Anne C. Kurilich

Variation in content of bioactive components in broccoli

The discovery of bioactive components in foods is exciting, suggesting the possibility of improved public health through diet. Yet the content of bioactive components in plant food varies, making quality control and intake recommendations problematic. Variation in content of bioactive components in fruits and vegetables depends upon both genetics and environment, including growing conditions, harvest and storage, processing and meal preparation. Cruciferous vegetables, which contain both anticarcinogenic and antioxidant properties, are excellent examples to illustrate the problem in assessing health benefits of foods that vary in content of bioactive components. In broccoli, the content of both glucosinolates and their bioactive hydrolysis products varies with genotype, environment and processing. Antioxidant vitamins and flavonoid content varies also. Here we review the influences of genetics, environment and post-harvest processing on content of bioactive components in broccoli, an area that is presently only partly understood. Reporting a range for bioactive component content can help the public to make informed choices about diet. For the future, research into the mechanisms behind this variation can lead to an understanding of genetic regulation of these variations, resulting in the generation of a consistent supply of nutritionally enhanced plant foods on the market.

Bioavailability of anthocyanins from purple carrot juice: effects of acylation and plant matrix.

Absorption of cyanidin-based anthocyanins is not fully understood with respect to dose or anthocyanin structure. In feeding studies using whole foods, nonacylated anthocyanins are more bioavailable than their acylated counterparts, but the extent to which plant matrix determines relative bioavailability of anthocyanins is unknown. Using juice of purple carrots to circumvent matrix effects, a feeding trial was conducted to determine relative bioavailability of acylated and nonacylated anthocyanins and to assess dose-response effects. Appearance of anthocyanins in plasma was measured in 10 healthy adults for 8 h following consumption of purple carrot juice. Each subject consumed 50, 150, and 250 mL of juice containing 76 micromol (65 mg), 228 micromol (194 mg), and 380 micromol (323 mg) of total anthocyanins, respectively. Acylated anthocyanins comprised 76% of total anthocyanins in the juice, yet their bioavailability was found to be significantly less than that of nonacylated anthocyanins. Peak plasma concentrations of nonacylated anthocyanins were 4-fold higher than that for acylated anthocyanins. Absorption efficiency declined across the doses administered. Because the treatments were consumed as juice, it could be discerned that the difference in bioavailability of acylated versus nonacylated anthocyanins was not primarily caused by interactions with the plant matrix.

SIMULTANEOUS QUANTIFICATION OF CAROTENOIDS AND TOCOPHEROLS IN CORN KERNEL EXTRACTS BY HPLC

An isocratic high performance liquid chromatographic (HPLC) method with run times of less than 22 min has been developed for simultaneous analysis of carotenoids and tocopherols in corn. The reverse phase system utilizes a nonaqueous mobile phase in combination with a polymeric C18 column coupled to a monomeric C18 column to separate lutein, zeaxanthin, β-cryptoxanthin, α-carotene, β-carotene, and the α-, δ- and γ- forms of tocopherol. The detector was a multi-channel UV-VIS. One channel was used to monitor carotenoid absorption at 450 nm while another monitored tocopherols at 290 nm. Retention times and spiked tests with known standards validated peak identification. Linear regressions of external standards generated coefficients of determination (R2) that were in the ninety-ninth percentile for all compounds tested. Using the same samples, concentrations generated from our protocol and compared with results from other laboratories suggest that this procedure is relatively accurate.