Two-dimensional HPLC coupled to ICP-MS and electrospray ionisation (ESI)-MS/MS for investigating the bioavailability in vitro of arsenic species from edible seaweed

Gut Microbiota Control the Bioavailability and Metabolism of Organoarsenicals of Seaweeds in Mice after Oral Ingestion

Edible seaweed consumption is an essential route of human exposure to complex organoarsenicals, including arsenosugars and arsenosugar phospholipids. However, the effects of gut microbiota on the metabolism and bioavailability of arsenosugars in vivo are unknown. Herein, two nori and two kelp samples with phosphate arsenosugar and sulfonate arsenosugar, respectively, as the predominant arsenic species, were administered to normal mice and gut microbiota-disrupted mice treated with the broad-spectrum antibiotic cefoperazone for 4 weeks. Following exposure, the community structures of the gut microbiota, total arsenic concentrations, and arsenic species in excreta and tissues were analyzed. Total arsenic excreted in feces and urine did not differ significantly between normal and antibiotic-treated mice fed with kelp samples. However, the total urinary arsenic of normal mice fed with nori samples was significantly higher (p < 0.05) (urinary arsenic excretion factor, 34-38 vs 5-7%), and the fecal total arsenic was significantly lower than in antibiotic-treated mice. Arsenic speciation analysis revealed that most phosphate arsenosugars in nori were converted to arsenobetaine (53.5-74.5%) when passing through the gastrointestinal tract, whereas a large portion of sulfonate arsenosugar in kelp was resistant to speciation changes and was excreted in feces intact (64.1-64.5%). Normal mice exhibited greater oral bioavailability of phosphate arsenosugar from nori than sulfonate arsenosugar from kelp (34-38 vs 6-9%). Our work provides insights into organoarsenical metabolism and their bioavailability in the mammalian gut.

Native mass spectrometry-based metabolomics identifies metal-binding compounds

Although metals are essential for the molecular machineries of life, systematic methods for discovering metal-small molecule complexes from biological samples are limited. Here, we describe a two-step native electrospray ionization-mass spectrometry method, in which post-column pH adjustment and metal infusion are combined with ion identity molecular networking, a rule-based data analysis workflow. This method enabled the identification of metal-binding compounds in complex samples based on defined mass (m/z) offsets of ion species with the same chromatographic profiles. As this native electrospray metabolomics approach is suited to the use of any liquid chromatography-mass spectrometry system to explore the binding of any metal, this method has the potential to become an essential strategy for elucidating metal-binding molecules in biology.

LC/ICP-MS AND COMPLEMENTARY TECHNIQUES IN BESPOKE AND NONTARGETED SPECIATION ANALYSIS OF ELEMENTS IN FOOD SAMPLES

Chemical elements speciation analysis of food samples has been among the most important scientific topics over the last decades. Food samples are comprised of high variety of chemical compounds, from which many can interact with metals and metalloids, forming complex elemental species with various influence on the human body. It is particularly important not only to determine the amount of certain chemical element in food sample but also to identify the form in which given element occurs in given sample. Employment of bespoke and nontargeted speciation methods, with the use of liquid chromatography inductively coupled plasma mass spectrometry (LC/ICP-MS) and complementary techniques, provides more complete picture on the metals and metalloids speciation in food. This review discusses issues concerning speciation analysis of metals and metalloids in food samples with the use of LC/ICP-MS as a leading technique in elemental speciation nowadays and a complimentary technique intended for their identification. © 2020 John Wiley & Sons Ltd. Mass Spec Rev.

The Need to Unravel Arsenolipid Transformations in Humans

The main source of arsenic exposure to humans worldwide is the diet, in particular, drinking water, rice, and seafood. Although arsenic is often considered toxic, it can exist in food as more than 300 chemical species with different toxicities. This diversity makes it difficult for food safety and health authorities to regulate arsenic levels in food, which are currently based on a few arsenic species. Of particular interest are arsenolipids, a type of arsenic species widely found in seafood. Emerging evidence indicates that there are risks associated with human exposure to arsenolipids (e.g., accumulation in breast milk, ability to cross the blood-brain barrier and accumulate in the brain, and potential development of neurodegenerative disorders). Still, more research is needed to fully understand the impact of arsenolipid exposure, which requires establishing interdisciplinary collaborations.

Arsenic speciation and bioaccessibility in raw and cooked seafood: Influence of seafood species and gut microbiota

Seafood is an important source of arsenic (As) exposure for humans. In this study, 34 seafood samples (fishes, shellfishes, and seaweeds) collected from different markets in China were analysed for total and speciated As before and after boiling. Furthermore, the As bioaccessibility was also assessed using a physiologically based extraction test combined with the Simulator of Human Intestinal Microbial Ecosystems. The results showed that the total As (tAs) contents of seaweeds (raw: 44.12; boiled: 31.13, μg·g^-1 dw) were higher than those of shellfishes (raw: 8.34; boiled: 5.14, μg·g^-1 dw) and fishes (raw: 6.01; boiled: 3.25, μg·g^-1 dw). Boiling significantly decreased the As content by 22.24% for seaweeds, 32.27% for shellfishes, and 41.42% in fishes, respectively (p < 0.05). During in vitro digestion, the bioaccessibility of tAs and arsenobetaine (AsB) significantly varied between the investigated species of seafood samples in gastric (G) and small intestinal phases (I) (p < 0.05). Higher tAs bioaccessibility (G: 68.6%, I: 81.9%) were obtained in fishes than shellfishes (G: 40.9%, I: 52.5%) and seaweeds (G: 31%, I: 53.6%). However, there was no significant differences in colonic phase (C) (p > 0.05). With the effect of gut microbiota, arsenate (As^Ⅴ) was transformed into monomethylarsonic acid (MMA) and arsenite (As^Ⅲ) in C. Moreover, as for seaweeds, an unknown As compound was produced.

Arsenic species and their transformation pathways in marine plants. Usefulness of advanced hyphenated techniques HPLC/ICP-MS and UPLC/ESI-MS/MS in arsenic species analysis

The growing popularity of algae as a foodstuff around the world raises concern for the safety of this food type with respect to arsenic content in algae. The need for determination of total arsenic content and arsenic speciation in algae food has become an important issue. In this paper we have developed a complete analytical procedure for arsenic determination in algae products comprised of 1) total arsenic (tAs) determination in native algae samples after digestion, 2) extraction of As species with the use of two extraction methods with three extracting agents, 3) extracted total arsenic (extracted tAs) determination in algae extracts, 4) bespoke As speciation, 4) mass balance estimation based on extracted tAs and bespoke As speciation results, 5) unknown arsenic (uAs) species identification. Two advanced hyphenated techniques, HPLC/ICP-MS and UPLC/ESI-MS/MS, were employed along with the HPLC/ICP-MS method validation. Total As content in edible algae samples was found to range from (19.28 ± 0.45) mg kg^-1 up to (72.6 ± 2.7) mg kg^-1. Bespoke arsenic speciation of edible algae samples has revealed the presence of some known inorganic and simple organic As compounds such as As(III) from <LOD to (8.97 ± 0.59) mg kg^-1, As(V) from <LOD to (5.95 ± 0.29) mg kg^-1 and DMA from <LOD to (0.766 ± 0.040) mg kg^-1. Mass balance calculation carried out on the basis of tAs and bespoke As speciation results has shown that the amount of unknown As species in edible algae samples varied from 28% to 100% of extracted tAs. Identification of uAs species in edible algae samples has shown the presence of a high variety of As-sugars (12 compounds) and confirmed the presence of simple inorganic and organic As species such as As(V) and DMA along with 8 more simple organic As compounds. The results obtained in this study have confirmed that the high amounts of tAs do not correspond to the toxicity of algae based food due to the lack of the inorganic As in the tested samples.

Determination of inorganic arsenic in algae using bromine halogenation and on-line nonpolar solid phase extraction followed by hydride generation atomic fluorescence spectrometry

Accurate, stable and fast analysis of toxic inorganic arsenic (iAs) in complicated and arsenosugar-rich algae matrix is always a challenge. Herein, a novel analytical method for iAs in algae was reported, using bromine halogenation and on-line nonpolar solid phase extraction (SPE) followed by hydride generation atomic fluorescence spectrometry (HG-AFS). The separation of iAs from algae was first performed by nonpolar SPE sorbent using Br^- for arsenic halogenation. Algae samples were extracted with 1% perchloric acid. Then, 1.5mL extract was reduced by 1% thiourea, and simultaneously reacted (for 30min) with 50μL of 10% KBr for converting iAs to AsBr₃ after adding 3.5mL of 70% HCl to 5mL. A polystyrene (PS) resin cartridge was employed to retain arsenicals, which were hydrolyzed, eluted from the PS resin with H₂O, and categorized as iAs. The total iAs was quantified by HG-AFS. Under optimum conditions, the spiked recoveries of iAs in real algae samples were in the 82-96% range, and the method achieved a desirable limit of detection of 3μgkg^-1. The inter-day relative standard deviations were 4.5% and 4.1% for spiked 100 and 500μgkg^-1 respectively, which proved acceptable for this method. For real algae samples analysis, the highest presence of iAs was found in sargassum fusiforme, followed by kelp, seaweed and laver.

Algae as nutritional and functional food sources: revisiting our understanding

Global demand for macroalgal and microalgal foods is growing, and algae are increasingly being consumed for functional benefits beyond the traditional considerations of nutrition and health. There is substantial evidence for the health benefits of algal-derived food products, but there remain considerable challenges in quantifying these benefits, as well as possible adverse effects. First, there is a limited understanding of nutritional composition across algal species, geographical regions, and seasons, all of which can substantially affect their dietary value. The second issue is quantifying which fractions of algal foods are bioavailable to humans, and which factors influence how food constituents are released, ranging from food preparation through genetic differentiation in the gut microbiome. Third is understanding how algal nutritional and functional constituents interact in human metabolism. Superimposed considerations are the effects of harvesting, storage, and food processing techniques that can dramatically influence the potential nutritive value of algal-derived foods. We highlight this rapidly advancing area of algal science with a particular focus on the key research required to assess better the health benefits of an alga or algal product. There are rich opportunities for phycologists in this emerging field, requiring exciting new experimental and collaborative approaches.

The Emerging Role of Metalloproteomics in Alzheimer's Disease Research

Metals are increasingly recognized to have an important role in molecular processes underlying Alzheimer's disease (AD). This chapter discusses the current role of metals in AD and expands on the development of metalloproteomics and how the recent advances in analytical technology will allow detailed investigation of metalloproteins. Investigation of individual metalloproteins will yield new mechanistic details about the role of metals in AD.

Arsenic: bioaccessibility from seaweed and rice, dietary exposure calculations and risk assessment

Arsenic is a metalloid that occurs in food and the environment in different chemical forms. Inorganic arsenic is classified as a class I carcinogen. The inorganic arsenic intake from food and drinking water varies depending on the geographic arsenic background. Non-dietary exposure to arsenic is likely to be of minor importance for the general population within the European Union. In Europe, arsenic in drinking water is on average low, but food products (e.g. rice and seaweed) are imported from all over the world including from regions with naturally high arsenic levels. Therefore, specific populations living in Europe could also have a high exposure to inorganic arsenic due to their consumption pattern. Current risk assessment is based on exposure via drinking water. For a good estimation of the risks of arsenic in food, it is important to investigate if the bioavailability of inorganic arsenic from food is different from drinking water. The present study further explores the issue of European dietary exposure to inorganic arsenic via rice and seaweed and its associated health risks. The bioavailability of inorganic arsenic was measured in in vitro digestion experiments. The data indicate that the bioavailability of inorganic arsenic is similar for rice and seaweed compared with drinking water. The calculated dietary intake for specific European Union populations varied between 0.44 and 4.51 µg kg⁻¹ bw day⁻¹. The margins of exposure between the inorganic intake levels and the BMDL0.5 values as derived by JECFA are low. Decreasing the intake of inorganic arsenic via Hijiki seaweed could be achieved by setting legal limits similar to those set for rice by the Codex Alimentarius Commission in July 2014.

Desorption electrospray ionization mass spectrometry (DESI-MS) applied to the speciation of arsenic compounds from fern leaves

The different chemical forms of arsenic compounds, including inorganic and organic species, present distinct environmental impacts and toxicities. Desorption electrospray ionization mass spectrometry (DESI-MS) is an excellent technique for in situ analysis, as it operates under atmospheric pressure and room temperature and is conducted with no/minimal sample pretreatment. Aimed at expanding its scope, DESI-MS is applied herein for the quick and reliable detection of inorganic (arsenate--As(V): AsO4(3-) and arsenite--As(III): AsO2(-)) and organic (dimethylarsinic acid--DMA: (CH3)2AsO(OH) and disodium methyl arsonate hexahydrate: CH3AsO3·2Na·6H2O) arsenic compounds in fern leaves. Operational conditions of DESI-MS were optimized with DMA standard deposited on paper surfaces to improve ionization efficiency and detection limits. Mass spectra data for all arsenic species were acquired in both the positive and negative ion modes. The positive ion mode was shown to be useful in detecting both the organic and inorganic arsenic compounds. The negative ion mode was shown only to be useful in detecting As(V) species. Moreover, MS/MS spectra were recorded to confirm the identity of each arsenic compound by the characteristic fragmentation profiles. Optimized conditions of DESI-MS were applied to the analysis of fern leaves. LC-ICP-MS was employed to confirm the results obtained by DESI-MS and to quantify the arsenic species in fern leaves. The results confirmed the applicability of DESI-MS in detecting arsenic compounds in complex matrices.