We recently reported that phytochemical extracts from fruit
have strong antioxidant and antiproliferative effects and proposed
that the combination of phytochemicals in fruit and vegetables is
critical to powerful antioxidant and anticancer activity (31–33).
For example, the total antioxidant activity of phytochemicals in
1 g of apples with skin is equivalent to 83.3 mol vitamin C
equivalents—that is, the antioxidant value of 100 g apples is
equivalent to 1500 mg of vitamin C. This is much higher than the
total antioxidant activity of 0.057 mg of vitamin C (the amount of
vitamin C in 1 g of apples with skin). In other words, vitamin C
in apples contributed only < 0.4% of total antioxidant activity (31).
Thus, most of the antioxidant activity comes from phytochemicals,
not vitamin C. The natural combination of phytochemicals
in fruit and vegetables is responsible for their potent antioxidant
activity. Apple extracts also contain bioactive compounds that
inhibit tumor cell growth in vitro. Phytochemicals in 50 mg apple
with skin per milliliter (on a wet basis) inhibit tumor cell proliferation
by 42%. Phytochemicals in 50 mg apple without skin per
milliliter inhibit tumor cell proliferation by 23%. The apple
extracts with skin significantly reduced the tumor cell proliferation
when compared with the apple extracts without skin.