Structural characterization of polysaccharide obtained from red seaweed Gracilaria caudata (J Agardh)

Abstract

Seaweeds are considered an important source of bioactive molecules. In this work the marine red alga Gracilaria caudata was submitted to aqueous extraction of their polysaccharides for 2 h at 100 °C. The polysaccharide fraction (PGC) presented a recovery of 32.8%. The sulfate content of PGC, calculated by S%, is 1 ± 0.2% and the degree of sulfation accounts for 0.13 ± 0.2. High-Performance Size-Exclusion Chromatography demonstrated that PGC consists of a high molecular weight polysaccharide (2.5 × 10(5)gmol(-1)). Chemical analysis of PGC was performed by microanalysis, infrared (FT-IR) and nuclear magnetic resonance (NMR, 1 and 2D) spectroscopy. The structure of PGC is mainly constituted by the alternating residues 3-linked-β-D-galactopyranose and 4-linked-3,6-α-L-anhydrogalactose; however some hydroxyl groups were substituted by methyl groups and pyruvic acid acetal. The biological precursor of 3,6-α-L-anhydrogalactose (6-sulfate-α-l-galactose) was also detected.

<b>Extraction and structural properties of <i>Acanthophora muscoides </i>(Rhodophyceae) extracellular matrix sulfated polysaccharides and their effects on coagulation

“…Furthermore, spectral data revealed signals representative of 2-O-CH 3 , 6-SO 3 -and 6-unsubstituted from 1 H-2 and 13 C-2 pairs due to a methyl-esterified site showing methylation pattern possibly attached to O-6 of D-galactose (Duarte et al, 2004;Barros et al, 2013;Quinderé et al, 2014), as was also previously suggested ( Figures 1A, B and C). It has been widely described the degree of substitution of methyl ether at C-6 varying among species (Cardozo et al, 2007;Maciel et al, 2008: Prajapati et al, 2014.…”

“…Due to the association between the intensity signals attributed to methyl hydrogens (around δ H 1.4-1.6 ppm) and the L-galactose residue (δ H 5.3 ppm), it was denoted in this study the presence of pyruvated (Pyr)-D-galactose residues in the 1 H-13 C edited-HSQC spectral value of A. muscoides galactans based on Barros et al (2013), and this structural feature was in accordance to the Acanthophora genus (Duarte et al, 2004), consistent with 1 H NMR spectral data ( Figures 1A, B and C), since pyruvic acid has not been frequently found in agarophytes (Cardozo et al, 2007). Furthermore, spectral data revealed signals representative of 2-O-CH 3 , 6-SO 3 -and 6-unsubstituted from 1 H-2 and 13 C-2 pairs due to a methyl-esterified site showing methylation pattern possibly attached to O-6 of D-galactose (Duarte et al, 2004;Barros et al, 2013;Quinderé et al, 2014), as was also previously suggested ( Figures 1A, B and C).…”

“…The lack of typical signals for galactans in the current study would reinforce the previous 1 H NMR results due to diverse unresolved peaks variable intensity presenting among the analyzed samples ( Figures 1A, B and C). The main anomeric chemical shifts values at δ H/C 4.74/101 ppm were tentatively assigned to the H-1/C-1 of β-D-galactose (β-D-Gal) (resonating at up-field regions and belonging to the 4-linked units) linked to 6-O-sulfate-α-L-galactopyranose (6-O-Sul-α-L-Gal) (δ H1/C1 5.3/102 ppm) (Duarte et al, 2004) or to 3,6-α-L-anhydrogalactose (3,6-α-L-AGal) (δ H1/C1 5.22/98.1 ppm) (Barros et al, 2013) that resonated at down-field regions and belonged to the 3-linked units. Estevez, Ciancia, and Cerezo (2008) evaluated the system of SPs from the red seaweed Gymnogongrus torulosus and observed that hot-water extractions would result in both carrageenan and agaran, but presenting the highest amount of agaran-structures.…”

“…SPs from red seaweeds have highly complex structures varying among different species (Estevez et al, 2008;Maciel et al, 2008;Fenoradosoa et al, 2009;Mourão, 2015) due to their different patterns on the sulfate position, linkage, side-chain substitutions and presence of methyl ethers or anhydro sugars (Cardozo et al, 2007;Maciel et al, 2008;Barros et al, 2013). They are homogeneous with basis on their backbone constitution, composed of alternating units of 3-linked β-galactopyranosyl (G-units) and 4-linked α-galactopyranosyl (D-units) or 3,6-anhydro-α-galactopyranpose (AnGal-units), with variable density in the sulfated group.…”

A Review of Current Research into the Biogenic Synthesis of Metal and Metal Oxide Nanoparticles via Marine Algae and Seagrasses

“…These polysaccharides mainly consist of small sugar units linked via glycosidic bonds, which have hydrophilic surface groups such as carboxyl, hydroxyl, and sulfate groups [80]. Typical polysaccharides found in seaweeds include agar, alginate, carrageenan, fucoidan, and laminarin [81]. Other biomolecules found in the cell walls include proteins and enzymes.…”