STRUCTURE AND PROPERTIES OF AN EXTRACELLULAR POLYSACCHARIDE FROM LAETISARIA-ARVALIS - EVALUATION OF ITS ANTITUMOR-ACTIVITY

A polysaccharide isolated from the culture filtrate of Laetisaria arvalis (Basidiomycete) has been submitted to acid hydrolysis, periodate oxidation, Smith degradation, methylation analysis, and treatment with endo-(1 --> 3)-beta-D-glucanase. A 6-O-branched (1 --> 3)-beta-D-glucan with a structure similar to that of scleroglucan has been identified. In aqueous solution, this polysaccharide develops high viscosities and shows pseudoplastic behaviour. Increasing NaOH concentration reduces viscosity, which is due to a similar conformational transition to that found for scleroglucan. The antitumour activity of the glucan was tested against solid Sarcoma-180 in mice. The polysaccharide strongly inhibited tumour growth with an inhibition ratio of almost 100%.