Organic Se Species Research Articles

Migration of l-Selenomethionine in the Water-Soil Interface Dominated by Iron Oxides.

Organic selenium (Se) accounts for up to 10-80% of total Se in soils, and l-selenomethionine (SeMet) is a typical organic Se species. However, the migration of SeMet in soils remains elusive. This study investigated the solid-liquid distribution, adsorption, desorption by phosphate, and self-oxidization of SeMet in solution under the influence of ferrihydrite, goethite, and hematite through batch experiments. Iron oxides could adsorb a much larger amount of SeMet than inorganic Se. At the initial Se element concentrations of 0-200 mg/L, the solid/liquid partition coefficient of SeMet was constant, which was 0.41, 0.43, and 0.50 on ferrihydrite, goethite, and hematite, respectively. In addition, the adsorption process of SeMet on the three iron oxides could be well described by the linear driving force model. Accordingly, the intraparticle diffusion coefficient of SeMet in ferrihydrite, goethite, and hematite was 1.4 × 103, 7.9 × 104, and 1.2 × 105 nm2/min, respectively. The adsorption of SeMet on the three iron oxides was slightly influenced by the pH and the coexisting ions, such as Cl-, NO3-, SO42-, and H2PO4-. The desorption ratio of SeMet on the three iron oxides by phosphate was lower than 2.5%. SeMet would aggregate the nanoparticles of iron oxides, resulting in a synergistic effect on the adsorption of phosphate. The oxidization ratio of SeMet was 23.9% in the solution, while it decreased to 17.1-17.5% in iron oxide suspensions. For this oxidization process, the three iron oxides exhibited varying effects to decelerate SeMet oxidation, as represented by the equivalent reaction. The findings of this study reveal the migration of SeMet in the water-soil interface under the influence of iron oxides, which can improve the understanding of Se cycling in the environment as well as provide some guidance for the better utilization of Se in soils and environmental remediation of Se pollution.

Molecular Mechanisms of the Effects of Sodium Selenite on the Growth, Nutritional Quality, and Species of Organic Selenium in Dandelions

Selenium (Se) is an essential trace element for the human body, and its dietary deficiency has been a widespread issue globally. Vegetables serve as a significant source of dietary Se intake, with organic Se derived from plants being safer than inorganic Se. In the present study, Taraxacum mongolicum plants were treated with various concentrations of Na2SeO3. The results showed that as the concentration of Na2SeO3 increased, the chlorophyll content of dandelion seedlings decreased at high concentrations, and the content of soluble sugars, soluble proteins, flavonoids, total phenols, and Vc all increased. The application of Na2SeO3 at concentrations ranging from 0 to 4 mg/L resulted in a reduction in plant malondialdehyde content and an enhancement in the activity of antioxidant enzymes. Following the Na2SeO3 treatment, five Se species were identified in the seedlings, Se4+, Se6+, selenocysteine, selenomethionine, and methylselenocysteine. Notably, selenomethionine emerged as the primary organic Se species in the shoots of dandelion. Transcriptome analysis revealed that ABC11b, PTR4, MOCOS, BAK1, and CNGC1 were involved in the absorption, transport, and storage of Se in dandelion, and C7317 was involved in the scavenging of reactive oxygen species. This study complements the understanding of the possible molecular mechanisms involved in the absorption and transformation of organic Se by plants, thereby providing a theoretical foundation for the biofortification of dandelion with Se in crops.

Characterization of Selenium Speciation in Se-Enriched Crops: Crop Selection Approach.

Accurately quantifying selenium (Se) speciation and transformation in Se-enriched crops is highly significant for human health. The investigation of Se species in Se-enriched crops involves assessing the enrichment of both organic and inorganic Se species, considering their plant families and edible parts. The staple crops of rice, corn, and wheat showed no or less inorganic Se with the increase of total Se; however, potatoes expressed a proportion of selenate [Se(VI)]. In addition, the organic Se proportions in Se-enriched crops of Cruciferous, Brassicaceae, and Umbelliferae plant families were relatively lower than the proportion of inorganic Se. Concurrently, the edible parts of the Se-enriched gramineous or cereal crops enriched with organic Se and crops with fruit, stem, leaf, and root as edible parts contain the maximum percentage of organic Se with a certain proportion of inorganic Se. This study contributes to a sparse body of literature by meticulously discerning appropriate Se-enriched crop selection through a comprehensive evaluation of Se speciation and its organic and inorganic accumulation potential.

The Ozonolysis of Methylated Selenide Compounds in the Atmosphere: Isotopes, Kinetics, Products, and Mechanisms.

Selenium (Se) is an essential micronutrient with an important atmospheric component in its biogeochemical cycle. In this cycle, phytoplankton form volatile organic Se species, such as dimethyl selenide (CH3SeCH3) and dimethyl diselenide (CH3SeSeCH3), which are emitted into the atmosphere. To predict the atmospheric fate of these methylated Se compounds, we investigated their ozonolysis reaction. We used proton-transfer-reaction time-of-flight mass spectrometry to quantify atmospheric Se and its isotopes, and used this method in kinetic and product studies. The ozonolysis of CH3SeCH3 proceeded with a rate constant of (7.4 ± 2.2) × 10-17 cm3 molec-1 s-1 at 26 ± 1 °C with an activation energy of 50 ± 14 kJ mol-1 forming dimethyl selenoxide (CH3Se(O)CH3). Comparatively, CH3SeSeCH3 reacted with O3 at (2.6 ± 0.9) × 10-17 cm3 molec-1 s-1 at 27 ± 1 °C with an activation energy of 56 ± 5 kJ mol-1 forming methylselinic acid (CH3Se(O)OH). At 20 ppbv of O3, the atmospheric lifetimes of CH3SeCH3 and CH3SeSeCH3 are 7.6 and 22 h, respectively. The Se oxidation products were confirmed by synthesis and can serve as new atmospheric tracers of methylated Se compounds. Overall, we measured Se isotopes in real time and determined the rate constants, activation energies, and oxidation products. These mechanisms can now be used to determine the quantitative atmospheric fate of Se toward O3, and thus its distribution within a changing climate.

Selenium contents, speciation and bioaccessibility of Se-enriched rice grains from Chinese markets

Diet intake accounts for >90% of selenium (Se) exposure in humans, with rice being the main source of Se intake for >60% of the Chinese population. In this study, 48 rice grain samples labeled Se-enriched were obtained from 22 major rice producing areas in China through online sources. Their total Se contents, Se speciation, and Se bioaccessibility were evaluated to provide a holistic view of Se-enriched rice in the market. The total Se contents were 0.006–0.951 ​μg ​g−1 (average 0.249 ​μg ​g−1), which showed great regional variations, with 73% of the samples satisfying the Se-enriched standard based on GB/T22499-2008 (0.04–0.30 ​mg ​kg−1). Over 80% of Se in the rice samples was organic Se species including selenomethionine, selenocysteine and methylselenocysteine, with selenomethionine being the main Se species, accounting for 61–98%. Based on a modified physiologically-based extraction test (MPBET), the Se bioaccessibility in 33 selected samples was 8.05–49.6% (28.6%) in the gastric phase and 18.1–117% (82.5%) in the intestinal phase. Further, Se bioaccessibility was positively correlated with organic Se (r ​= ​0.89–0.93), but not with inorganic Se (selenite and selenate), suggesting that Se bioaccessibility depended on organic Se in these rice grains. The data call for re-evaluation of Se-enriched rice in the market. Further, the potential risk of long-term consumption of Se-enriched rice in the market towards human health should be studied.

Inorganic and Organic Selenium Speciation of Seleno-Yeasts Used as Feed Additives: New Insights from Elemental Selenium Determination.

Seleno-Yeasts (SY) used as feed additives are known to contain different Selenium (Se) species.Seleno-Yeasts has been shown, on previous analytical methods, to contain selenomethionine (SeMet), selenocysteine (SeCys), selenate (SeIV) and selenite (SeVI), and various other organic and inorganic Se forms identified but rarely quantified. A new advanced method has allowed elemental Se (Se0), an inorganic Se species, to be quantified, thereby obtaining better insight into the proportion of inorganic Se in SY products. The study aimed to quantify the Se0 in SY products and assess the proportion of inorganic Se in SY. The Se speciation of 13 fresh commercials SY from different suppliers and batches, was assayed for the total Se, inorganic Se species (SeIV, SeVI and Se0), and organic Se species (SeMet and SeCys). Results on total Se were in line with the expected Se concentrations for all evaluated samples. The proportion of Se present as Se0 ranged from 3.6% to 51.8%. The quantity of Se0 in the SY products, added to SeIV and SeVI, indicated an average proportion of inorganic Se of 14.2% for the 13 analyzed SY products. The proportion of Se as SeMet ranged from 19.0% to 71.8%, (average of 55.8%), and a large variability in the SeMet content was observed. The SeCys content was also variable, with an average of 3.8%, relative to the total Se. In conclusion, advances in the analytical characterization have revealed that SY products can have a significantly high proportion of inorganic Se, which could affect the bioavailability of Se from SY supplements and explain their variable and lower bio-efficacy than pure SeMet supplements, such as hydroxy-selenomethionine.

Exploring Effects of Exogenous Selenium on the Growth and Nutritional Quality of Cabbage (Brassica oleracea var. capitata L.)

Selenium (Se) is an important trace element in human and animal health. Approximately 0.5–1 billion people worldwide are facing Se deficiency which can result in various endemic diseases. Cabbage is one of the most popular vegetables and can accumulate Se through biofortification. Therefore, producing Se-enriched cabbage may be an effective method to alleviate Se deficiency. In this study, the effects of different concentrations of selenite application on the growth and nutritional quality of cabbage were investigated and the results showed that the growth of cabbage was promoted at low concentrations of selenite (0.1–0.4 mmol/L) but inhibited at high concentrations (0.8–1.6 mmol/L). Concentrations of 0.1–0.2 mmol/L of selenite induced the accumulation of primary metabolites (soluble proteins, soluble sugars, and free amino acids), representative secondary metabolites (ascorbic acid, glucosinolates, flavonoids, anthocyanins, and phenolic acids), and important antioxidant enzyme (glutathione peroxidase, catalase, and superoxide dismutase) activity to improve the nutritional quality of cabbages. In addition, a higher concentration (0.8–1.6 mmol/L) of selenite proved beneficial in the accumulation of total Se and representative organic Se in cabbages. The main organic Se species in cabbage were selenomethionine (SeMet), accounting for 12.10% of total Se, followed by selenocysteine (SeCys2), accounting for 2.96% of total Se. It is suggested that an appropriate dose of exogenous selenite could be selected for different production purposes in cabbage cultivation. These findings are helpful for us to deeply understand the effects of selenite on the growth and nutritional quality of cabbages and to provide reliable technical support for vegetable cultivation and Se biofortification.

Nutrichemical alterations in different fractions of multiple-harvest alfalfa (Medicago sativa L.) green biomass fortified with various selenium forms

Background and AimsWet processed alfalfa-based products can provide high-quality concentrated protein, also contain nutrients and phytochemicals. Agronomic fortification can increase selenium (Se) incorporation into green biomass. For this reason, the aim was to investigate how different forms of Se are incorporated into the green biomass of multiple-harvest alfalfa and how they affect the chemical quality of the processed product candidates.MethodsIn this research, alfalfa was enriched with three forms of selenium at different concentrations [selenate (Se(VI)); selenite (Se(IV)); and red elemental Se (Se0)]. The fortified green biomass was fractionated into leaf protein concentrate (LPC), fiber and phytoserum, and changes in selenium content and speciation, protein and phytochemical composition were determined.ResultsTotal Se content in alfalfa fractions drastically reduced within the four consecutive harvests, particularly for Se(VI) and Se(IV) forms, and significantly varied according to the Se treatments. Selenomethionine (SeMet) was the predominant organic Se species in LPC (35.7–246.0 µg g −1 DW) and fiber (9.0- 47.7 µg g −1 DW) fractions. Se-fortification induced considerable changes in the crude protein of LPC, which varied between 29—45 (m/m)%. Phytochemical composition markedly varied among Se-treatments. Besides several flavonoids, aglycones and glycosyl derivatives, apigenin glucuronide, and apigenin were the most abundant with a concentration up to 170.85 µg g −1 DW. Medicagenic acid concentration was below 1.86 µg g −1 DW in LPC.ConclusionsSe-enhanced alfalfa green biomass could provide functional products, such as LPC, for human and animal consumption with enhanced nutritional value, including Se, protein, and phytochemical contents.

Selenium-enriched plant foods: Selenium accumulation, speciation, and health functionality.

Selenium (Se) is an essential element for maintaining human health. The biological effects and toxicity of Se compounds in humans are related to their chemical forms and consumption doses. In general, organic Se species, including selenoamino acids such as selenomethionine (SeMet), selenocystine (SeCys2), and Se-methylselenocysteine (MSC), could provide greater bioactivities with less toxicity compared to those inorganics including selenite (Se IV) and selenate (Se VI). Plants are vital sources of organic Se because they can accumulate inorganic Se or metabolites and store them as organic Se forms. Therefore, Se-enriched plants could be applied as human food to reduce deficiency problems and deliver health benefits. This review describes the recent studies on the enrichment of Se-containing plants in particular Se accumulation and speciation, their functional properties related to human health, and future perspectives for developing Se-enriched foods. Generally, Se's concentration and chemical forms in plants are determined by the accumulation ability of plant species. Brassica family and cereal grains have excessive accumulation capacity and store major organic Se compounds in their cells compared to other plants. The biological properties of Se-enriched plants, including antioxidant, anti-diabetes, and anticancer activities, have significantly presented in both in vitro cell culture models and in vivo animal assays. Comparatively, fewer human clinical trials are available. Scientific investigations on the functional health properties of Se-enriched edible plants in humans are essential to achieve in-depth information supporting the value of Se-enriched food to humans.

Selenium speciation and characteristics of selenium-enriched crops in Guiyang seleniferous soil, southwestern China

Environmental context Elemental selenium plays an important role in maintaining human health and the growth of plants and animals. We studied the availability of selenium in soils and agricultural crops in Guiyang City, China, and found that the soil is selenium-rich and the crops are selenium-enriched. These results can help to understand and improve the development of mountain agriculture and rural revitalisation. Rationale Selenium (Se) is a critical element for both maintaining human health and the growth of plants and animals. The content of Se in crops is primarily determined by its speciation in soil. Therefore, the investigation of soil Se and its speciation has become a key focus of current research. Methodology In this study, taking a typical seleniferous area in Guiyang City as the study area, we investigated selenium speciation in Se-rich soil and its distribution characteristics in both soil and crops using atomic fluorescence spectroscopy (AFS) and a five-step extraction processing methods. Moreover, we further explored the key factors that affect the distribution of Se in soil. Results The findings are summarised as follows: (1) the Se content in all investigated samples met the standards of selenium-rich soil (0.40 mg/kg). The Se content in the soil surrounding crop roots ranged from 0.96 to 4.29 mg/kg, with an average value of 2.18 mg/kg. (2) Soil Se primarily existed in organic, residual, and iron and manganese oxide-binding species. The organic, sulfide-binding, and elemental Se species were the major contributors, accounting for an average of 47.00%, while the content of water-soluble, exchangeable, and carbonate-binding Se species was significantly lower. (3) Almost all crops, regardless of their types, were found Se-enriched, accounting for approximately 89.47% of the total crops in the study area. The average Se content was 0.35, 0.12, and 0.026 mg/kg in tea, rice, and corn, respectively. Discussion Varying soil physical–chemical properties, such as the content of soil organic matter content and pH levels, etc. can impact the distribution of Se in soil differently. These findings can serve as a scientific foundation for the effective utilisation of selenium-rich land resources in Guiyang city. They can also support and facilitate the development of modern specialty and high-efficiency mountain agriculture, ultimately contributing to rural revitalisation and the national implementation of the Big Ecology Strategy.

Effect of sulphur on selenium accumulation and speciation in Nannochloropsis oceanica

• Sulphur deplete and limiting conditions result in more Se accumulation in N. oceanica . • The dominant Se species in N. oceanica is selenomethionine (SeMet) (>97 %). • Se speciation in N. oceanica is SeMet > SeCys 2 > SeMeSeCys > Se. • Selenium enrichment in N. oceanica does not affect total fatty acids accumulation. Sulphur (S) and selenium (Se) are chemically similar. Once Se is taken up, it substitutes S in S-containing amino acids. This study investigated the effect of S on selenite accumulation in the microalga Nannochloropsis oceanica . [0–28 mM] S concentrations and selenite concentrations of 0 and 30 μM were tested. S concentrations of ≤ 3 mM led to decreased cell growth whereas cultures with ≥ 4 mM were not growth limited. Se accumulation increased up to 8-fold when using S ≤ 2 mM and decreased with S 28 mM. The average relative abundance of organic Se species was selenomethionine (SeMet) 98.2 %, selenocystine (SeCys 2 ) 1.4 % and selenomethyl selenocysteine (SeMeSeCys) 0.4 %. Total fatty acids were not affected by S limitation or Se presence. This is the first study on the effect of S on selenite accumulation, organic Se speciation of N. oceanica and its potential as an organic Se-enriched food/feed ingredient.

Selenium Accumulation and Speciation in Chickpea (Cicer arietinum) Impacted by S in Soils: Potential for Biofortification

Dietary selenium (Se) deficiency is a well-known global problem originating from food crops grown in Se-deficient soil. Agronomic Se biofortification is one of the suitable options to minimize Se deficiency. Sulfur (S) is chemically similar to Se, and the role of S on the uptake and transformation of Se in grain has not been resolved. Considering this, our study examines the influence of S on the speciation and accumulation of Se in two chickpea cultivars (Amber and PBA sheamer) grown in Se-deficient soil under glasshouse conditions. Two doses of S (0 and 14 mg kg–1) as sulfate and three doses of Se (0, 1, and 2 mg kg–1) as selenate (SeVI) were used in a randomized factorial design. The addition of SeVI increased the Se content in grain in both cultivars compared to the control treatment. Speciation of Se analysis in grain showed that most (85%) of the Se accumulated in chickpea grain in the organic forms of Se as SeCys and MeSeCys. At 2 mg/kg Se addition, the biomass and grain yield was significantly reduced (P < 0.01), while S addition tended to increase the yield. Inorganic Se was below 15%, primarily as SeVI. PBA Sheamer, a desi type and widely grown chickpea cultivar, showed the most significant proportion of organic Se species, SeCys (57%) and SeMeCys (40%). Application of S contemporarily with Se showed increased SeMeCys production in the grain of PBA Sheamer cultivar. These findings indicated that the accumulation and speciation of Se in chickpea grain was dependent on both Se and S fertilization.

Selenium cycling in a marine dominated estuary: Lake Macquarie, NSW, Australia a case study

Environmental context Knowledge of the fate of selenium in estuaries receiving inputs from coal-fired power stations is essential as these environments are important nursery habitats for marine life and selenium has been shown to cause fish and bird mortality and sublethal effects including oedema, chromosomal aberrations and reproductive success. Understanding selenium cycling allows risk assessment to be undertaken and appropriate action to protect resident organisms. Abstract The fate of selenium (Se) inputs from coal-fired power station operations in a marine dominated estuary, Lake Macquarie NSW, is explored, as well as Se toxicity, including sublethal and population effects. Selenium is rapidly adsorbed to sediments, and food webs are based on benthic food sources. Selenium is remobilised from sediments by volatilisation and diffusional processes following bioturbation. It is then transferred into food chains via benthic microalgae, deposit feeders and filter-feeding organisms processing suspended sediments. Historically, Se has been found to accumulate in fish to levels above those considered safe for human consumption. After the remediation of a major ash dam in 1995, Se inputs to Lake Macquarie have declined, and the Se concentrations of sediments have also reduced partially due to the deposition of cleaner sediment but also due to the formation of volatile dimethyl selenide. Bioturbation of oxidised surface sediments also results in the release of inorganic Se. In response to decreases in sediment Se concentrations, molluscs and fish Se concentrations have also reduced below deleterious levels, with most fish now being safe for human consumption. Selenium cycling involves the transformation of inorganic species (Se0, SeII, SeIV, SeVI) in sediments and the water column to dimethylselenide and dimethyl diselenide by bacteria with the accumulation of organic Se species in plant detritus (selenomethionine) and animals (selenomethionine and selenocysteine). Dissolved Se concentrations in Lake Macquarie, except near ash dam inputs, have always been well below those that cause toxicity. There is evidence based on Se sediment-spiking studies, however, that Se is probably causing sublethal effects. When undertaking risk assessments of Se, careful consideration should be given to understanding the fate of Se inputs and remobilisation into food webs as not all systems act in accordance with published studies that generally have high Se concentrations in the water column and phytoplankton-based food webs.

The Relevance of Plant-Derived Se Compounds to Human Health in the SARS-CoV-2 (COVID-19) Pandemic Era.

Dietary selenium (Se)-compounds accumulated in plants are essential for human metabolism and normal physiological processes. Inorganic and organic Se species can be readily absorbed by the human body, but are metabolized differently and thus exhibit distinct mechanisms of action. They can act as antioxidants or serve as a source of Se for the synthesis of selenoproteins. Selenocysteine, in particular, is incorporated at the catalytic center of these proteins through a specific insertion mechanism and, due to its electronic features, enhances their catalytic activity against biological oxidants. Selenite and other Se-organic compounds may also act as direct antioxidants in cells due to their strong nucleophilic properties. In addition, Se-amino acids are more easily subjected to oxidation than the corresponding thiols/thioethers and can bind redox-active metal ions. Adequate Se intake aids in preventing several metabolic disorders and affords protection against viral infections. At present, an epidemic caused by a novel coronavirus (SARS-CoV-2) threatens human health across several countries and impacts the global economy. Therefore, Se-supplementation could be a complementary treatment to vaccines and pharmacological drugs to reduce the viral load, mutation frequency, and enhance the immune system of populations with low Se intake in the diet.

Selenium in cereals: Insight into species of the element from total amount.

Selenium (Se) is a trace mineral micronutrient essential for human health. The diet is the main source of Se intake. Se-deficiency is associated with many diseases, and up to 1 billion people suffer from Se-deficiency worldwide. Cereals are considered a good choice for Se intake due to their daily consumption as staple foods. Much attention has been paid to the contents of Se in cereals and other foods. Se-enriched cereals are produced by biofortification. Notably, the gap between the nutritional and toxic levels of Se is fairly narrow. The chemical structures of Se compounds, rather than their total contents, contribute to the bioavailability, bioactivity, and toxicity of Se. Organic Se species show better bioavailability, higher nutritional value, and less toxicity than inorganic species. In this paper, we reviewed the total content of Se in cereals, Se speciation methods, and the biological effects of Se species on human health. Selenomethionine (SeMet) is generally the most prevalent and important Se species in cereal grains. In conclusion, Se species should be considered in addition to the total Se content when evaluating the nutritional and toxic values of foods such as cereals.

Selenium speciation and bioaccessibility in Se-fertilised crops of dietary importance in Malawi

The purpose of this research was to explore the speciation and bioaccessibility of native soil-derived selenium (Se) versus Se applied via fertiliser in the edible portions of maize, groundnut and cowpea grown in Malawi. Fertiliser-derived Se, applied as isotopically labelled selenate, contributed 88–97% of the total Se in the edible portions. Both soil and fertiliser-derived Se were transformed into similar species, with more than 90% of the extracted Se in an organic form. The main form of fertiliser-derived Se in grain was selenomethionine with an abundance of 92.0 ± 7.6% in maize, 63.7 ± 6.2% in cowpea and 85.2 ± 1.9% in groundnut. In addition, cowpea contained 32.7 ± 6.2% of Se-methyl-selenocysteine. The mean bioaccessibility of fertiliser-derived Se was 73.9 ± 8.5% with no statistically-significant difference across all crops despite some variation in speciation. Understanding the contribution of fertiliser-derived Se to the formation of organic forms of Se in crops is crucial, given that organic Se species are more bioaccessible than inorganic forms.

Co-application of Se and a biostimulant at different wheat growth stages: Influence on grain development

An appropriate selenium intake can be beneficial for human health. Se-biofortified food in Se-deficient regions is becoming an increasingly common practice but there are still issues to be addressed regarding the observed Se-induced toxicity to the plant. In this respect, plant biostimulants are used to enhance nutrition efficiency, abiotic stress tolerance and crop quality. In this work, the efficacy of a plant biostimulant to counteract the Se-induced stress in wheat plants is experimentally assessed. The co-application of different Se-biofortification treatments and the biostimulant at different growth stages (tillering or heading stage) was investigated. The use of micro focused X-ray spectroscopy allows us to confirm organic Se species to be the main Se species found in wheat grain and that the proportion of organic Se species is only slightly affected by the Se application stage. Our study proves that the biostimulant had a key role in the enhancement of both the amount of grains produced per spike and their dry biomass without hindering Se enrichment process, neither diminishing the Se concentration nor massively disrupting the Se species present. This information will be useful to minimize both plant toxicity and economic cost towards a more effective and plant healthy selenium supplementation.

Quantitative selenium speciation in feed by enzymatic probe sonication and ion chromatography-inductively coupled plasma mass spectrometry

ABSTRACT A rapid, sensitive and species preservative analytical method for the simultaneous determination of six selenium (Se) species has been developed. Enzymatic probe sonication (EPS) was investigated as a novel and alternative technology for the extraction of Se species from feed matrices and the results were compared with the conventional hot water extraction, enzymatic hydrolysis and sequential extraction. The critical parameters of EPS such as enzyme types, extraction time, temperature, ultrasonic power and sample/enzyme ratio were varied with control. The Se species were separated and quantitatively determined by ion chromatography-inductively coupled plasma mass spectrometry (IC-ICP-MS). Under current optimised conditions, six inorganic and organic Se species were completely separated within 15 min in a single chromatographic run. The spectral interferences from the argon plasma 40Ar2, 40Ar37Cl or 1H79Br were effectively removed by employing the kinetic energy discrimination (KED) mode. Quantitative extraction for total Se (>94.8%) and more than 89.0% for the sum of different Se chemical forms without species transformation were obtained in only 60 s by applying the EPS treatment using aqueous protease XIV. The limits of detection (LODs) and quantification (LOQs) for Se species were in the ranges of 0.21–0.56 µg kg–1 and 0.69–1.87 µg kg–1, respectively. The proposed method was successfully applied to the speciation of Se in several reference materials and feed samples collected from the markets and local farms.

Microscale Investigation into Selenium Distribution and Speciation in Se-Rich Soils from Enshi, China.

In this study, we investigated the distribution and chemical speciation of Se in Se-rich soil by using micro-focused X-ray absorption near-edge structure (μ-XANES) spectroscopy coupling with X-ray fluorescence (μ-XRF) mapping. The microscale distribution showed that Se is heterogeneously distributed in the soil from seleniferous areas in Enshi, China. Se K-edge μ-XANES analysis suggested that Se is mainly present as Se(IV), organic Se(-II) or Se(0) species in Se-rich agricultural soil. The findings from this study would help improve the understanding of the fate, mobility, bioavailability, and biogeochemical cycling of Se in the seleniferous soil environment.

Grain Endogenous Selenium and Moderate Salt Stress Work as Synergic Elicitors in the Enrichment of Bioactive Compounds in Maize Sprouts

Salt stress and selenium are known to elicitate the production of plant secondary metabolites with antioxidant properties. On this basis, maize grains obtained from mother plants fertilized or not fertilized with selenium were sprouted at different levels of salinity (0, 25, and 50 mM NaCl) to evaluate the effects on the sprout yield, inorganic and organic Se species, minerals, and secondary metabolites, as revealed by a metabolomics analysis. Grain endogenous selenium (135 mg kg−1 vs. 0.19 mg kg−1 of the non-enriched grain) and salinity affected the sprout yield and composition, with salinity having the greatest effect on secondary metabolites. Most of the Se in sprouts was in an inorganic form, despite Se-enriched grains only containing organic Se. Some synergic effect was observed between Se and salinity. The best combination was obtained with Se-enriched grains sprouted at 25 mM NaCl, since this provided a good yield (not lower than in the untreated control), while sprout shoots were enriched in selenocystine and pro-nutritional semipolar compounds with antioxidant properties. Therefore, using grains from Se-fertilized crops and sprouting them under mild salt stress might represent a promising technique for improving the nutritional value of sprouts.