114E-27 |
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M. V. EBERHARDT1, A. S. Keck2, and E. H. Jeffery1. (1) Dept. of Food Science & Human Nutrition, Univ. of Illinois, Urbana-Champaign, 905 S. Goodwin Ave., 260 Bevier Hall, MC 182, Urbana, IL 61801, (2) Department of Food Science and Human Nutrition, University of Illinois, 1101 W. Peabody, Room 382, Urbana, IL 61801 Epidemiological studies suggest that the consumption of broccoli protects against cancer. Broccoli contains the proven anticarcinogen sulforaphane as well as a variety of antioxidants. Antioxidants, which scavenge free radicals, may aid in the prevention of cancer. Therefore, it has been suggested that estimates of antioxidant activity of fruit or vegetable extracts may indicate potential for plant foods to reduce oxidative stress and/or prevent cancer. The objective of this study was to examine the effect of broccoli extracts on i) a chemical assay of antioxidant capacity; ii) a cellular assay for oxidative stress; iii) cellular assays for quinone reductase and thioredoxin reductase. Water extracts of 22 broccoli genotypes were used to measure the antioxidant capacity, using the 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) assay. Inhibition of cellular oxidation in human liver HepG2 cells was evaluated using 2’,7’-dichlorofluorescein diacetate, which fluoresces when oxidized, after acute treatment with broccoli extracts. The effect of 24hr incubation of HepG2 cells with broccoli extracts on the induction of quinone reductase and thioredoxin reductase was also determined. The chemical assay for antioxidant activity was not correlated to a reduction in oxidative stress (R=0.310). No significant correlation was seen between antioxidant capacity and induction of thioredoxin reductase (R=0.248) or quinone reductase (R=0.192). Broccoli extracts caused a 1.8-fold increase in thioredoxin reductase and a 1.2-fold increase in quinone reductase compared to control after 24hr incubation, yet these increases did not correlate with acute inhibition of oxidative stress (R=0.310 and R=0.18, respectively). These data suggest that neither chemical nor cellular measures of oxidative stress reflect anticarcinogenic enzyme inducing capacity of broccoli extracts.
Session 114E, Nutraceuticals & Functional Foods: Bioactivity measurement and mechanism
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