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Reprinted on a not-for-profit basis
from
"Antioxidant and
Antiproliferative Activities of Selected New York Apple Cultivators,"
by Rui Jai Liu1, Marian
V. Eberhardt1, and Chang Yong Lee2
Diets rich in fruits and vegetables have been associated with lower incidences in cancer and lower mortality from coronary heart disease. Antioxidants in fruits and vegetables are thought to reduce cancer rates by counteracting the prooxidant load of the body. In addition to the presence of vitamins C and E, fruits and vegetables are a rich source of other antioxidants such as phenolic acids and flavonoids. We measured the total antioxidant activity of several apples varieties by Total Oxyradical Scavenging Capacity (TOSC) expressed as mmol vitamin C equivalents per gram.
We found that all varieties of apples that we tested exhibited great antioxidant activity. Apples with the skin had higher antioxidant activity than apples without skin. Apple skins are known to contain higher amounts of phenolic compounds than the flesh. Others have reported that the amount of phenolics in the skin of apples is several times higher than that of the flesh and that the quercetin glycosides (the most predominate flavonoid in apples) are only found in the skin. Although apples have a relatively low vitamin C content (which is one of the better known antioxidants ), they do contain relatively high amounts of other antioxidants. The vitamin C in apples accounts for only 0.4% of total antioxidant activity. Therefore, the majority of antioxidant activity of apple is not from Vitamin C, but from other phytochemicals in apples. The combination of different phytochemicals in apples may function additively or synergistically to be responsible for this potent antioxidant activity.
Apple extracts from selected apple varieties were added to human liver cancer HepG2 cells to determine if the extracts could inhibit tumor cell proliferation. There was a large variation in the effects of the different apple varieties on the inhibition of cell proliferation, but all apple varieties inhibited liver cancer cell proliferation. Apples without skin were less potent in inhibiting HepG2 cell proliferation whereas apples with skins exerted greater inhibitions of cell proliferation. Our results show that the combination of phytochemicals in apples is critical to its potent antioxidant activity and antiproliferative activity. Apple with the skin displayed higher antioxidant and antiproliferative activities than apple without skin. The total phenolic and flavonoid content was positively related to antioxidant activity and inhibition of cell proliferation. Additionally, the minimal contribution of vitamin C to the antioxidant activity of apples further supports the proposal that other phytochemicals, such as phenolic acids and flavonoids, significantly contribute to the in vitro antioxidant activity of apples.
This data provides direct supportive evidence for the Five-a-Day program, and suggests that apples are a good way for consumers to obtain their antioxidants for health improvement and disease prevention.
1 Department of Food
Science, Cornell University, Ithaca, NY
2 Department of Food Science &
Technology, Cornell University, Geneva, NY