Constituents and their antioxidative effects in eucalyptus leaf extract used as a natural food additive

The components of a natural food additive, "eucalyptus leaf extract", were isolated and identified in order to determine their structures and contents. The structures of eight major compounds, namely gallic and ellagic acids, eucalyptone and macrocarpals A-E, isolated from them were elucidated by spectroscopic methods. The antioxidative activities of these isolated compounds were estimated by several assays, and it appears that the antioxidant activity is mostly due to the gallic and ellagic acids. On the other hand, in the determined eucalyptus product, the content of 1,8-cineole, a major component of the eucalyptus oil, was lower than the isolated compounds, and its activity as an antioxidant was negligible.