<n0:ComplexDefinition xmlns:n0="http://ncicb.nci.nih.gov/xml/owl/EVS/ComplexProperties.xsd#"><n0:def-definition>A class of natural flavonoids derived from the dried leaves of the plant Camellia sinensis (tea) and related plants with potent antioxidant properties. Theaflavins are polymers derived from natural catechins which are oxidized upon drying of the plant leaf. Flavonoids such as theaflavins neutralize free-radical species and increase the activity of detoxifying phase II enzymes in the liver. In animal studies, theaflavins have been shown to exhibit antitumor effects by inducing tumor cell apoptosis, arresting cell division, inhibiting cancer cell invasion, and blocking growth factor-induced angiogenesis. Black tea contains the highest concentrations of theaflavins. (NCI04)</n0:def-definition><n0:def-source>NCI</n0:def-source></n0:ComplexDefinition>