Search

Vegetables are an ideal source of human Se intake; it is important to understand selenium (Se) speciation in plants due to the distinct biological functions of selenocompounds. In this hydroponic study, the accumulation and assimilation of selenite and selenate in pak choi ( Brassica rapa ), a vastly consumed vegetable, were investigated at 1-168 h with HPLC speciation and RNA-sequencing. The results showed that the Se content in shoots and Se translocation factors with selenate addition were at least 10.81 and 11.62 times, respectively, higher than those with selenite addition. Selenite and selenate up-regulated the expression of SULT1;1 and PHT1;2 in roots by over 240% and 400%, respectively. Selenite addition always led to higher proportions of seleno-amino acids, while SeO 4 2- was dominant under selenate addition (>49% of all Se species in shoots). However, in roots, SeO 4 2- proportions declined substantially by 51% with a significant increase of selenomethionine proportions (63%) from 1 to 168 h. Moreover, with enhanced transcript of methionine gamma-lyase (60% of up-regulation compared to the control) plus high levels of methylselenium in shoots (approximately 70% of all Se species), almost 40% of Se was lost during the exposure under the selenite treatment. This work provides evidence that pak choi can rapidly transform selenite to methylselenium, and it is promising to use the plant for Se biofortification.

In Brassica species, hydrolysis of (methylthio)glucosinolates produces sulfur-containing aglycons which have demonstrated anticancer benefits. Selenized Brassicaceae contain (methylseleno)glucosinolates and their selenium-containing aglycons. As a prelude to biological testing, broccoli, cauliflower, and forage rape plants were treated with sodium selenate and their tap roots, stems, leaves, and florets analyzed for selenoglucosinolates and their Se aglycons. Two new selenoglucosinolates were identified: glucoselenoraphanin in broccoli florets and glucoselenonasturtiin in forage rape roots. A new aglycon, selenoberteroin nitrile, was identified in forage rape. The major selenoglucosinolates were glucoselenoerucin in broccoli, glucoselenoiberverin in cauliflower, and glucoselenoerucin and glucoselenoberteroin in forage rape roots. In broccoli florets, the concentrations of selenglucosinolates exceeded those of their sulfur analogues. Fertilization with selenium slightly reduced (methylthio)glucosinolates and aglycons in the roots, but increased them in the florets, the leaves, and sometimes the stems. These discoveries provide a new avenue for investigating how consumption of Brassica vegetables and their organoselenides may promote human health.

The common selenium oxoanions selenite (SeO3(2-)) and selenate (SeO4(2-)) are toxic at intake levels slightly below 1 mg day(-1). These anions are currently monitored by a variety of traditional analytical techniques that are time-consuming, expensive, require large sample volumes, and/or lack portability. To address the need for a fast and inexpensive analysis of selenium oxoanions, we present the first microchip capillary zone electrophoresis (MCE) separation targeting these species in the presence of chloride, sulfate, nitrate, nitrite, chlorate, sulfamate, methanesulfonate, and fluoride, which can be simultaneously monitored. The chemistry was designed to give high selectivity in nonideal matrices. Interference from common weak acids is avoided by operating near pH 4. Separation resolution from chloride was enhanced to improve tolerance of high-salinity matrices. As a result, selenate can be quantified in the presence of up to 1.5 mM NaCl, and selenite analysis is even more robust against chloride. Using contact conductivity detection, detection limits for samples with conductivity equal to the background electrolyte are 53 nM (4.2 ppb Se) and 380 nM (30 ppb) for selenate and selenite, respectively. Analysis time, including injection, is ∼2 min. The MCE method was validated against ion chromatography (IC) using spiked samples of dilute BBL broth and slightly outperformed the IC in accuracy while requiring <10% of the analysis time. The applicability of the technique to real samples was shown by monitoring the consumption of selenite by bacteria incubated in LB broth.