Solution properties of antitumor sulfated derivative of alpha-(1->3)-D-glucan from Ganoderma lucidum

Four fractions of a water-insoluble α-(1→3)-D-glucan GL extracted from fruiting bodies of Ganoderma lucidum were dissolved in 0.25 M LiCl/DMSO, and then reacted with sulfur trioxide-pyridine complex at 80°C to synthesize a series of water-soluble sulfated derivatives S-GL. The degree of substitution of DS was measured by using IR infrared spectra, elemental analysis, and 13 C NMR to be 1.2-1.6 in the non-selective sulfation. Weight-average molecular weight M w and intrinsic viscosity [η] of the sulfated derivatives S-GL were measured by multi-angle laser light scattering and viscometry. The M w value (2.4×10 4 ) of sulfated glucan S-GL-1 was much lower than that (44.5×10 4 ) of original α-(1→3)-D-glucan GL-1. The Mark-Houwink equation and average value of characteristic ratio C ∞ for the S-GL in 0.2 M NaCl aqueous solution at 25°C were found to be: [η]=1.32×10 -3 M w 1.06 (cm 3 g -1 ) and 16, respectively, in the M w range from 1.1×10 4 to 2.4×10 4 . It indicated that the sulfated derivatives of the α-(1→3)-D-glucan in the aqueous solution behave as an expanded chain, owing to intramolecular hydrogen bonding or interaction between charge groups. Interestingly, two sulfated derivatives synthesized from the α-(1→3)-D-glucan and curdlan, a β-(1→3)-D-glucan, all had significant higher antitumor activity against Ehrlich ascites carcinoma (EAC) than the originals. The effect of expanded chains of the sulfated glucan in the aqueous solution on the improvement of the antitumor activity could not be negligible.