5.7 mg of whole food vitamin C equivalent to 1,500 mg of vitamin C alone
A group of researchers with the Department of Food Sciences at Cornell University designed a study to assess the collective antioxidant activity of whole apple extracts. Using a total oxyradical scavenging capacity (TOSC) assay they measured the antioxidant activity of 100 grams of whole apple extracts with skin. The researchers asserted they assayed apple extracts including skin deliberately; apple skins have higher concentrations of phytochemicals – such as phenolic compounds - than does apple flesh. Moreover, antioxidants such as quercetin glycosides are only found in the skins.
Through this study, it was discovered that the antioxidant activity of 100 grams of apples is equivalent to 1,500 mg of vitamin C alone, despite the fact that the average concentration of vitamin C per 100 grams of apple extract was only 5.7 mg, or 0.057mg vitamin C per 1g of whole apples. Though the TOSC measurement for the apple with skin extract showed a statistically significant capacity to inhibit tumorcell proliferation at 83.3, the vitamin C portion of the whole apple extract showed a capacity of 0.32. This discovery led Eberhardt et al to speculate that "almost all of the antioxidant activity in apples must be due to phytochemicals."
Further evidence supporting the antioxidant activity of phytochemicals in apples - other than ascorbic acid - was revealed in two assessments of the effects of whole apple extracts on the proliferation of cancer-cell lines. Following treatment of a colon-cancer cell line, Eberhardt et al noted that cell proliferation was inhibited more significantly by apple extracts with skins, than without. This was verified again with a liver-tumor cell line, called HepG2. Again, the apple extracts with skins inhibited proliferation of these cells more significantly than apple extracts without skins. Researchers in this study speculate that the in vitro inhibition of cancer cell proliferation is a consequence of the apple’s combination of phenolic acids, flavonoids and other phytochemicals.
Study:Eberhardt M., Lee C., Liu R., Nature, vol 405, 903-904 (2000)