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Galactomannans with novel structures from the lichen Roccella decipiens Darb
Elaine R Carbonero1, Lucimara M C Cordeiro, Caroline G Mellinger
1Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Paraná, UFPR, CP 19.046, CEP 81.531-990 Curitiba, PR, Brazil.
Carbohydrate Research
|June 7, 2005
Summary
Researchers isolated novel galactomannan fractions from Roccella decipiens lichen. These unique polysaccharides, FP and RFS, exhibit distinct sugar compositions and complex branching structures previously unreported in scientific literature.
Area of Science:
- Carbohydrate Chemistry
- Natural Product Chemistry
- Lichenology
Background:
- Lichens are a symbiotic association of fungi and algae, known to produce unique secondary metabolites.
- Galactomannans are complex polysaccharides found in various plant and fungal sources, with diverse structural features and biological activities.
- The chemical composition and structural elucidation of polysaccharides from less-studied organisms like Roccella decipiens remain largely unexplored.
Purpose of the Study:
- To isolate and characterize homogeneous galactomannan fractions from the lichen Roccella decipiens.
- To determine the detailed chemical structure, including sugar composition and linkage patterns, of the isolated polysaccharides.
- To report novel polysaccharide structures not previously described in scientific literature.
Main Methods:
- Isolation of homogeneous galactomannan fractions (FP and RFS) from Roccella decipiens.
- Determination of molar ratios of constituent monosaccharides (Mannose, Galactose, Glucose) using chromatographic techniques.
- Detailed structural analysis involving methylation analysis and NMR spectroscopy to elucidate glycosidic linkages and substitution patterns.
Main Results:
- Two distinct galactomannan fractions, FP (Man:Gal 81:19) and RFS (Man:Gal:Glc 43:56:1), were successfully isolated.
- FP features an alpha-D-Manp-(1→4)-linked backbone with O-2 substituted side chains of alpha-Manp, terminated by beta-D-Galf.
- RFS shares a similar alpha-D-Manp core but possesses side chains with beta-D-Galf units exhibiting various substitutions (nonreducing end, 5-O-, 6-O-, 5,6-di-O-).
Conclusions:
- Roccella decipiens yields structurally unique galactomannans with complex branching patterns.
- The elucidated structures of FP and RFS represent novel polysaccharide architectures.
- These findings contribute to the understanding of lichen secondary metabolism and carbohydrate chemistry.