Flavonoid
Flavonoids are a class of compounds grouped together because of their structural similarities. Flavonoids can be found in a wide variety of sources, including eucalyptus and boneset. Some examples of flavonoids are eupatorium, quercitin and hyperoside.
Flavonoids have a wide spectrum of biological activities ranging from elimination of influenza type A viral infection in chick embryos (quercitin and hyperoside) to a cytotoxic property.
References
Leung, Albert Y. 1980. Encyclopedia of Common Natural Ingredient used in Food, Drugs and Cosmetics. John Wiley and Sons, N Y. 409 pp.