Structural Features and Rheological Properties of a Sulfated Xylogalactan-Rich Fraction Isolated from Tunisian Red Seaweed <i>Jania adhaerens</i>
oleh: Faiez Hentati, Cédric Delattre, Christine Gardarin, Jacques Desbrières, Didier Le Cerf, Christophe Rihouey, Philippe Michaud, Slim Abdelkafi, Guillaume Pierre
| Format: | Article |
|---|---|
| Diterbitkan: | MDPI AG 2020-03-01 |
Deskripsi
A novel sulfated xylogalactan-rich fraction (JSP for <i>J. adhaerens</i> Sulfated Polysaccharide) was extracted from the red Tunisian seaweed <i>Jania adhaerens</i>. JSP was purified using an alcoholic precipitation process and characterized by Attenuated Total Reflectance-Fourier-transform infrared spectroscopy (ATR-FTIR), high-pressure size exclusion chromatography (HPSEC) with a multi-angle laser light scattering (MALLS), gas chromatography coupled to mass spectrometry (GC-MS) and nuclear magnetic resonance spectroscopy (NMR, 1D and 2D). JSP was then evaluated regarding its physicochemical and rheological properties. Results showed that JSP was mainly composed of an agar-like xylogalactan sharing the general characteristics of corallinans. The structure of JSP was mainly composed of agaran disaccharidic repeating units (→3)-β-<span style="font-variant: small-caps;">d</span>-Gal<i>p</i>-(1,4)-α-<span style="font-variant: small-caps;">l</span>-Gal<i>p</i>-(1→)<sub>n</sub> and (→3)-β-<span style="font-variant: small-caps;">d</span>-Gal<i>p</i>-(1,4)-3,6-α-<span style="font-variant: small-caps;">l</span>-AnGal<i>p</i>-(1→)<sub>n</sub>, mainly substituted on <i>O</i>-6 of (1,3)-β-<span style="font-variant: small-caps;">d</span>-Gal<i>p</i> residues by β-xylosyl side chains, and less with sulfate or methoxy groups. (1,4)-α-<span style="font-variant: small-caps;">l</span>-Gal<i>p</i> residues were also substituted by methoxy and/or sulfate groups in the <i>O</i>-2 and <i>O</i>-3 positions. Mass-average and number-average molecular masses (M<sub>w</sub>) and (M<sub>n</sub>), intrinsic viscosity ([<i>η</i>]) and hydrodynamic radius (R<sub>h</sub>) for JSP were, respectively, 8.0 × 10<sup>5</sup> g/mol, 1.0 × 10<sup>5</sup> g/mol, 76 mL/g and 16.8 nm, showing a flexible random coil conformation in solution. The critical overlap concentration C* of JSP was evaluated at 7.5 g/L using the Williamson model. In the semi-diluted regime, JSP solutions displayed a shear-thinning behavior with a great viscoelasticity character influenced by temperature and monovalent salts. The flow characteristics of JSP were described by the Ostwald model.