Antioxidant Potential in Broccoli and Observations on Flavor in a Segregating Broccoli Population (Brassica Oleracea)

201 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2001.Epidemiological studies indicate that broccoli consumption is inversely association with cardiovascular disease and cancer risk. Broccoli contains a number of bioactive compounds including glucosinolates, S-methyl cysteine sulfoxide (SMCSO) and many antioxidants that may be responsible for this protective effect. However, glucosinolates and SMCSO are also thought to negatively impact flavor and consumer acceptance of the vegetable, therefore increasing the level of these compounds in broccoli could be deleterious to its consumption. The antioxidant capacity of broccoli cultivars was investigated using the oxygen radical absorbance capacity (ORAL) assay and the dichlorofluorescin-diacetate (DCFH-DA) assay. The DCFH-DA assay was used to examine the antioxidant effects of broccoli extracts in HepG2 cells. The relationship between content of glucosinolates and SMCSO was also characterized in a broccoli population. ORAL assay findings indicated that water fractions of broccoli extracts had higher antioxidant capacity than lipid fractions and that cultivars varied in their antioxidant capacity. This variability was not associated with ascorbic acid or flavonoid content of the water fractions but was correlated with two carotenoids (lutein r = 0.57; zeaxanthin r = 0.81; p < 0.05) in the lipid fractions. DCFH-DA assay results showed that both water and lipid extracts of broccoli could significantly inhibit production of free radicals in HepG2 cells and that the effect was not correlated with ascorbic acid, flavonoid, carotenoid or tocopherol content. Correlation analysis between antioxidant capacity of broccoli extracts determined by ORAC or DCFH-DA showed that antioxidant capacity of water extracts from the ORAL assay correlated with antioxidant activity from DCFH-DA assay, but that for lipid extracts the ORAC assay could not predict antioxidant activity in cell culture. Results from the characterization of the relationship between glucosinolates, SMCSO and flavor indicated that glucosinolate content may have an impact on several flavor attributes, but SMCSO content did not affect broccoli flavor.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

β-Carotene Conversion to Vitamin A Decreases As the Dietary Dose Increases in Humans12

It has been suggested that high doses of β-carotene limit its conversion to vitamin A, yet this effect has not been well established in humans. A feeding study was conducted in a randomized crossover design in which volunteers consumed 2 doses of deuterium-labeled β-carotene on 2 occasions, with β-carotene and vitamin A response assessed by plasma area under the concentration time curve (AUC). Seven volunteers (4 men, 3 women) consumed each of 2 doses of β-carotene-d8 and provided serial blood samples for 37 d after each dose. β-Carotene doses were 20 and 40 mg. Plasma β-carotene-d8 was assessed by HPLC-MS. Plasma retinol (ROH)-d4, which was derived from the β-carotene-d8, was evaluated by GC-MS after saponification to convert retinyl esters to ROH prior to the formation of the trimethylsilylether. The plasma AUC for β-carotene-d8 increased 2-fold from the 20-mg dose to the 40-mg dose. The plasma AUC for ROH-d4 increased 36% from the 20-mg dose to the 40-mg dose. These results establish that, in humans, β-carotene conversion to vitamin A decreases as the dietary dose increases