 6.0 AND 6.5) WHICH IS TYPICAL FOR MUSHROOMS, THE MAJOR SPECIES OF FREE NORBADIONE A IS THE DIENOLATE FORM. WE SHOWED THAT NORBADIONE A WAS ABLE TO ACCUMULATE MONOVALENT CATIONS (CS+, K+, TL(I)) DUE TO ALLOSTERIC PROPERTIES WHICH FAVORS THE FORMATION OF BIMETALLIC COMPLEXES. ON THE OTHER HAND, NORBADIONE A FORMS MONONUCLEAR COMPLEXES WITH HEAVY METALS LIKE CD(II), NI(II) AND PB(II), THE CORRESPONDING DINUCLEAR ANALOGS BEING LESS STABLE FOR ELECTROSTATIC REASONS. THE NATURAL DIPOTASSIC NORBADIONE A COMPLEX EXCHANGES ITS POTASSIUM CATIONS WITH CAESIUM OR THALLIUM(I), AS SHOWN BY ELECTROSPRAY MASS SPECTROMETRY. FINALLY, WE DETERMINED FOR NORBADIONE A AN ANTIRADICALAR POWER COMPARABLE WITH THAT OF THE MOST ABUNDANT POLYPHENOLS PRESENT IN FRUITS AND VEGETABLES AND A MODERATE ANTIOXIDANT ACTIVITY.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

Photolysis of dicamba (3,6-dichloro-2-methoxybenzoic acid) in aqueous solution and dispersed on solid supports

Dicamba (3,6-dichloro-2-methoxybenzoic acid) was exposed to UV light in aqueous solution. It was also irradiated in the solid phase without support or adsorbed on laponite (a synthetic clay) and ferric oxide