Among the bioactive metabolites produced by marine organism, phlorotannins currently attract special attention due to their highantibiotic, antifungal, and cytotoxic capacities. Phlorotannins are unique phenolic metabolites of brown algae – oligomers and polymers of phloroglucinol (1,3,5-trihydroxybenzene). Brown algae contain from 0.5 to 30% phlorotannins per dry weight. Different phlorotannin preparations are currently extensively studied from the perspective of their use in clinical pharmacy. However, these biologically active compounds are still not tested for their possible deleterious side effects, such as mutagenic activity.