Bioaccessibility of selenium after human ingestion in relation to its chemical species and compartmentalization in maize

Abstract

Selenium is a micronutrient needed by all living organisms including humans, but often present in low concentration in food with possible deficiency. From another side, at higher concentrations in soils as observed in seleniferous regions of the world, and in function of its chemical species, Se can also induce (eco)toxicity. Root Se uptake was therefore studied in function of its initial form for maize (Zea mays L.), a plant widely cultivated for human and animal food over the world. Se phytotoxicity and compartmentalization were studied in different aerial plant tissues. For the first time, Se oral human bioaccessibility after ingestion was assessed for the main Se species (Se(IV) and Se(VI)) with the BARGE ex vivo test in maize seeds (consumed by humans), and in stems and leaves consumed by animals. Corn seedlings were cultivated in hydroponic conditions supplemented with 1 mg L(-1) of selenium (Se(IV), Se(VI), Control) for 4 months. Biomass, Se concentration, and bioaccessibility were measured on harvested plants. A reduction in plant biomass was observed under Se treatments compared to control, suggesting its phytotoxicity. This plant biomass reduction was higher for selenite species than selenate, and seed was the main affected compartment compared to control. Selenium compartmentalization study showed that for selenate species, a preferential accumulation was observed in leaves, whereas selenite translocation was very limited toward maize aerial parts, except in the seeds where selenite concentrations are generally high. Selenium oral bioaccessibility after ingestion fluctuated from 49 to 89 % according to the considered plant tissue and Se species. Whatever the tissue, selenate appeared as the most human bioaccessible form. A potential Se toxicity was highlighted for people living in seleniferous regions, this risk being enhanced by the high Se bioaccessibility.

A socio-scientific analysis of the environmental and health benefits as well as potential risks of cassava production and consumption

“…They reported that the concentrations of these metals in cassava roots grown in petroleum-impacted soil were significantly higher than those in the corresponding control soil. They also observed that metal concentrations in the cassava strongly depended on the concentration in the soil and that the concentrations varied between the different parts of the plant as observed by Mombo et al (2016). Similarly, Kříbek et al (2014) also reported higher concentrations of various metals (Cu, Co, Zn, As, and Pb) in cassava leaves than in stems and roots.…”

“…TME trace metal element. By Mombo et al (2016) germination, root elongation, biomass, and inhibition of chlorophyll biosynthesis (Pourrut et al 2011;Austruy et al 2014). Heavy metal phytotoxicity in plants depends on numerous physiological and molecular functions of the metal and crop, such as the following: (i) uptake and binding to root exudates and cell wall constituents; (ii) chelation and complexation of metal ions by various substances such as phytochelatins, glutathiones, metallothioneins, amino acids, and organic acids; and (iii) activation of plant defense systems for proper functioning of metabolic pathways (Shahid et al 2013).…”

“…The main source of environmental contamination in regard to cement production is related to the emission of dust and gas (Bilen 2010;Hindy et al 1990). Several recent studies concerning TME transfer in plants and their human bioaccessibility have revealed serious risks associated with growing food crops in areas of high atmospheric micronic and sub-micronic particle pollution (Uzu et al 2009;Mombo et al 2016). Edori et al (2015) reported that automobile exhaust emissions and roadside sediments (due to high heavy metal contents in soil) are the most likely sources of heavy metals in gari.…”

“…Persistent trace metal elements (TME) are frequently observed in anthropogenic areas with concentrations above the natural background levels (González et al 2015;Mombo et al 2015). The fate of these TME in terms of mobility, bioavailability, phyto-uptake, and compartmentation in different parts of the plant depends on both their chemical form (chemical speciation) and compartmentalization (Shahid et al 2011;Xiong et al 2014b;Mombo et al 2016). Furthermore, in African countries (south of the Sahara), farmers still widely use pesticides and herbicides (Ntow et al 2006) with little consideration for the environment and health concerns developed by REACH regulation (EC 1907(EC /2006 and food regulations in Europe (Onyedika and Nwosu 2008).…”

“…Cassava preparation before consumption to avoid the risk of exposure to cyanide. ByMombo et al (2016) …”