STUDIES ON FUNGAL POLYSACCHARIDE .38. STRUCTURE AND ANTITUMOR-ACTIVITY OF THE LESS-BRANCHED DERIVATIVES OF AN ALKALI-SOLUBLE GLUCAN ISOLATED FROM OMPHALIA-LAPIDESCENS

The structure and antitumor activity of Smith-type degradation products (OL-2-I, OL-2-II and OL-2-III) of an alkali-soluble glucan, OL-2, isolated from a crude fungal drug ''Leiwan'' (Omphalia lapidescens) were investigated. Methylation analysis suggested that OL-2-I was a (1 --> 3)-beta-D-glucan with approximately one branch at every three main chain glucosyl units at each C-6 position; OL-2-II was a (1 --> 3)-beta-D-glucan with approximately one branch at two main chain glucosyl units at each C-6 position, and OL-2-III was a (1 --> 3)-beta-D-glucan with approximately one branch at twenty four main chain glucosyl units at each C-6 position (number of all main chain glucosyl units is on average). OL-2-I, OL-2-II and OL-2-III which were Smith-type degradation products of OL-2, showed potent antitumor activity against the solid form of sarcoma 180 in ICR mice. These results indicated that the degree of beta-linked branching at position 6 was remarkably related to the antitumor activity.