The components of Artemisia and Labiatae species were isolated and their ch
emical structures were determined. These compounds were found to have tanni
c activity for the first time. The activity of the compounds comes from the
caffeic acid moiety in their molecules, not from structural features of us
ual tannins (hydrolyzable and condensed tannins). These also showed several
other biological activities. Furthermore, the research on dimerization of
caffeic acid derivatives was performed.