The chemical structure of an antitumor polysaccharide in mycelia of Cochliobolus miyabeanus.

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Abstract
The chemical structure and antitumor activities of a polysaccharide from mycelia of Cochliobolus miyabeanus (Ascomycetes) were examined. The polysaccharide extracted with 4 N acetic acid was purified by Sepharose CL-4B and diethylaminoethyl (DEAE)-Sepharose column chromatography; 0.3 g of this antitumor glucan (As-I) was obtained from 100 g of dried mycelia. The purified polysaccharide (As-I) contains 99.1% sugar and 0.9% protein and its molecular weight was approximately 1.2 .times. 106. The chemical structure of As-I was determined by methylation, Smith degradation and carbon-13 nuclear magnetic resonance analyses. The results suggested that As-I has a 1,3-linked main chain with branches from the 6 position of some glucose residues. As-I (0.5 mg/kg/d) caused tumor growth inhibition in the allogeneic system of ICR mice-Sarcoma 180 tumor (50% inhibition ratio) when given by intraperitoneal injection.