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Arsenic is a ubiquitous toxic metalloid causing serious health problems. Speciation analysis of arsenic in human urine provides valuable insights for large-scale epidemiological studies and informs on sources of exposure as well as human metabolism. The Multi-Ethnic Study of Atherosclerosis (MESA) is a valuable cohort for assessing chronic low-moderate arsenic exposure and health effects in an ethnically diverse US population. We present a state-of-the-art arsenic speciation analysis methodology and its application to 7677 MESA spot urine samples based on high-performance liquid chromatography coupled to inductively coupled plasma mass spectrometry. This method is fast, robust and detects a total of 11 individual As species at method detection limits of 0.02–0.03 μg arsenic/L urine for each individual species. Our analytical approach features excellent mean method accuracy (98%) and precision (5%) for the main arsenic species in urine (arsenobetaine, methylarsonic acid, dimethylarsinic acid, and total inorganic As); intra- (3–6%) and inter-day coefficients of variability (5–6%); column recovery (96 ± 7%); and spike recovery (97 ± 6%). The main arsenic species were detectable in ≥95% of urine samples due to the implementation of an oxidation step. Each individual minor arsenic species was detectable in ≤25% of all urines, although at least one of them was detected in almost half the participants. We identified two minor urinary arsenic species as dimethylarsinoylacetic acid and dimethylarsinoylpropionic acid, potential metabolites of seafood-related arsenicals. We observed differences in individual As species excretion by race/ethnicity, with Asian-American participants featuring 3–4 times higher concentrations compared to other participants. We also found differences by site, body mass index, smoking status, rice intake, and water arsenic levels, potentially indicating different exposures or related to individual bio-metabolism. The proposed approach is suitable for epidemiological studies and the collected data will constitute the base for future research on potential health effects of chronic low-level arsenic exposure. [Display omitted] • High-throughput arsenic speciation method for human urine developed and validated. • Identification of two minor urinary arsenic species by mass spectrometry. • 7677 spot urine samples analyzed in the Multi-Ethnic Study of Atherosclerosis. • Differences in arsenic species excretion observed across ethnic/racial groups. • Variations in urinary arsenic suggests diverse exposure sources or metabolic routes. [ABSTRACT FROM AUTHOR]

Environmental context: Arsenic is a globally distributed element, occurring in various chemical forms with toxicities ranging from harmless to highly toxic. We conducted 48-h cell culture experiments under batch and continuous conditions using the ubiquitous marine unicellular alga Dunaliella tertiolecta and evaluated the alga's arsenic metabolome over time. We found that the alga first methylates the inorganic As taken up from the surrounding water, and then further metabolises the intermediate simultaneously into more complex organo-arsenic molecules like sugars and lipids. These time series experiments are valuable pieces in the puzzle of how algae bio-metabolise arsenic, and in our understanding of the global arsenic cycle. Rationale: The uptake of arsenate by algae from oceanic waters and its transformation to arsenosugars and arsenolipids is well established, but the biosynthetic pathways remain largely unknown. Methodology: We investigated these pathways by using time-series experiments over 48 h to follow the formation of organoarsenic species from arsenate-enriched medium (15 µg As L−1) by the unicellular alga Dunaliella tertiolecta cultured under batch and continuous culture conditions. We used complementary mass spectrometry methods for the determination and quantification of 14 arsenic species; an additional three species could be quantified but remained unidentified. Results: The alga rapidly methylated the arsenate to dimethylarsinate (DMA), which then served as the precursor to arsenosugars and arsenolipids; the concentrations of these complex organoarsenicals increased throughout the experiments accompanied by a concomitant reduction in DMA concentrations. The pattern of compounds formed by the alga was similar for both batch and continuous cultures, but the concentrations were 2–3-fold higher in the continuous culture samples and the increases with time were much clearer. Discussion: The data suggest that the arsenosugars and the arsenolipids were mostly formed simultaneously from DMA, although there was an indication that the arsenic phospholipids were at least partly also being formed from the arsenosugars. Overall, the data are consistent with a direct biosynthesis of DMA from arsenate by D. tertioleta , and thereafter a non-specific incorporation of DMA into commonly available alga metabolites encompassing various sugars and lipids. Environmental context. Arsenic is a globally distributed element, occurring in various chemical forms with toxicities ranging from harmless to highly toxic. We conducted 48-h cell culture experiments under batch and continuous conditions using the ubiquitous marine unicellular alga Dunaliella tertiolecta and evaluated the alga's arsenic metabolome over time. We found that the alga first methylates the inorganic As taken up from the surrounding water, and then further metabolises the intermediate simultaneously into more complex organo-arsenic molecules like sugars and lipids. These time series experiments are valuable pieces in the puzzle of how algae bio-metabolise arsenic, and in our understanding of the global arsenic cycle. [ABSTRACT FROM AUTHOR]

[Display omitted] • Oxo-arsenic hydrocarbons are the major arsenolipids in fresh salmon. • When salmon is cooked, thioxo-arsenic hydrocarbons are formed. • Food regulations need to consider the arsenic species present in cooked fish. Arsenic hydrocarbons, major arsenolipids occurring naturally in marine fish, have substantial cytotoxicity leading to human health-related studies of their distribution and abundance in foods. These studies have all investigated fresh foods; because most fish are cooked before being consumed, it is both food- and health-relevant to determine the arsenolipids present in cooked fish. We used HPLC/mass spectrometry to investigate the arsenolipids present in salmon (Salmo salar) before and after cooking by either baking or steaming. In raw salmon (total As 2.74 mg kg−1 dry mass, of which 6% was lipid-soluble), major arsenolipids were three arsenic hydrocarbons (oxo-AsHC 332, oxo-AsHC 360, and oxo-AsHC 404, ca 55% of total arsenolipids) and a band of unidentified less-polar arsenolipids (ca 40%), trace amounts of another four arsenic hydrocarbons and two thioxo analogs were also detected. During the cooking process, 28% of the oxo-AsHCs were converted to their thioxo analogs. Our study shows that arsenic hydrocarbons naturally present in fresh fish are partly converted to their thioxo analogs during cooking by either baking or steaming. The greater lipophilicity of the thioxo analogs could alter the mode of toxicity of arsenic hydrocarbons, and hence future food regulations for arsenic should consider the influence of cooking on the precise type of arsenolipid in fish. [ABSTRACT FROM AUTHOR]

Non-ribosomal peptides are one class of bacterial metabolites formed by gut microbiota. Intestinal resident Klebsiella oxytoca produces two pyrrolobenzodiazepines, tilivalline and tilimycin, via the same nonribosomal biosynthesis platform. These molecules cause human disease by genotoxic and tubulin inhibitory activities resulting in apoptosis of the intestinal epithelium, loss of barrier integrity and ultimately colitis. Here we report a fast, reliable, HPLC-HR-ESMS2 method for quantifying simultaneously the bacterial enterotoxins tilimycin and tilivalline in complex biological matrices. We synthesized and applied stable isotopically labeled internal standards for precise quantification of the metabolites. Sample preparation was optimized using clinical and laboratory specimens including serum, colonic fluid and stool. The developed method overcame the disadvantage of low selectivity by applying high resolution mass spectrometry in MS2 mode. High sensitivity and low interference from matrices were achieved and validated. We show that the approach is suitable for detection and quantification of the enterotoxic metabolites produced in vivo , in infected human or animal hosts, and in bacterial culture in vitro. Image 1 • Selective and sensitive HPLC-HR-ESMS2 method developed for bacterial metabolites. • Stable 15N-labeled tilimycin (TM) and tilivalline (TV) standards synthesized. • Effective extraction from complex fecal samples optimized. • Precise quantification of microbiota-derived enterotoxins achieved. • Method validated by spiking and standard addition experiments. [ABSTRACT FROM AUTHOR]

Arsenolipid concentrations were measured in 17 food composites prepared from 152 food items purchased in Shizuoka city, Japan, to (1) determine the food contributing to daily intake of arsenolipids, and (2) estimate the daily intake of arsenolipids. Analysis of arsenolipids was performed by high performance liquid chromatography-inductively coupled plasma mass spectrometry/electrospray ionization tandem mass spectrometry (HPLC-ICP-MS/ESI-MS-MS). Arsenic containing hydrocarbons (AsHCs), arsenic containing fatty acids (AsFAs), and arsenosugar phospholipids (AsSugPLs) were detected only in “algae” and “fish and shellfish” of the 17 food composites in a concentration range of 4.4–233 ng As/g fresh weight (fw). Two cytotoxic arsenolipids, AsHC332 and AsHC360, were detected in “algae” and “fish and shellfish” in the concentrations range of 33–40 ng As/g fw. The estimated average daily intake of AsHC332 and AsHC360 was ca 3000 and 360 ng As/person/day, or 50 and 6.0 ng As/kg bw/day, respectively. The present study indicated that arsenolipids from “algae” and “fish and shellfish” consumption contributed to the daily intake of toxic AsHCs, though the margin of exposure for the AsHC332 and AsHC360 does not appear to pose a health risk for the general Japanese population. [ABSTRACT FROM AUTHOR]

The As concentrations, along with 34 other elements, and the As speciation were investigated in wild-grown samples of the parasitic mushroom Tolypocladium ophioglossoides with inductively coupled plasma mass spectrometry (ICPMS) and high performance liquid chromatography coupled to ICPMS. The As concentrations were 0.070–3.44 mg kg−1 dry mass. More remarkable was the As speciation, where up to 56% of the extracted As were found to be an unknown As species, which was marginally retained under anion- and also cation-exchange conditions. After testing several different chromatographic settings, the compound was finally isolated and identified as 2-(sulfoxyethyl) trimethylarsonium ion (in short: arsenocholine- O -sulfate) with high resolution mass spectrometry. The compound was synthesized and further quantified in all investigated samples via ion-pair chromatography coupled to ICPMS. In addition to the high abundance of arsenocholine- O -sulfate in T. ophioglossoides , small amounts of this As species were also detected in one sample of the host mushroom, Elaphomyces asperulus. In a sample of another parasitic mushroom, Ophiocordyceps sinensis , arsenocholine- O -sulfate could not be detected, but the main species was another unknown compound that was oxidized to inorganic As(V) with hydrogen peroxide. This is the first discovery of arsenocholine- O -sulfate in nature. It is possible that it is present in many other organisms, at least in low concentrations, and just has not been detected there yet because of its unusual chromatographic behavior. The existence of arsenocholine- O -sulfate brings up questions again about the biotransformation pathways of As in the environment and the specific behavior of fungi. Image 1 • Arsenocholine- O -sulfate was discovered for the first time in nature. • Arsenocholine- O -sulfate was the main As species in Tolypocladium ophioglossoides. • Concentrations of As species and 35 elements were determined in T. ophioglossoides. • Hosts, Elaphomyces spp., show different elemental profiles than T. ophioglossoides. [ABSTRACT FROM AUTHOR]