tailieunhanh - Báo cáo khoa học: "spectroscopie de résonance paramagnétique électronique de la photodégradation des lignines extraites du bois de pin radiata (Pinus radiata D. Don)."

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài: spectroscopie de résonance paramagnétique électronique de la photodégradation des lignines extraites du bois de pin radiata (Pinus radiata D. Don). | 563 Ann. For. Sci. 56 1999 563-578 Inra Elsevier Paris Article original Etude par spectroscopic de resonance paramagnétique électronique de la photodegradation des lignines extraites du bois de pin radiata Pinus radỉata D. Don Cyril Kamouna André Merlina Xavier Deglisea Silvio H. Urizarb Anna Maria Fernandez0 Laboratoire d etude et de recherche sur le matériau bois équipe photochimie appliquée et physicochimie des polymeres université Henri Poincare Nancy 1 Enstib BP 239 54506 Vandoeuvre les Nancy cedex France bUniversidad del Bio-Bio Casilla 5-C Concepcion Chili Regu le 17 aoũt 1998 accepté le 2 fevrier 1999 Abstract - ESR study of photodegradation of lignins extracted and isolated from Pinus radiata wood. Cellulose in lignocellulosic materials is protected from photochemical degradation by the lignin which can play a three-fold role to filter near uv radiation by absorbing photons to deactivate the excited state of cellulose and by acting as an antioxidant by forming stable phenoxy radicals by radical transfer reactions. In the work presented we have studied by electron paramagnetic resonance EPR the photodegradation of lignins extracted and isolated from Pimts radiata wood. The kinetics of the intermediate radical species concentrations have been followed during irradiation of solid specimens as well as for lignins in solution both for the raw and for modified extracts after stopping light irradiation and stocking the samples in the dark in order to quantify the stability of the formed radicals. Attribution of EPR signals to phenoxy radicals formed by abstraction of an hydrogen atom from the phenolic chromophore groups of lignin has been confirmed by the study of radical transfer reactions from the DPPH radical to the lignins. The lignin ability to form resonance stabilized phenoxyl radicals confers on these materials antioxidant properties which allow the value-added use of this by-product of the pulp and paper industry. 1999 Editions scientifiques et medicales

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