Biofortification of common buckwheat microgreens and seeds with different forms of selenium and iodine.

BACKGROUND: The biofortification of crops can counteract human diseases, including selenium (Se) and iodine (I) deficiencies in the diet. Little is known about the effects of combinations of Se and I on microgreens and seeds, or on their accumulation in these tissues. The present study aimed to evaluate Se (SeO3 2- , SeO4 2- ) and I (I- , IO3 - ) biofortification of common buckwheat microgreens and seeds with respect to the effects of the addition of Se, I and Se + I on yield and on physiological and biochemical characteristics. RESULTS: In combination treatments, microgreens yield (600-800 g m-2 ) was 50-70% higher than for Se and I alone. The respiratory potential also increased by 60-120%. Fv /Fm was close to 0.8 in all samples. Se content [0.24 µg g-1 dry weight (DW)] was 50% higher for combination treatments than for Se and I alone. I content was highest for IO3 - treatment (216 µg g-1 DW) and decreased in combination treatments with Se by 50%. CONCLUSION: Biofortification of buckwheat microgreens with Se and I should be performed with care because there are synergistic and antagonistic effects of these elements with respect to their accumulation. IO3 - for the biofortification of microgreens should be kept low to prevent exceeding the recommended daily intake of I. © 2019 Society of Chemical Industry.

Is foliar enrichment of pea plants with iodine and selenium appropriate for production of functional food?

Pea (Pisum sativum L.) plants were sown in a field and foliar sprayed at blooming stage with solutions of different forms of iodine (I) - I- and IO3- and selenium (Se) - SeO32- and SeO42-. The possibility of enrichment of pea seeds to nutritionally important levels of both elements and their distribution through the plant parts were studied. To evaluate stress caused by application of I and Se, some morphological, physiological and biochemical characteristics were determined. The results showed elevated concentrations of both elements in all parts of pea plants. In seeds, I content was more than 6-fold higher, while Se content was up to 12-fold higher than in control plants. Although the plants were in good condition, some differences in pod characteristics and electron transport system activity were observed. Glutathione content was not affected by any treatment and only the I- + SeO42- combination decreased the amount of anthocyanins in plants.

Calcium oxalate druses affect leaf optical properties in selenium-treated Fagopyrum tataricum.

Plants of the genus Fagopyrum contain high levels of crystalline calcium oxalate (CaOx) deposits, or druses, that can affect the leaf optical properties. As selenium has been shown to modify the uptake and accumulation of metabolically important elements such as calcium, we hypothesised that the numbers of druses can be altered by selenium treatment, and this would affect the leaf optical properties. Tartary buckwheat (Fagopyrum tataricum Gaertn.) was grown outdoors in an experimental field. At the beginning of flowering, plants were foliarly sprayed with sodium selenate solution at 10 mg selenium L-1 or only with water. Plant morphological, biochemical, physiological and optical properties were examined, along with leaf elemental composition and content. Se spraying did not affect leaf biochemical and functional properties. However, it increased leaf thickness and the contents of Se in the leaves, and decreased the density of calcium oxalate druses in the leaves. Except Se content, Se spraying did not affect contents of other elements in leaves, including total calcium per dry mass of leaf tissue. Redundancy analysis showed that of all parameters tested, only the calcium oxalate druses parameters were significant in explaining the variability of the leaf reflectance and transmittance spectra. The density of CaOx druses positively correlated with the reflectance in the blue, green, yellow and UV-B regions of the spectrum, while the area of CaOx druses per mm2 of leaf transection area positively correlated with the transmittance in the green and yellow regions of the spectrum.

Seed soaking in I and Se solutions increases concentrations of both elements and changes morphological and some physiological parameters of pea sprouts.

Pea (Pisum sativum L., cv. 'Petit Provencal') seeds were soaked in solutions of different iodine (I) and selenium (Se) forms (1000 mg I L-1 and 10 mg Se L-1). Iodine and selenium content in different parts of pea sprouts, as well as morphological, biochemical and physiological characteristics were measured in sprouts. The results showed increased concentrations of both elements in sprouts grown from treated seeds. Soaking influenced the biomass and height of the sprouts. Significant differences between plants grown from treated seeds in comparison with control plants were also observed for electron transport system activity and concentrations of tocopherol and glutathione. On the other hand, the content of photosynthetic pigments and anthocyanins remained similar as in control plants. Potential photochemical efficiency of photosystem II was close to theoretical maximum 0.8 in all samples. From the pattern of changes of stress indicators we suppose that plants adapted to the stress earlier in the experiment, i.e. before they were sampled for physiological measurements.

The effect of selenium and UV radiation on leaf traits and biomass production in Triticum aestivum L.

UV radiation as an evolutionarily important environmental factor, significantly affects plants traits and alters the effects of other environmental factors. Single and combined effects of ambient UV radiation, its exclusion, and Se foliar treatments on Si concentrations and production of Si phytoliths in wheat (Triticum aestivum L.) cv. 'Reska' were studied. The effects of these treatments on growth parameters of the plants, structural and biochemical traits of the leaves, and interactions of the leaves with light, as Si incrustation is the first barrier to light at the leaf surface were also examined. Under ambient UV radiation and foliar treatment with 10mgL-1 sodium selenate solution, there was a trade-off between the plant investment in primary and secondary metabolism, as the production of UV-absorbing compounds was enhanced while photosynthetic pigment levels were reduced. Independent of Se treatment, ambient UV radiation lowered respiratory potential, Ca concentration, and leaf thickness, and increased Si concentration, Si phytoliths formation, and cuticle thickness. The Se treatment has little effect on plant traits and biomass production but it increased Se concentrations in the plants by >100-fold, independent of UV radiation. In combination with UV radiation Se strengthen the protection of plants against stress by increasing the amount of UV absorbing compounds, light reflectance and transmittance.

Sulphur interferes with selenium accumulation in Tartary buckwheat plants.

Tartary buckwheat (Fagopyrum tataricum Gaertn.) and common buckwheat (Fagopyrum esculentum Moench.) plants grown in the field were treated foliarly with 126 µM solutions of selenate and/or sulphate in order to study the effect of sulphur (S) on selenium (Se) concentration in plants. In both species, the concentration of Se in all plant parts was similar in control and S treated plants. In Tartary buckwheat the concentration of Se was higher in S and Se treated plants than in plants treated with Se alone. S was shown to enhance Se accumulation in Tartary buckwheat. It was also shown that it is possible to produce grain and herb of Tartary and common buckwheat containing appropriate amounts of Se for food without affecting the yield of the plants.

Selenium and its compounds in aquatic plant Veronica anagallis-aquatica.

The uptake, distribution and determination of Se and its compounds in macrophyte Veronica anagallis-aquatica were investigated. V. anagallis-aquatica and sediments were sampled in years 2009-2011 and in 2013 in three Slovenian watercourses flowing through an agricultural area, where addition of Se in feedstuffs has been performed for about 25 years. Se content in sediments were up to 0.86 µg g(-1) and in whole plant varied from 0.186 to 1.535 µg g(-1), all on dry weight basis. Se content were measured also in different plant parts; highest content were found in roots and lowest in stems. Separation of extractable Se compounds was performed by ion exchange chromatography and for on-line detection inductively coupled plasma-mass spectrometry was used. The results showed that only approximately 24% of Se in the macrophyte was extracted using enzyme Protease XIV. Extractable Se in plant parts varied from 10.5% in roots to 29.6% in leaves. Identification of Se(IV) and Se(VI) was achieved but no Se-amino acids were detected even at highest Se content. According to our results, we assume that 25 years of Se addition in feedstuff shows minimal impact on Se content in the selected agricultural area.

Polonium-210 and selenium in tissues and tissue extracts of the mussel Mytilus galloprovincialis (Gulf of Trieste).

Marine organisms such as mussels and fish take up polonium (Po) and selenium (Se), and distribute them into different cellular components and compartments. Due to its high radiotoxicity and possible biomagnification across the marine food chain Po-210 is potentially hazardous, while selenium is an essential trace element for humans and animals. The aim of this study was to investigate and compare the presence and extractability of the elements in the mussels Mytilus galloprovincialis collected in the Gulf of Trieste. The levels of Po-210 in the samples ranged from 220 to 400 Bq kg(-1) and of Se from 2.6 to 8.2 mg kg(-1), both on a dry matter basis. Using various extraction types and conditions in water, buffer or enzymatic media, the best extractability was obtained with enzymatic extraction (Protease XIV, 1h shaking at 40 °C) and the worst by water extraction (24 h shaking at 37 °C). 90% of Po-210 and 70% of Se was extractable in the first case versus less than 10% of Po-210 and less than 40% of Se in the second. Such evident differences in extractability between the investigated elements point to different metabolic pathways of the two elements. In enzymatic extracts Se speciation revealed three Se compounds (SeCys2, SeMet, one undefined), while Po-210 levels were too low to allow any conclusions about speciation.

Monitoring of selenium in macrophytes - the case of Slovenia.

This paper examines macrophytes from various locations in Slovenian streams for selenium (Se) content in an attempt to discover if Se contamination is present and if Se uptake varies between sampling sites. For this purpose, macrophytes and water from ten locations in the Notranjska and Central regions (Slovenia) with different land use in the catchment were sampled. To assess the environmental conditions of the streams the Riparian, Channel, and Environment (RCE) inventory was applied, which revealed that investigated stretches of streams fall into RCE classes III, IV and V. The concentration of Se in water at all locations was less than 1µgSeL(-1). The Se content in macrophytes differed between sampling sites, with the highest content of Se in samples from Zerovniscica stream and the lowest in samples from Lipsenjscica stream. The content of Se was the highest in moss samples (3038ngSeg(-1) DM) and in the amphibious species Veronica anagallis-aquatica (1507ngSeg(-1) DM).

Impact of selenium on mitochondrial activity in young Tartary buckwheat plants.

To investigate the impact of Se on Tartary buckwheat (Fagopyrum tataricum Gaertn.) plants, the plant foliage was sprayed with 10 mg Se(VI) L(-1) at the beginning of flowering. The Se was effectively assimilated by the plants and taken into the seeds, where its concentration was more than double that in untreated plants. The seeds were collected and sown to obtain the progeny of these Se-treated plants. To assess the physiological characteristics of control plants and these Se-treated progeny plants, the estimated respiratory potential via electron transport system (ETS) activity and the photochemical efficiency of photosystem II were measured. Three weeks after germination, the Se-treated progeny plants showed higher ETS activity compared to the controls. Through weeks 4 and 5, this high ETS activity approximately halved, and the difference in ETS activity seen at 3 weeks was lost. On the other hand, at week 4, the potential photochemical efficiency was higher in the Se-treated progeny plants than the controls. In adult plants, the leaves dry mass was significantly greater in the Se-treated progeny plants than the controls. This study demonstrates an impact of Se in Tartary buckwheat on the progeny plants of Se sprayed plants, as shown previously in pea plants.

The uptake and distribution of selenium in three aquatic plants grown in Se(IV) solution.

The uptake of Se(IV) by Myriophyllum spicatum, Ceratophyllum demersum and Potamogeton perfoliatus, and the effects of Se(IV) on their physiological and biochemical characteristics were studied. Plants were cultivated outdoors under semi-controlled conditions in water solution containing Na selenite (20 µg Se L(-1) and 10 mg Se L(-1)). The higher concentration of Se lowered the photochemical efficiency of PSII in all species studied, while the lower concentration had no effect on any species. The higher concentration of Se lowered respiratory potential in M. spicatum. The response of M. spicatum and C. demersum to Se(IV) regarding chlorophylls was variable, however in the majority of cases, there was a trend of increasing the amount of chlorophylls, while in P. perfoliatus the amount of chlorophyll a decreased. The concentration of Se in plants cultured in 10 mg Se(IV) L(-1) ranged from 436 to 839 µg Se g(-1) DM in M. spicatum, 319 to 988 µg Se g(-1) DM in C. demersum and 310 to 661 µg Se g(-1) DM in P. perfoliatus. The amount of soluble Se compounds in enzyme extracts of high Se treatment was 27% in M. spicatum, 41% in C. demersum and 35% in P. perfoliatus. Se compounds were determined using HPLC-ICP-MS. It was observed that the applied Se(IV) was mainly transformed to insoluble Se.

Selenium species and their distribution in freshwater fish from Argentina.

The distribution and speciation of selenium (Se) in freshwater fish (muscle and liver tissue) from lakes in Argentina was investigated. Three introduced species, brown trout (Salmo trutta), rainbow trout (Oncorhynchus mykiss) and brook trout (Salvelinus fontinalis), and one native species, creole perch (Percichthys trucha), were investigated. Values for total selenium in muscle ranged from 0.66 to 1.61 µg/g, while in the liver, concentrations were much higher, from 4.46 to 73.71 µg/g on a dry matter basis. Separation of soluble Se species (SeCys(2), selenomethionine (SeMet), SeMeSeCys, selenite and selenate) was achieved by ion exchange chromatography and detection was performed by inductively coupled plasma-mass spectrometry. The results showed that in fish muscle, from 47 to 55 % of selenium was soluble and the only Se species identified was SeMet, which represented around 80 % of soluble Se, while in the liver, the amount of soluble Se ranged from 61 to 76 % and the percentage of species identified (SeMet and SeCys(2)) was much lower and ranged from 8 to 17 % of soluble Se.

Selenium and its species in the aquatic moss Fontinalis antipyretica.

The ability of the widely distributed aquatic moss Fontinalis antipyretica to take up Se from water was studied. Nine locations in the Notranjska region (Slovenia) with different land use in the catchment were sampled for water and moss in the year 2010 in spring, summer and autumn. The concentrations of Se in water at all locations did not exceed 0.2 ng mL(-1). F. antipyretica took up Se in the range between 345 and 2250 ng g(-1). All results for Se are expressed on dry matter basis. The Se content varied depending on the location and season. The highest concentration (2250 ± 170 ng g(-1)) of Se was found in the Zerovniscica stream that flows through an agricultural area with dairy farming. The fraction of insoluble Se compounds in the residue after enzymatic hydrolysis using protease (XIV) was around 75%. Soluble Se compounds in the enzymatic extract of F. antipyretica were separated and measured using HPLC coupled to ICP-MS. Se(IV) and Se(VI) were found but no organic Se compounds were detected, even at the highest concentration.

Impact of intensive physical activity on selenium status.

Various biomarkers were used to assess selenium (Se) status during 3 months of basic military training in a group of recruits. Samples of whole blood and plasma or serum were taken from a group of conscripts three times: at the beginning (n = 15), in the middle immediately after a severely stressful physical activity (n = 15) and at the end of military training (n = 13). Selenium was determined in diet samples, blood, plasma and plasma protein fractions as selenoprotein P (SelP) and glutathione peroxidase (eGPx). Selenium was determined by hydride generation-atomic fluorescence spectrometry and fractionation of proteins performed by affinity chromatography. Total serum glutathione, erythrocyte and serum GPx activity were followed as well. The average Se intake was calculated according to meal consumption questionnaires and Se determined in composite diet samples, giving an assessed intake of 48 ± 10 µg/day. At all three samplings, the average blood Se concentration was within the framework of adequate supply (87 ± 12, 94 ± 15 and 80 ± 13 ng/g). Plasma Se was between 70 and 80 ng/g (71 ± 10, 79 ± 9 and 76 ± 10 ng/g), which is believed to enable the full expression of plasma GPx. The average shares of plasma Se proteins were 61 ± 6%, 58 ± 6% and 54 ± 9% for SelP and 27 ± 4%, 34 ± 7% and 29 ± 5% for GPx. Although the observed tendency of the increases of serum and erythrocyte GPx activities at the second and third samplings with respect to the first was statistically insignificant, it is still indicative of some protection against oxidative stress, while the decreasing SelP levels during training suggest a slowly decreasing biologically active selenium pool.

Dietary supply of selenium for adolescents in three residential care orphanages in Southern Ghana.

Adolescents require optimum dietary supply of the essential trace mineral selenium (Se); however the absence of reliable and accurate data on the dietary supply of selenium for the adolescent population in Ghanaian residential care orphanages have made it difficult for public health nutritionists to assess the adequacy of the dietary supply. The dietary supply of selenium for adolescents (12-15 years) in three residential care orphanages, (Osu, Tutu-Akwapim and Teshie), in Southern Ghana have been evaluated by sampling their 24-h duplicate diets (including water) for 7-consecutive days using the duplicate diet sampling technique. The mass fraction of selenium in the blended lyophilized homogenates of duplicate diets was determined by radiochemical neutron activation analysis (RNAA). The validity of the RNAA method for selenium determination was checked by analyses of NIST SRM 1548a (Typical diet). The chemical yield of the radiochemical separation was determined by spectrophotometry. The average mass fractions of selenium in the blended lyophilized 24-hour duplicate diets for Osu, Tutu-Akwapim and Teshie were; 165±61 [117.2-285.2], 203±68 [110.5-304.9] and 250±92 [128.8-408.0]ng Seg(-1) lyophilized matter respectively. The average dietary supply of Se were, 57.6±17.3 [42.2-88.4], 82.0±30.7 [44.3-136.2] and 91.7±44.2 [46.0-153.4]µg Se day(-1) for Osu, Tutu-Akwapim and Teshie orphanages respectively. The data generated will help public health nutritionists in the provision of dietary advice and nutritional support for the studied orphanages, as well as other orphanages. The data will also help in the planning of institutional diets.

Maternal diet and selenium concentration in human milk from an Italian population.

BACKGROUND: Low selenium (Se) status is associated with several diseases. International organizations have proposed intakes of Se for general populations, including infants. Studies of the association of Se concentration in breast milk and maternal diet have yielded inconsistent results. We evaluated the relation between the intake of food items during pregnancy and Se concentration in human milk after delivery and compared infant intake of Se from breast milk with the recommended intakes. METHODS: This cross-sectional study was part of the baseline assessment of a prospective cohort of Italian mother-child pairs enrolled in 1999-2001. Se concentration was measured in the milk of 100 women included in the cohort and correlated with the intake of food items during pregnancy and lactation as reported in a food frequency questionnaire. RESULTS: Among foods consumed in pregnancy, only eggs had a positive, but weak, correlation with Se concentration in milk (r = 0.20, P = 0.04). Fish intake during lactation was also weakly correlated with Se in milk (r = 0.21, P = 0.04). Se content of breast milk in our population was lower than that noted in other international studies; however, very few children who were exclusively breastfed were estimated not to have met the recommended Se intake. CONCLUSIONS: Future research should aim to verify whether infants in this part of Italy still meet the recommended nutrient intake of Se and to assess the influence of the concurrent diet of lactating mothers on the Se content of their milk.

Stability of Se species in plant extracts rich in phenolic substances.

Since there is growing awareness of the strong dependence of the antioxidative function of selenium (Se) upon its chemical form, the stability of Se species during sample preparation is an important factor in obtaining qualitative and quantitative results. Many plant samples are rich in phenolic compounds (antioxidants), but data about their effect on specific Se species in extracts of plant samples are scarce. Therefore, the aim of this study was to investigate the effect of the most common phenolic substances in plant parts, namely tannin and the flavonoid rutin, on the concentration and/or transformation of several Se species (SeMet, SeCys(2), SeMeSeCys, Se(VI) and Se(IV)) during sample preparation (24 h incubation at 37 degrees C) and storage (4 days at 4 degrees C). Moreover, the effect observed was then studied in a real sample, buckwheat, because this plant is known as a rich source of phenolics, especially tannin and rutin. Se speciation was carried out by on-line coupling of ion-exchange HPLC-ICP-MS after water and enzymatic (protease) hydrolysis. The results showed that the ratio between the two antioxidants has an important role. When the antioxidants were present together, the response for Se(IV) was observed to start to decrease only at a ratio of rutin to tannin of 1:100 (w/w), indicating the ratio between antioxidants in buckwheat seeds. After water extraction, only 40% and after enzymatic extraction 80% of Se(IV) remained, but no other Se compound was detected with the system used. Furthermore, the extracts were not stable during storage at 4 degrees C. Signals for other Se species were stable. The results obtained for buckwheat seeds showed a decrease in Se(IV) response during sample preparation and storage, comparable to the one obtained with the experiments performed in vitro. However, Se species in extracts of other buckwheat parts (leaves, stems and sprouts) were stable. These results indicate that reactions in the extraction process and during storage may affect Se speciation and may result in misidentifications and inaccurate values.

How Safe are Antioxidant Food Supplements Containing Selenium?

Three antioxidant food supplements were analysed for selenium (Se) and its species. Sample A main constituents were coenzyme Q10, selenium (as medical yeast), vitamin C and natural vitamin E. The product is used for maintaining health and strengthening physical and mental abilities, stimulating the immune system, inhibiting the development of atherosclerosis, strengthening a weakened heart. Sample B main constituents were coenzyme Q10, selenium, vitamin E and beta-carotene. The product is advertised as high dosage natural coenzyme Q10, which provides supply of energy to all cells of human body. Sample C main ingredients were coenzyme Q10, selenium (as sodium selenite), beta-carotene and vitamin E with the same positive effects described as for the samples A and B. The samples were digested and analysed for Se content by hydride generation atomic fluorescence spectrometry (HG-AFS). For Se speciation, enzymatic hydrolysis with the enzyme protease was performed and soluble Se species was determined by ion-exchange chromatography coupled with inductively coupled plasma mass spectrometry (HPLC-ICP-MS). The results showed that the value of Se obtained for one of the products (C) far exceeded the declared value; instead of 10 µg Se per capsule, 69 µg of Se per capsule was found. The declared Se species in the same product was sodium selenite, but only SeCys2 was detected (55% of the total Se). In product B that did not have a declared Se form added, we detected 60% of total Se as selenite. In product A 75% of total Se was present as SeMet. It is worrying that the Se species determined and declared were different in two selected antioxidant food supplements.

Selenium and its species distribution in above-ground plant parts of selenium enriched buckwheat (Fagopyrum esculentum Moench).

Common buckwheat (Fagopyrum esculentum Moench) was foliarly sprayed with a water solution containing 10 mg Se(VI) L(-1) at the beginning of flowering. The total Se content in plant parts in the untreated group was low, whereas in the Se-sprayed group it was approximately 50- to 500-fold higher, depending on the plant part (708-4231 ng Se g(-1) DM(-1) (DM: dry matter)). We observed a similar distribution of Se in plant parts in both control and treated groups, with the highest difference in Se content being in ripe seeds. Water-soluble Se compounds were extracted by enzymatic hydrolysis with protease XIV, resulting in above 63% of soluble Se from seeds, approximately 14% from stems, leaves and inflorescences and less than 1% from husks. Se-species were determined in enzymatic extracts using HPLC-UV-HG-AFS (HPLC-hydride generation-atomic fluorescence spectrometry with UV treatment). The main Se species found in seeds was SeMet ( approximately 60% according to total Se content), while in stems, leaves and inflorescences the only form of soluble Se present was Se(VI) (up to 10% of total Se). In husks no Se-species were detected. We observed an instability of Se(IV) in seed extracts as a possible consequence of binding to the matrix components. Therefore, special care concerning sample extraction and the storage time of the extracts should be taken.

Saccharomyces cerevisiae: the effect of different forms and concentrations of iodine on uptake and yeast growth.

The essentiality of iodine for humans, especially in the early stages of life, is well recognized. The chemical forms of iodine in food supplements, infant formulae and iodated salt are either iodide (KI) or iodate (KIO(3)). Because there are no or rare data about iodine uptake by yeasts, we investigated the influence of different sources of iodine, as KI, KIO(3) and periodate (KIO(4)), on its uptake in and growth of the model yeast Saccharomyces cerevisiae. KIO(3) inhibited the growth of the yeast the most and already at a 400 microM initial concentration in the growth medium; the OD was reduced by 23% in comparison with the control, where no KIO(3) was added. The uptake of different iodine sources by the yeast S. cerevisiae was minimal, in total <1%. Tracer experiments with radioactive (131)I added as KI showed that the yeast S. cerevisiae does not have the ability to transform KI into volatile species. We investigated the specificity of iodine uptake added as KIO(3) in the presence of Na(2)SeO(4) or ZnCl(2) or K(2)CrO(4) in the growth medium, and it was found that chromate had the most influence on reduction of KIO(3) uptake.