There is great interest in plant polyphenolic com-pounds because of their potential roles as cancer chem-opreventive agents and chronic disease protectors. Their beneﬁcial eﬀect is considered to be mainly due to their antioxidant and chelating activities. One of the major groups of polyphenolic compounds is the ﬂavonoids which occur widely in plant foods, such as fruits, vegetables, cereals and beverages (Anila & Vijayalakshmi, 2002; Bravo, 1998; Cook & Samman, 1996; Harborne, 1989; Lakenbrink, Lapczynski, Maiwald, & Engelhardt, 2000). There is an increasing interest in polyphenols due to their potentially positive eﬀect against certain dis-eases, namely mainly some forms of cancer and coro-nary heart diseases. They can act as free radical-scavengers, neutralizing dangerous reactive oxygen species and metal ion chelators. Both of these activities are responsible for antioxidant properties. Flavonoids and other plant phenolics have been reported to have a in vitro antioxidant activities, even higher than the common antioxidants, vitamin C and E (Rice-Evans, Miller, & Paganga, 1997; Scott, Butler, Halliwell, & Aruoma, 1993). The antioxidant capacity of this diverse group of compounds depends on the individual structure and number of hydroxyl groups.