Eucalyptus globulus is one of the main forest species in Galicia, representing 27% of total wood volume. Eucalyptus wood is used mainly to produce cellulose pulp and, secondly, panels and boards. In both cases, eucalyptus bark is separated as a waste product and used as fuel. Yazaki and Hillis detected ellagitannins, methyl and glycosyl derivatives of ellagic acid and free ellagic and gallic acids in methanolic extracts of the bark of various eucalyptus species. Gallotannins and cathechin were found in the tannins extracts obtained after acid hydrolysis of eucalyptus barks. Methanolic extracts of E. globulus bark were characterized by an abundance of total phenols, polymeric proanthocyanidins and ellagitannins. Increasing interest in the replacement of synthetic antioxidants has led to the research into natural sources of antioxidants, especially in plant materials.