The aim was to detect antimutagenic and DNA protective effects of a plant extract from bark of Magnolia officinalis adversing oxidative DNA damage. The ability to inhibit mutagenicity induced by tert-butyl hydroperoxide (t-BOOH) and hydrogen peroxide (H2O2) was determined with Ames test using Salmonella typhimurium His- TA102 bacterial strain. Inhibition values of 72.8 and 98.7 % were detected for t-BOOH and H2O2, respectively. The protective effect of the extract against DNA strand scission induced by hydroxyl radicals was studied with plasmid pBluescript II SK(-). The analysis of DNA strand breaks in the plasmid DNA proved a significant inhibition of DNA damage.