The antioxidative activity and antimutagenic effects of the water-soluble beta-(1-3)-D-glucan derivatives from biotechnologically important species, in particular carboxymethyl-glucan (CM-G) and sulfoethyl-glucan (SE-G) both from the baker's yeast Saccharomyces cerevisiae, and carboxymethyl-chitin-glucan (CM-CG) from filamentous fungus Aspergillus niger, were evaluated. The luminol-dependent photochemical method using trolox as a standard showed that CM-CG, SE-G and CM-G possessed high antioxidative properties. CM-CG exhibited the highest antioxidative activity (2.15 +/- 0.14 nmol exhibits the same activity as 1 nmol of trolox), followed by SE-G (2.99 +/- 0.15 nmol) and CM-G (4.59 +/- 0.14 nmol). These glucans were experimentally confirmed to exhibit different, statistically significant activity in reducing the damage of chloroplast DNA of the flagellate Euglena gracilis induced by ofloxacin and acridine orange. Our findings suggest that the antimutagenic effect of CM-CG, SE-G and CM-G against ofloxacin is based on their antioxidative capability to scavenge reactive oxygen species (p < 0.001). As far as acridine orange is concerned, the reduction of the chloroplast DNA lesion could be a result of the absorptive capacity of the glucans (p < 0.001). We found out that the water-soluble beta-(1-3)-D-glucan derivatives possess very high antioxidative activity as well as expressive antimutagenic effects, exerted through different mode of action.