Fungal chitin-glucan derivatives exert protective or damaging activity on plasmid DNA.

Water-soluble derivatives of the chitin-glucan (Ch-G) complex isolated from the fungal mycelium of the industrial strain of Aspergillus niger have been previously shown to possess potent antimutagenic protective activity in vivo. Their direct action on DNA has not been yet evaluated. Using carboxymethylation, sulfoethylation and subsequent ultrasonic treatment, lower molecular weight water-soluble derivatives were obtained from the crude fungal Ch-G. The biological effects of the prepared compounds were evaluated in direct interaction on plasmid DNA in vitro. Monitoring of electrophoretic mobility of different conformers of plasmid DNA implied that carboxymethyl chitin-glucan (CM-Ch-G) induced single- and double-strand breaks into supercoiled DNA in a concentration-dependent manner. On the other hand, sulfoethyl chitin-glucan (SE-Ch-G) alone did not induce any DNA breaks in plasmid DNA. However, process of DNA damaging induced by free-radical oxidation initiated with Fe(2+) was inhibited, while the process of DNA breakage induced by H(2)O(2) was increased in the presence of SE-Ch-G.