Chiroptical characterization of homopolymeric block fractions in alginates.
Homopolymannuronic and homopolyguluronic fractions were obtained by partial hydrolysis of the alkaline extracts from the brown seaweeds Ascoseira mirabilis, Desmarestia menziessi, Desmarestia ligulata and Durvillaea sp. collected in southern Chile. Full characterization of the fractions was achieved by FT-IR and NMR spectroscopy. Total hydrolysis with 90% formic acid of the homopolymeric fractions allowed the preparation of mannuronic and guluronic acids. Both monomers and homopolymeric fractions as neutral salts were studied by CD and ORD. Chiroptical spectra were similar in shape and sign to those previously published in the literature, and permitted to assign D configuration to mannuronic acid and L configuration to guluronic acid in alginic acids. Specific optical rotation values at the sodium D light for the homopolymannuronic (∼-100°) and homopolyguluronic (∼-110°) acid fractions were obtained. These high negative values are proposed for the assignment of the absolute configuration of monomers in homopolymeric fractions.
Departamento de Ciencias del Ambiente, Facultad de Química y Biología, Universidad de Santiago de Chile, Av. Libertador B. O'Higgins 3363, Santiago, Chile.
Fabián
F
Martínez-Gómez
Laboratorio de Macroalgas Antárticas y Subantárticas, Universidad de Magallanes, Av. Bulnes 1465, Punta Arenas, and Instituto de Ecología y Biodiversidad, Chile.
Andrés
A
Mansilla
Departamento de Ciencias del Ambiente, Facultad de Química y Biología, Universidad de Santiago de Chile, Av. Libertador B. O'Higgins 3363, Santiago, Chile. Electronic address: betty.matsuhiro@usach.cl.
Betty
B
Matsuhiro
Departamento de Química Orgánica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellón 2, Ciudad Universitaria, Buenos Aires, Argentina.
María C
MC
Matulewicz
Laboratorio de Química de Productos Naturales, Departamento de Botánica, Facultad de Ciencias Naturales y Oceanografía, Universidad de Concepción, Víctor Lamas 1290, Concepción, Chile.
Marcos A
MA
Troncoso-Valenzuela
D000464:Alginates / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D000459:Phaeophyceae / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared
D000464:Alginates; D011108:Polymers
Alginate; Circular dichroism; Homopolyguluronic acid; Homopolymannuronic acid; Optical rotatory dispersion; Specific optical rotation