Physical Properties of Larch Arabinogalactan in Binary Water-Methanol Solvent Mixtures

Hergli E and Aschi A

Published on: 2024-07-22

Abstract

Herein, the investigation of the structure and the physicochemical properties of larch arabinogalactan (AG), extracted from larch tree, in water-methanol solutions were studied using different measurement techniques such as dynamic light scattering (DLS)), turbidity (optical density, OD), fluorescence, and electrical conductivity (s). The results obtained from the DLS showed that the hydrodynamic radius R_H of AG shows two concentration regimes depending on the percentage of methanol added, proving the existence of a critical concentration (65%) separating the different regimes, and the polysaccharide becomes more and more hydrophobic. The effect of sodium chloride salt (NaCl) for a concentration of 0.1 M showed that the R_H decreased, which explains the relative influence of NaCl on the conformational, three-dimensional stability of arabinogalactan. Additionally, the average absorbance turbidity (OD) profile as a function of pH for solutions of arabinogalactan and different percentages of methanol was studied showing that as the pH increased, the turbidity of the particles also increased due to a greater propensity to aggregate near its optimal pH, pH_opt ~ 7 and when the methanol concentration increases the turbidity gradually decreases indicating the change in the amphiphilic nature. Fluorescence and electrical conductivity results of the polysaccharide in binary mixture solutions were also reported concluding that arabinogalactan is a bad electrical conductor for very high alcohol concentrations.