Epidemiological studies have consistently shown that regular consumption of fruits and vegetables is strongly associated with reduced risk of developing chronic diseases, such as cancer and cardiovascular disease. It is now widely believed that the actions of the antioxidant nutrients alone do not explain the observed health benefits of diets rich in fruits and vegetables, because taken alone, the individual antioxidants studied in clinical trials do not appear to have consistent preventive effects. Work performed by our group and others has shown that fruits and vegetable phytochemical extracts exhibit strong antioxidant and antiproliferative activities and that the major part of total antioxidant activity is from the combination of phytochemicals. We proposed that the additive and synergistic effects of phytochemicals in fruits and vegetables are responsible for these potent antioxidant and anticancer activities and that the benefit of a diet rich in fruits and vegetables is attributed to the complex mixture of phytochemicals present in whole foods. This explains why no single antioxidant can replace the combination of natural phytochemicals in fruits and vegetables to achieve the health benefits. The evidence suggests that antioxidants or bioactive compounds are best acquired through whole-food consumption, not from expensive dietary supplements. We believe that a recommendation that consumers eat 5 to 10 servings of a wide variety of fruits and vegetables daily is an appropriate strategy for significantly reducing the risk of chronic diseases and to meet their nutrient requirements for optimum health.

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Potential Synergy of Phytochemicals in Cancer Prevention: Mechanism of Action

Consumption of fruits and vegetables has been shown to be effective in the prevention of chronic diseases. These benefits are often attributed to the high antioxidant content of some plant foods. Apples are commonly eaten and are large contributors of phenolic compounds in European and North American diets. The peels of apples, in particular, are high in phenolics. During applesauce and canned apple manufacture, the antioxidant-rich peels of apples are discarded. To determine if a useful source of antioxidants is being wasted, the phytochemical content, antioxidant activity, and antiproliferative activity of the peels of four varieties of apples (Rome Beauty, Idared, Cortland, and Golden Delicious) commonly used in applesauce production in New York state were investigated. The values of the peels were compared to those of the flesh and flesh + peel components of the apples. Within each variety, the total phenolic and flavonoid contents were highest in the peels, followed by the flesh + peel and the flesh....

Antioxidant activity of apple peels

Consumption of fruits and vegetables has been associated with reduced risk of chronic diseases such as cardiovascular disease and cancer. Phytochemicals, especially phenolics, in fruits and vegetables are suggested to be the major bioactive compounds for the health benefits. However, the phenolic contents and their antioxidant activities in fruits and vegetables were underestimated in the literature, because bound phenolics were not included. This study was designed to investigate the profiles of total phenolics, including both soluble free and bound forms in common fruits, by applying solvent extraction, base digestion, and solid-phase extraction methods. Cranberry had the highest total phenolic content, followed by apple, red grape, strawberry, pineapple, banana, peach, lemon, orange, pear, and grapefruit. Total antioxidant activity was measured using the TOSC assay. Cranberry had the highest total antioxidant activity (177.0 +/- 4.3 micromol of vitamin C equiv/g of fruit), followed by apple, red grape, strawberry, peach, lemon, pear, banana, orange, grapefruit, and pineapple. Antiproliferation activities were also studied in vitro using HepG(2) human liver-cancer cells, and cranberry showed the highest inhibitory effect with an EC(50) of 14.5 +/- 0.5 mg/mL, followed by lemon, apple, strawberry, red grape, banana, grapefruit, and peach. A bioactivity index (BI) for dietary cancer prevention is proposed to provide a new alternative biomarker for future epidemiological studies in dietary cancer prevention and health promotion.

Antioxidant and Antiproliferative Activities of Common Fruits

A cellular antioxidant activity (CAA) assay for quantifying the antioxidant activity of phytochemicals, food extracts, and dietary supplements has been developed Dichlorofluorescin is a probe that is trapped within cells and is easily oxidized to fluorescent dichlorofluorescein (DCF) The method measures the ability of compounds to prevent the formation of DCF by 2,2′-azobis(2-amidinopropane) dihydrochloride (ABAP)-generated peroxyl radicals in human hepatocarcinoma HepG2 cells The decrease in cellular fluorescence when compared to the control cells indicates the antioxidant capacity of the compounds The antioxidant activities of selected phytochemicals and fruit extracts were evaluated using the CAA assay, and the results were expressed in micromoles of quercetin equivalents per 100 µmol of phytochemical or micromoles of quercetin equivalents per 100 g of fresh fruit Quercetin had the highest CAA value, followed by kaempferol, epigallocatechin gallate (EGCG), myricetin, and luteolin among the pure co

Cellular Antioxidant Activity (CAA) Assay for Assessing Antioxidants, Foods, and Dietary Supplements

Epidemiological studies have shown that consumption of fruits and vegetables is associated with reduced risk of chronic diseases. Increased consumption of fruits and vegetables containing high levels of phytochemicals has been recommended to prevent chronic diseases related to oxidative stress in the human body. In this study, 10 common vegetables were selected on the basis of consumption per capita data in the United States. A more complete profile of phenolic distributions, including both free and bound phenolics in these vegetables, is reported here using new and modified methods. Broccoli possessed the highest total phenolic content, followed by spinach, yellow onion, red pepper, carrot, cabbage, potato, lettuce, celery, and cucumber. Red pepper had the highest total antioxidant activity, followed by broccoli, carrot, spinach, cabbage, yellow onion, celery, potato, lettuce, and cucumber. The phenolics antioxidant index (PAI) was proposed to evaluate the quality/quantity of phenolic contents in these vegetables and was calculated from the corrected total antioxidant activities by eliminating vitamin C contributions. Antiproliferative activities were also studied in vitro using HepG(2) human liver cancer cells. Spinach showed the highest inhibitory effect, followed by cabbage, red pepper, onion, and broccoli. On the basis of these results, the bioactivity index (BI) for dietary cancer prevention is proposed to provide a simple reference for consumers to choose vegetables in accordance with their beneficial activities. The BI could be a new alternative biomarker for future epidemiological studies in dietary cancer prevention and health promotion.

Antioxidant and antiproliferative activities of common vegetables.

Processed fruits and vegetables have been long considered to have lower nutritional value than their fresh commodities due to the loss of vitamin C during processing This research group found vitamin C in apples contributed < 04% of total antioxidant activity, indicating most of the activity comes from the natural combination of phytochemicals This suggests that processed fruits and vegetables may retain their antioxidant activity despite the loss of vitamin C Here it is shown that thermal processing elevated total antioxidant activity and bioaccessible lycopene content in tomatoes and produced no significant changes in the total phenolics and total flavonoids content, although loss of vitamin C was observed The raw tomato had 076 +/- 003 micromol of vitamin C/g of tomato After 2, 15, and 30 min of heating at 88 degrees C, the vitamin C content significantly dropped to 068 +/- 002, 064 +/- 001, and 054 +/- 002 micromol of vitamin C/g of tomato, respectively (p < 001) The raw tomato had 201 +/- 004 mg of trans-lycopene/g of tomato After 2, 15, and 30 min of heating at 88 degrees C, the trans-lycopene content had increased to 311+/- 004, 545 +/- 002, and 532 +/- 005 mg of trans-lycopene/g of tomato (p < 001) The antioxidant activity of raw tomatoes was 413 +/- 036 micromol of vitamin C equiv/g of tomato With heat treatment at 88 degrees C for 2, 15, and 30 min, the total antioxidant activity significantly increased to 529 +/- 026, 553 +/- 024, and 670 +/- 025 micromol of vitamin C equiv/g of tomato, respectively (p < 001) There were no significant changes in either total phenolics or total flavonoids These findings indicate thermal processing enhanced the nutritional value of tomatoes by increasing the bioaccessible lycopene content and total antioxidant activity and are against the notion that processed fruits and vegetables have lower nutritional value than fresh produce This information may have a significant impact on consumers' food selection by increasing their consumption of fruits and vegetables to reduce the risks of chronic diseases

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Thermal Processing Enhances the Nutritional Value of Tomatoes by Increasing Total Antioxidant Activity

Processed fruits and vegetables have been long considered to have lower nutritional value than the fresh produce due to the loss of vitamin C during processing. Vitamin C in apples has been found to contribute <0.4% of total antioxidant activity, indicating most of the activity comes from the natural combination of phytochemicals. This suggests that processed fruits and vegetables may retain their antioxidant activity despite the loss of vitamin C. Here it is shown that thermal processing at 115 degrees C for 25 min significantly elevated the total antioxidant activity of sweet corn by 44% and increased phytochemical content such as ferulic acid by 550% and total phenolics by 54%, although 25% vitamin C loss was observed. Processed sweet corn has increased antioxidant activity equivalent to 210 mg of vitamin C/100 g of corn compared to the remaining 3.2 mg of vitamin C in the sample that contributed only 1.5% of its total antioxidant activity. These findings do not support the notion that processed fruits and vegetables have lower nutritional value than fresh produce. This information may have a significant impact on consumers' food selection by increasing their consumption of fruits and vegetables to reduce the risk of chronic diseases.

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Veronica Dewanto

Papers

Thermal Processing Enhances the Nutritional Value of Tomatoes by Increasing Total Antioxidant Activity

Processed Sweet Corn Has Higher Antioxidant Activity