Solution properties of an α-(1→3)- d-glucan from Lentinus edodes and its sulfated derivatives

Abstract

A water-insoluble α-(1→3)- d-glucan ( A ) from Lentinus edodes was fractionated into 13 fractions in dimethyl sulfoxide containing 0.25 M lithium chloride (0.25 M LiCl–Me 2SO). Five fractions were treated with sulfur trioxide–pyridine complex at 25 °C to synthesize water-soluble sulfated derivatives (S- A). The weight-average molecular weights, M w, and intrinsic viscosities [ η], of the samples A and S- A were determined by multi-angler laser light scattering (MALLS), and viscosity. The M w dependence of [ η] and of the radius of gyration 〈 S 2〉 z 1/2, was found to be represented approximately by [ η] =4.9×10 −2 M w 0.67 (cm 3 g −1), and 〈 S 2〉 z 1/2 =4.8×10 −2 M w 0.54 (nm) for the α-glucan in 0.25 M LiCl–Me 2SO in the M w range from 7.24×10 4 to 4.21×10 5, and by [ η]=6.8 ×10 −4 M w 1.06 (cm 3 g −1), and 〈 S 2〉 z 1/2 =9.4×10 −4 M w 0.92 (nm) for the sulfated α-glucan in aqueous 0.5 M NaCl in the M w range from 5.92×10 4 to 1.42×10 5 at 25 °C. The results indicate that the α-(1→3)- d-glucan exists as a flexible chain in 0.25 M LiCl–Me 2SO, and its sulfated derivative in 0.5 M NaCl aqueous has stiffer chains than the original. 13C NMR indicated that intramolecular hydrogen bonding occurred in the sulfated α-glucan, causing the observed chain stiffness.