Physiochemical properties and antitumor activities of carboxymethylated derivatives of glucan from Sclerotinia sclerotiorum.

Abstract

A highly branced antitumor (1→3)-β-D-glucan, SSG, obtained from the culture filtrate of Sclerotinia sclerotiorum IFO 9395, is hardly soluble in water. To increase the solubility of SSG, carboxymethylated derivatives were prepared by reaction with monochloroacetic acid, and the antitumor activity and physicochemical properties of the products were comnared. Carboxymethylated derivatives of SSG (CM-SSG) having DS 0.04-0.49 (DS : degree of substitution with carboxymethyl groups per anhydro glucose unit) and CM-culdlan having DS 0.04-0.38 were obtained. As assessed by viscosity, optical rotation and carbon-13 nuclear magnetic resonance (NMR) measurements, CM-SSG and CM-curdlan having DS below ca. 0.1 and ca. 0.2, respectively, formed a gel in neutral aqueous media, but derivatives having higher DS values did not. CM-SSG having DS 0-0.14 showed potent antitumor activity, but higher DS derivatives did not show the activity. On the other hand, CM-curdlan having DS 0.08-0.38 showed antitumor activity. It is suggested that 1) the DS values corresponding to the gel-to-sol transition and the antitumor activity were affected by the existence of side chains and 2) the critical DS values for antitumor activity were higher than those for gel formation.