However, every living organism has antioxidant mechanisms
to counteract oxidative stress (1). Apart from the
endogenous antioxidant mechanisms, the supplementation of
antioxidants through diet may be used to reduce the detrimental
effects of oxidative stress on human health as suggested
by our previous studies (12,13). Some of the most well known
food sources of antioxidants are grapes and wine (14). Our
research group has conducted several studies on the antioxidant
properties of grapes which are attributed mainly to their
polyphenolic content (15-21). We have also conducted a series
of studies on the antioxidant activity of extracts from grape
stems, a by-product of the winemaking process which has
been little investigated (15,22-25). For example, in one of our
previous studies, we demonstrated that grape stem extracts are
rich in bioactive polyphenols (e.g., flavonoids, stilbenes and
phenolic acids) (22) and exhibit strong free radical scavenging
activity in vitro