Determination of antioxidant capacity of selenium-enriched wheat seeds
Öztolan, Nihal (2009) Determination of antioxidant capacity of selenium-enriched wheat seeds. [Thesis]
Selenium-containing proteins are essential in mammalian systems and have critical biochemical functions. Reduction in oxidative stress, inhibition of uncontrolled cell proliferation and preventing different type of cancers are among the significant functions of selenium (Se) in mammalian systems. Due to the fact that animals cannot synthesize their own seleno-proteins, adequate amount of Se must be taken by daily diets. Consuming Se-rich foods is, thus, a crucial issue for human nutrition and health. Among the foods consumed commonly, wheat represents one of the most important staple foods contributing to the daily Se intake of human-beings. Enrichment of wheat with Se is, therefore, an important research area and public health issue. In literature, there is, however, limited information about the antioxidative effects of wheat enriched with Se by applying Se-fertilizers. This study basically analyzed antioxidant capacity of Se-enriched wheat seeds by using various colorimetric assays and human cell culture methods. The seeds used in this work were obtained from a Se-fertilizer project conducted in different locations in Central Anatolia. The Se concentration of seed samples used showed a range between 28 ppb and 7168 ppb. In order to test the antioxidant capacity of seeds differing in Se concentrations, hot water, cellulose and methanol/ acetone/ water extracts of seeds were used. The assays applied for measurement of antioxidant capacity of seeds were i) MTT assay by using mammalian cell culture experiments, ii) DPPH (1,1-Diphenyl-2-picrylhydrazyl) radical scavenging test, and iii) ABTS (2,2-Azinobis (3-ethylbenzothiazoline-6-sulfonic acid) radical-scavenging assay. In all these 3 assays applied, there was no consistent effect of the seed extracts with wide range of Se concentrations on the cell viability measured by the MTT assay or in terms of DPPH radical-scavenging or ABTS scavenging capacity. Expected high antioxidant capacity of seed extracts by increasing Se concentrations was not found under given conditions. The reasons for the ineffectiveness of Se-enriched seeds in improving antioxidant capacity might be related to i) the methods applied and/or ii) to the level of the expected increase in antioxidant capacity by Se. Possibly, the level of the expected increase in antioxidant capacity by Se is too low when compared to the inherent antioxidant capacity of seeds, and this difference could not be detected by the methods applied. In future antioxidant tests, attention should be paid to the isolated Se-proteins from seeds differing in Se concentrations.
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