RESUMO
The galactan system biosynthesized by the red seaweed Gymnogongrus tenuis (Phyllophoraceae) is constituted by major amounts of κ/ι-carrageenans, with predominance of ι-structures, which were isolated by extraction with hot water in high yield (â¼ 45%). A small amount of non-cyclized carrageenans mostly of the ν-type was also obtained. Besides, 12% of these galactans are agaran structures, which were present in major quantities in the room temperature water extracts, but they were also found in the hot water extract. They are constituted by 3-linked ß-D-galactose units partially substituted on C-6 with sulfate or single stubs of ß-D-xylose and 4-linked residues that comprise α-L-galactose units partially sulfated or methoxylated on C-3 or sulfated on C-3 and C-6 and 3,6-anhydro-α-L-galactose. Related structural patterns were previously found for agarans synthesized by other carrageenophytes. Results presented here show that these agarans are low molecular weight molecules independent of the carrageenan structures, with strong interactions between them.
Assuntos
Carragenina/química , Galactanos/química , Rodófitas/química , Alga Marinha/química , Carragenina/isolamento & purificação , Galactanos/isolamento & purificação , Temperatura Alta , Água/químicaRESUMO
The structures of two sulfated xylomannans extracted from the red alga Nemalion helminthoides were determined. These two fractions plus a sulfated mannan, isolated from the same alga and whose structure was previously reported, were subjected to chemical modification. The mannan was oversulfated with SO(3)-pyridine in dimethyl sulfoxide at 60 °C during two and three hours and the xylomannans were subjected to Smith degradation in order to eliminate xylose side-chains. Structural analysis of all derivatives was carried out by methylation analysis and (13)C NMR spectroscopy. Antiviral activity against herpes simplex virus type 1 and 2, and dengue virus type 2 of native and modified mannans and xylomannans was estimated. Anticoagulant effect of the active fractions was also determined.
Assuntos
Anticoagulantes/isolamento & purificação , Anticoagulantes/farmacologia , Antivirais/isolamento & purificação , Antivirais/farmacologia , Mananas/isolamento & purificação , Mananas/farmacologia , Rodófitas/química , Ésteres do Ácido Sulfúrico/isolamento & purificação , Ésteres do Ácido Sulfúrico/farmacologia , Anticoagulantes/química , Antivirais/química , Vírus da Dengue/efeitos dos fármacos , Herpesvirus Humano 1/efeitos dos fármacos , Herpesvirus Humano 2/efeitos dos fármacos , Mananas/química , Estrutura Molecular , Ressonância Magnética Nuclear Biomolecular , Ésteres do Ácido Sulfúrico/química , Xilose/química , Xilose/farmacologiaRESUMO
Nemalion helminthoides, collected in the Argentine South Atlantic coast, was extracted with hot water and the crude product fractionated using cetrimide. The complexed material was subjected to fractional solubilization in solutions of increasing sodium chloride concentration and seven fractions were separated and analyzed. Structural analysis of the main fractions, those soluble in 3.0 and 4.0 M NaCl (yields 21.0% and 13.8%, respectively) and those insoluble in 4.0 M NaCl (yield 20.0%), indicated that this seaweed biosynthesizes (1-->3)-linked alpha-D-mannans that are sulfated at positions 4 and 6. Three mannan fractions comprising considerable amounts of xylose were also isolated in very low total yield (2.0%). The fractions that were soluble in 3.0 and 4.0 M NaCl showed low antiherpetic activity whereas this activity was considerable for the fraction solubilized in 2.0 M NaCl (yield 0.5%) which contained single stubs of beta-D-xylose. A xylan, soluble in cetrimide solution, containing (1-->3, 1-->4)-linked beta-D-xylose residues, was also isolated in minor amount.