Arsenobetaine Research Articles

Uptake and transformation of arsenic during the reproductive life stage of Agaricus bisporus and Agaricus campestris

Fruiting bodies from the Agaricus genus have been found to contain non-toxic arsenobetaine (AB) as a major compound. It is unknown whether AB is formed during the vegetative or reproductive life stages of the fungus, or by the surrounding microbial community, but AB's structural similarity to glycine betaine has led to the hypothesis that AB may be adventitiously accumulated as an osmolyte. To investigate the potential formation of AB during the reproductive life stage of Agaricus species, growth substrate and fungi were collected during the commercial growth of Agaricus bisporus and analyzed for arsenic speciation using HPLC-ICP-MS. AB was found to be the major arsenic compound in the fungus at the earliest growth stage of fruiting (the primordium). The growth substrate mainly contained arsenate (As(V)). The distribution of arsenic in an A. bisporus primordium grown on As(V) treated substrate, and in a mature Agaricus campestris fruiting body collected from arsenic contaminated mine tailings, was mapped using two dimensional XAS imaging. The primordium and stalk of the mature fruiting body were both found to be growing around pockets of substrate material containing higher As concentrations, and AB was found exclusively in the fungal tissues. In the mature A. campestris the highest proportion of AB was found in the cap, supporting the AB as an osmolyte hypothesis. The results have allowed us to pinpoint the fungus life stage at which AB formation takes place, namely reproduction, which provides a direction for further research.

Low-level environmental arsenic exposure correlates with unexplained male infertility risk

Humans are exposed to arsenic via drinking water, dietary intake and inhaled particulates. Endemic chronic arsenic exposure related reproductive toxicity is well documented, but the effect of low-level general environmental arsenic exposure on unexplained male infertility (UMI) remains unclear.In this case-control study, we aimed to investigate the relationship between non-geogenic environmental arsenic exposure and UMI risk. One hundred and one infertile men with normal semen as cases and sixty one fertile men as controls were recruited. Five urinary arsenic species: pentavalent arsenate (AsiV), trivalent arsenite (AsiIII), methylated to monomethylarsonic acid (MMAV), dimethylarsinic acid (DMAV), arsenobetaine (AsB) were quantitatively measured by liquid chromatography-inductively coupled plasma-mass spectrometry (LC-ICP-MS). To assess the semen quality, semen volume, sperm concentration, total motility, and progressive motility were measured.The nonparametric Mann-Whitney U test was used to compare the differences of arsenic species and index between the case and the control group; we observed that concentrations of AsiV, AsB, MMAV, DMAV, total inorganic As and total As were significantly higher in the cases than the controls. The urine AsiV level increased more than twenty folds in case group. Moreover, higher redox index (AsiV/AsiIII) and lower primary arsenic methylation index (PMI=MMAV/Asi) were observed for case group. Furthermore, through the logistic regression analysis, we observed that the urine AsiV level and PMI were most significantly associated with UMI risk among the observations. Specifically, in comparison to the first quartile, the subjects with higher AsiV levels were more likely to exhibit UMI with increasing adjusted odds ratios (AORs) (adjusted by age, body mass index, drinking status and smoking status) of 8.39 [95% confidence interval (CI), 2.59–27.17], 13.12 (95% CI, 3.44–50.12) and 36.51 (95% CI, 8.25–161.66) at the second, third and fourth quartiles, respectively. Also a concentration-dependent decrease of AOR was also observed for PMI in comparison to the fourth quartile: 15.43 [95% CI, 4.28–55.69], 9.69 (95% CI, 2.78–33.78) and 6.93 (95% CI, 2.21–21.76) at the first, second and third quartiles, respectively. These findings provide evidences that low-level environmental arsenic exposure was positively associated with UMI risk.

Arsenobetaine and thio-arsenic species in marine macroalgae and herbivorous animals: Accumulated through trophic transfer or produced in situ?

Arsenobetaine (AB) and thio-arsenoribosides were measured in common macroalgae species (8 phaeophyta, 4 rhodophyta and 2 chlorphyta), along the Australian south east coast line. As well, arsenic species profiles were measured for two common marine herbivores, the sea urchin Centrostephanus rodgersii and the fish Odax cyanomelas that graze on these macroalgae to understand if trophic transfer of these species would account for their presence in marine herbivores. AB was found in seven of the fourteen macroalgae species investigated but does not contributed significantly to any of the macroalgae arsenic content (0.01-1.2μg/g). AB was found in only two of the brown macroalgae and all the red and green macroalgae (with the exception of Corallina officinalis). Thio-arsenic species were found sporadically, but not in high concentrations in any of the macroalgae investigated. AB present in macroalgae is likely to be associated with epiphytic organisms while thio-arsenoribosides are likely to be produced by decaying parts of damaged macroalgae. A laboratory feeding experiment in which the herbivorous gastropod, Austrocochlea constricta, was fed macroalgae containing thio-arsenoribosides for a 24hr period every three days showed that these are readily accumulated over a short period. Thio-arsenoribosides in herbivores are therefore probably obtained through trophic transfer. Some AB is also obtained through trophic transfer; however, the presence of trimethylated arsonioribosides, a hypothesized precursor of AB formation in herbivores, suggests that some AB is produced within herbivores from the transformation of arsenoribosides accumulated from their diet.

Fractionation of inorganic arsenic by adjusting hydrogen ion concentration

The inorganic fraction of arsenic species, iAs=∑[As(III)+As(V)] present in fish samples can be quantified in the presence of other arsenic species also found in fishes, such as: monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and arsenobetaine (AsB). The toxic arsenic fraction was selected taking into account the dissociation constants of these arsenic species in different hydrogen ions concentration leading to the arsine formation from iAs compounds detected as As(III) by HG AAS. For thus, a microwave assisted extraction was carried out using HCl 1molL−1 in order to maintain the integrity of the arsenic species in this mild extraction media. Recovery experiments were done for iAs fraction, in the presence of other arsenic species. The recovery values obtained for iAs fraction added were quantitative about 87–107% (for N=3, RSD⩽3%). The limit of detection (LOD), and the limit of quantification (LOQ), were 5μgkg−1 and 16μgkg−1 respectively.

Arsenic and arsenic species in shellfish and finfish from the western Arabian Gulf and consumer health risk assessment

This study reports the levels of total arsenic and arsenic species in marine biota such as clams (Meretrix meretrix; N=21) and pearl oyster (Pinctada radiata; N=5) collected from nine costal sites in Jan 2014, and cuttlefish (Sepia pharaonis; N=8), shrimp (Penaeus semisulcatus; N=1), and seven commercially important finfish species (N=23) collected during Apr–May 2013 from seven offshore sites in the western Arabian Gulf. Total As and As species such as dimethylarsinic acid (DMA), arsenobetaine (AB), trimethylarsine oxide (TMAO), arsenocholine (AC), tetramethylarsonium ion (Tetra), arsenosugar-glycerol (As-Gly) and inorganic As (iAs) were determined by using ICPMS and HPLC/ICPMS. In bivalves, the total As concentrations ranged from 16 to 118mg/kg dry mass; the toxic iAs fraction contributed on average less than 0.8% of the total As, while the nontoxic AB fraction formed around 58%. Total As concentrations for the remaining seafood (cuttlefish, shrimp and finfish) ranged from 11 to 134mg/kg dry mass and the iAs and AB fractions contributed on average 0.03% and 81% respectively of the total As. There was no significant relationship between the tissue concentrations of total As and iAs in the samples. There was also no significant relationship between As levels in seafood and geographical location or salinity of the waters from which samples were collected. Based on our results, we recommend introducing a maximum permissible level of arsenic in seafood from the Gulf based on iAs content rather than based on total As. Our analyses of cancer risks and non-cancer hazards identified non-negligible risks and the potential for hazards; the greatest risks were identified for expatriate consumers of bivalves and high-end consumers of seafood. Despite this, many uncertainties remain that would be best addressed by further analyses.

Urinary arsenic profiles reveal exposures to inorganic arsenic from private drinking water supplies in Cornwall, UK.

Private water supplies (PWS) in Cornwall, South West England exceeded the current WHO guidance value and UK prescribed concentration or value (PCV) for arsenic of 10 μg/L in 5% of properties surveyed (n = 497). In this follow-up study, the first of its kind in the UK, volunteers (n = 207) from 127 households who used their PWS for drinking, provided urine and drinking water samples for total As determination by inductively coupled plasma mass spectrometry (ICP-MS) and urinary As speciation by high performance liquid chromatography ICP-MS (HPLC-ICP-MS). Arsenic concentrations exceeding 10 μg/L were found in the PWS of 10% of the volunteers. Unadjusted total urinary As concentrations were poorly correlated (Spearman’s ρ = 0.36 (P < 0.001)) with PWS As largely due to the use of spot urine samples and the dominance of arsenobetaine (AB) from seafood sources. However, the osmolality adjusted sum, U-AsIMM, of urinary inorganic As species, arsenite (AsIII) and arsenate (AsV), and their metabolites, methylarsonate (MA) and dimethylarsinate (DMA), was found to strongly correlate (Spearman’s ρ: 0.62 (P < 0.001)) with PWS As, indicating private water supplies as the dominant source of inorganic As exposure in the study population of PWS users.

Simultaneous separation and determination of six arsenic species in rice by anion-exchange chromatography with inductively coupled plasma mass spectrometry.

The simultaneous separation and determination of arsenite As(III), arsenate As(V), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenobetaine (AsB), and arsenocholine (AsC) in rice samples have been carried out in one single anion-exchange column run by high-performance liquid chromatography with inductively coupled plasma mass spectrometry. To estimate the effect of variables on arsenic (As) speciation, the chromatographic conditions including type of competing anion, ionic strength, pH of elution buffer, and flow rate of mobile phase have been investigated by a univariate approach. Under the optimum chromatographic conditions, baseline separation of six As species has been achieved within 10 min by gradient elution program using 4mM NH4 HCO3 at pH 8.6 as mobile phase A and 4mM NH4 HCO3 , 40mM NH4 NO3 at pH 8.6 as mobile phase B. The method detection limits for As(III), As(V), MMA, DMA, AsB, and AsC were 0.4, 0.9, 0.2, 0.4, 0.5, and 0.3μg/kg, respectively. The proposed method has been applied to separation and quantification of As species in real rice samples collected from Hunan Province, China. The main As species detected in all samples were As(III), As(V) and DMA, with inorganic As accounting for over 80% of total As in these samples.

Biotransformation of inorganic arsenic in a marine herbivorous fish Siganus fuscescens after dietborne exposure

Arsenic (As) is well known to be biodiminished along marine food chains. The marine herbivorous fish at a lower trophic level are expected to accumulate more As. However, little is known about how marine herbivorous fish biotransform the potential high As bioaccumulation. Therefore, the present study quantified the biotransformation of two inorganic As species (As(III) and As(V)) in a marine herbivorous fish Siganus fuscescens following dietborne exposure. The fish were fed on As contaminated artificial diets at nominal concentrations of 400 and 1500 μg As(III) or As(V) g−1 (dry weight) for 21 d and 42 d. After exposure, As concentrations in intestine, liver, and muscle tissues of rabbitfish increased significantly and were proportional to the inorganic As exposure concentrations. The present study demonstrated that both inorganic As(III) and As(V) in the dietborne phases were able to be biotransformed to the less toxic arsenobetaine (AsB) (63.3–91.3% in liver; 79.0%–95.2% in muscle). The processes of As biotransformation in rabbitfish could include oxidation of As(III) to As(V), reduction of As(V) to As(III), methylation to monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA), and subsequent conversion to AsB. These results also demonstrated that AsB synthesis processes were diverse facing different inorganic As species in different tissues. In summary, the present study elucidated that marine herbivorous fish had high ability to biotransform inorganic As to the organic forms (mainly AsB), resulting in high As bioaccumulation. Therefore, marine herbivorous fish could detoxify inorganic As in the natural environment.

Determination of Arsenic Species in Urine Samples of Subjects Not Exposed to Dietary Arsenic by High Performance Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometry

Arsenic (As) speciation in human urine was performed by anion exchange chromatography (AEC), followed by inductively coupled plasma mass spectrometry detection (ICP-MS). Separation of arsenite [As(III)], arsenate [As(V)], monomethylarsonic acid [MMA(V)L dimethylarsinic acid [DMA(V], arsenobetaine (AsB), and arsenocholine (AsC) in urine samples was accomplished in 9 minutes, resulting in quantification limits within the 0.3-0.9 ug L-1 range. The gradient elution program comprises two different mobile phases consisting of ultrapure water (phase A) and aqueous 20 mM nitric acid (phase B), both modified with 2% (v/v) methanol. Sample pre-treatment is based on human urine centrifugation (5000 rpm, 10 min), followed by filtration (0.45 μm) and dilution (1:4) with ultrapure water. Relative standard deviations (N=l 1) of the overall procedure were 8% for AsB and DMA(V), 11% for As(III), and 9% for MMA(V), As(V), and AsC. Arsenics quantification was performed using the standard addition method covering arsenic concentration ranges of 0-100 μ L-1 (expressed as arsenic) for all species. Germanium (5 μg L-1) was used as an internal standard. Analytical recoveries from the anion exchange column varied from 94 to 101% (urine sample spiked with low target concentrations), from 99-103% (urine sample spiked with intermediate target concentrations), and from 97-103% (urine sample spiked with high target concentrations). The developed procedure has been tested by analyzing the certified reference material NIST CRM 2669 Arsenic Species in Frozen Human Urine which offers certified contents for all arsenic species. After AEC and mass spectrometry detection, MMA(V), DMA(V), AsB, AsC, and also tetramethylarsonium ion (TETRA) were identified in several urine samples. The method has been applied to assess arsenic speciation in several human urine samples collected from volunteers not chronically exposed to arsenic via water and food.

MERCURY AND ARSENIC CONTENT IN SEAFOOD SAMPLES FROM THE JAKARTA FISHING PORT, INDONESIA

Mercury and arsenic are considered to be among the most toxic metals and have been associated with serious adverse health effects. These two trace metals and other contaminants that are found in fish products are therefore of public concern for food-safety reason. Hence, we selected three marine species to study i.e., yellow fin tuna, marlin and green mussels because of their economic values in the international and local markets. The objective of our study was to determine the arsenic and mercury content in these three marine species as a first step in monitoring metal content in seafood products. The tissue samples of tuna and marlin were collected from the Jakarta fishing port, while the green mussels was collected from aqua-culture sites in Jakarta Bay. The metal content was determined by ICP-MS and validated using CRM DORM-2 and DORM-3. The speciation of arsenic (organic and inorganic forms) was determined using HPLC-ICPMS.All measurements were based on dry weight samples. The result showed that the mercury concentration in yellow-fin tuna, marlin and green mussel samples was 0.68 ± 0.08 mg kg-1, 0.56 ± 0.06 mg kg-1 and 1.51 ± 0.10 mg kg-1, respectively. The total arsenic concentration in yellow-fin tuna, marlin and green mussel samples was 3.47 ± 0.21 mg kg-1, 2.71 ± 0.18 mg kg-1, and 6.77 ± 0.32 mg kg-1, respectively. The mercury content in the fish tissue was below the maximum allowable concentration (National Standard of Indonesia 1.0 mg kg-1), except for the green mussels. For total arsenic concentration, all the samples were above the national standard concentration (1.0 mg kg-1). The organic arsenic species arsenobetain (AB) found in tuna and marlin fish samples was not toxic. Inorganic and organic arsenic was found in the green mussel samples. Our results suggest that there is a need to establish a national program to regularly monitor the content of selected trace metals in fishery products.

Arsenic compounds occurring in ruderal plant communities growing in arsenic contaminated soils

Wild growing phytocenosis from three different areas near former gold or silver mines—Kutná Hora, Roudný and Nalžovské Hory (Czech Republic) were investigated for total arsenic and arsenic species concentrations. The most abundant plant families that occurred were Fabaceae, Lamiaceae, Asteraceae, Poaceae and Plantaginaceae. Several plant species such as Achillea millefolium L. (Asteraceae), Anthoxanthum odoratum L. (Poaceae), Plantago lanceolata L. (Plantaginaceae) are widespread and could be found in all of the investigated areas. Total As concentrations in aboveground biomass of plants growing on those three sites were determined by an inductively coupled plasma mass spectrometry (ICPMS) and ranged from 0.02*mgAskg−1 (Stellaria spp.) to 39.30±6.32mgAskg−1 (Daucus carota L.). The concentrations seem to be dependent on both plant species and physico-chemical soil properties. For the arsenic speciation a high performance liquid chromatography (HPLC) online connected with the ICPMS was used. Results have shown that arsenite and arsenate are the prevalent arsenic compounds. Methylarsonic acid (MA), dimethylarsinic acid (DMA), arsenobetaine (AB), arsenocholine (AC), tetramethylarsonium ion (TETRA), and trimethylarsine oxide (TMAO) were identified as minor species. Arsenobetaine was found at significant concentrations in Carex praecox Schreb. (28% of the extractable As amount) and P. lanceolata L. (1.2% of the extractable As amount).

Determination of 20 trace elements and arsenic species for a realgar-containing traditional Chinese medicine Niuhuang Jiedu tablets by direct inductively coupled plasma–mass spectrometry and high performance liquid chromatography–inductively coupled plasma–mass spectrometry

Niuhuang Jiedu tablet (NHJDT) is a realgar-containing traditional Chinese medicine. A direct inductively coupled plasma-mass spectrometry (ICP-MS) method for the simultaneous determination of 20 trace elements (Mg, K, Ca, Na, Fe, As, Zn, Sr, Ba, Cu, Mn, Ni, Pb, V, Cr, Se, Co, Mo, Cd, Hg) in NHJDT, as well as in water, gastric fluid and intestinal fluid was established. Meanwhile, a high performance liquid chromatography–inductively coupled plasma-mass spectrometry (HPLC–ICP-MS) method was developed for the determination of arsenite (AsIII), arsenate (AsV), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and for the identification of arsenobetaine (AsB) and arsenocholine (AsC) in these extracts. Both methods were fully validated in the respect of linearity, sensitivity, precision, stability and accuracy. The reliability of the ICP-MS method was further evaluated using a certified standard reference material prepared from dried tomato leaves (NIST, SRM 1572a). The analysis showed that some manufacturers formulated lower amount of realgar than required in the Chinese Pharmacopoeia (ChP) in their preparations. In addition, almost same extraction profiles for total As and inorganic As were found in water and in gastrointestinal fluids, while higher extraction rates for other 19 elements were observed in gastrointestinal fluids. Our findings show that the toxicities of Hg, Cu, Cd and Pb in NHJDP are low, while the real As toxicity in NHJDT should be deeply investigated.

Reversed Phase Column HPLC-ICP-MS Conditions for Arsenic Speciation Analysis of Rice Flour

New measurement conditions for arsenic speciation analysis of rice flour were developed using HPLC-ICP-MS equipped with a reversed phase ODS column. Eight arsenic species, namely, arsenite [As(III)], arsenate [As(V)], monomethylarsonic acid (MMAA), dimethylarsinic acid (DMAA), trimethylarsine oxide (TMAO), tetramethylarsonium (TeMA), arsenobetaine (AsB) and arsenocholine (AsC), were separated and determined under the proposed conditions. In particular, As(III) and MMAA and DMAA and AsB were completely separated using a newly proposed eluent containing ammonium dihydrogen phosphate. Importantly, the sensitivity changes, in particular those of As(V) and As(III) caused by coexisting elements and by complex matrix composition, which had been problematical in previously reported methods, were eliminated. The new eluent can be applied to C8, C18 and C30 ODS columns with the same effectiveness and with excellent repeatability. The proposed analytical method was successfully applied to extracts of rice flour certified reference materials.

Enzyme-assisted extraction and liquid chromatography mass spectrometry for the determination of arsenic species in chicken meat

Chicken is the most consumed meat in North America. Concentrations of arsenic in chicken range from μgkg−1 to mgkg−1. However, little is known about the speciation of arsenic in chicken meat. The objective of this research was to develop a method enabling determination of arsenic species in chicken breast muscle. We report here enzyme-enhanced extraction of arsenic species from chicken meat, separation using anion exchange chromatography (HPLC), and simultaneous detection with both inductively coupled plasma mass spectrometry (ICPMS) and electrospray ionization tandem mass spectrometry (ESIMS). We compared the extraction of arsenic species using several proteolytic enzymes: bromelain, papain, pepsin, proteinase K, and trypsin. With the use of papain-assisted extraction, 10 arsenic species were extracted and detected, as compared to 8 detectable arsenic species in the water/methanol extract. The overall extraction efficiency was also improved using a combination of ultrasonication and papain digestion, as compared to the conventional water/methanol extraction. Detection limits were in the range of 1.0–1.8μg arsenic per kg chicken breast meat (dry weight) for seven arsenic species: arsenobetaine (AsB), inorganic arsenite (AsIII), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), inorganic arsenate (AsV), 3-nitro-4-hydroxyphenylarsonic acid (Roxarsone), and N-acetyl-4-hydroxy-m-arsanilic acid (NAHAA). Analysis of breast meat samples from six chickens receiving feed containing Roxarsone showed the presence of (mean±standard deviation μgkg−1) AsB (107±4), AsIII (113±7), AsV (7±2), MMA (51±5), DMA (64±6), Roxarsone (18±1), and four unidentified arsenic species (approximate concentration 1–10μgkg−1).

Arsenic Speciation in Honeysuckle (Lonicera japonica Thunb.) from China.

In this study, honeysuckle, a common Chinese herbal medicine, produced from different areas was investigated for total arsenic and arsenic species concentration. The total arsenic concentrations were determined by inductively coupled plasma mass spectrometry (ICP-MS) and ranged from 275 to 635μgkg(-1). A microwave-assisted procedure with 1% phosphoric acid (v/v) was used for the extraction of arsenic species in honeysuckle. The total arsenic species concentration found by liquid chromatography-inductively coupled plasma mass spectrometry (LC-ICP-MS) was in agreement with the total arsenic concentration determined by the ICP-MS analysis after the microwave digestion. Arsenate (As(V)) with an average proportion of 54.3% was the predominant arsenic species in honeysuckle. The order of concentration is as follows: As(V) > arsenite (As(III)) > dimethylarsinic acid (DMA) > arsenobetaine (AsB) > monomethylarsonic acid (MMA). The proportion of organic arsenic (24.7%) was higher than that in most terrestrial plants. Moreover, the distributions of arsenic species in the honeysuckle from different producing areas were significantly different. This study provides useful information for better understanding of the distribution of arsenic species in terrestrial plants.

Development and validation of a simple and robust method for arsenic speciation in human urine using HPLC/ICP-MS.

In order to better distinguish the different toxic inorganic and organic forms of arsenic (As) exposure in individuals, we have developed and validated a simple and robust analytical method for determining the following six As species in human urine: arsenous (III) acid (As-III), As (V) acid, monomethylarsonic acid, dimethylarsinic acid, arsenobetaine (AsB), and arsenocholine. In this method, human urine is diluted using a pH 5.8 buffer, separation is performed using an anion exchange column with isocratic HPLC, and detection is achieved using inductively coupled plasma-MS. The method uses a single mobile phase consisting of low concentrations of both phosphate buffer (5 mM) and ammonium nitrate salt (5 mM) at pH 9.0; this minimizes the column equilibration time and overcomes challenges with separation between AsB and As-III. In addition, As-III oxidation is prevented by degassing the sample preparation buffer at pH 5.8, degassing the mobile phase online at pH 9.0, and by the use of low temperature (-70 °C) and flip-cap airtight tubes for long term storage of samples. The method was validated using externally provided reference samples. Results were in agreement with target values at varying concentrations and successfully passed external performance test criteria. Internal QC samples were prepared and repeatedly analyzed to assess the method's long-term precision, and further analyses were completed on anonymous donor urine to assess the quality of the method's baseline separation. Results from analyses of external reference samples agreed with target values at varying concentrations, and results from precision studies yielded absolute CV values of 3-14% and recovery from 82 to 115% for the six As species. Analysis of anonymous donor urine confirmed the well-resolved baseline separation capabilities of the method for real participant samples.

The formation and fate of organoarsenic species in marine ecosystems: do existing experimental approaches appropriately simulate ecosystem complexity?

Environmental context In marine environments, inorganic arsenic present in seawater is transformed to organoarsenic species, mainly arsenoribosides in algae and arsenobetaine in animals. These transformations decrease the toxicity of arsenic, yet the fate of arsenoribosides and arsenobetaine when marine organisms decompose is unknown. We review the current literature on the degradation of these organoarsenic species in marine systems detailing the drivers behind their degradation, and also discuss the environmental relevance of laboratory-based experiments. Abstract Despite arsenoribosides and arsenobetaine (AB) being the major arsenic species in marine macro-algae and animals they have never been detected in seawater. In all studies reviewed arsenoribosides from marine macro-algae were degraded to thio-arsenoribosides, dimethylarsinoylethanol (DMAE), dimethylarsenate (DMA), methylarsenate (MA) with arsenate (AsV) the final product of degradation. The use of different macro-algae species and different experimental microcosms did not influence the arsenoriboside degradation pathway. The use of different experimental approaches, however, did influence the rate and extent at which arsenoriboside degradation occurred. This was almost certainly a function of the complexity of the microbial community within the microcosm, with greater complexity resulting in rapid and more complete arsenoriboside degradation. AB from decomposing animal tissues is degraded to trimethylarsine oxide (TMAO) or dimethylarsenoacetate (DMAA), DMA and finally AsV. The degradation of AB unlike arsenoribosides occurs via a dual pathway with environmental or microbial community variability influencing the pathway taken. The environmental validity of different experimental approaches used to examine the fate of organoarsenic species was also reviewed. It was evident that although liquid culture incubation studies are cheap and reproducible they lack the ability to culture representative microbial communities. Microcosm studies that include sand and sediment are more environmentally representative as they are a better simulation of marine ecosystems and are also likely to facilitate complex microbial communities. An added benefit of microcosm studies is that they are able to be run in parallel with field-based research to provide a holistic assessment of the degradation of organoarsenic species in marine environments.

Sample Preparation Methods for Organic Arsenic Species (arsenobetain, (CH3)3As+CH2COO−) in Tuna Fish Samples Followed by HG-QFAAS, GF-AAS, and ICP-MS Measurements

Determination of total arsenic was strongly influenced by the properties of the spesies. In a sample of tuna fish, the total arsenic concentration (90-95%) mostly comes from organic arsenic species, arsenobetain (AB). AB in particular, was not decomposed to arsenate which can lead to a serious error in quantification when a hydride generator step is additionally used in the analysis scheme. This research was done to compare three different types of sample preparations, namely dry ashing, water extraction, and microwave digestion, for measuring the total arsenic using HG-QF-AAS, GF-AAS and ICP-MS measurements. HG-QF-AAS and ICP-MS gave similar concentrations of total arsenic in a tuna fish sample, which were 3.49±0.08μg g-1 and 3.56±0.014μg g-1, respectively. Meanwhile, the result from GF-AAS measurements was about a half of the others. The results of this research can be used as a reference for determination of total arsenic in tuna fish samples.

Contribution of arsenic species in unicellular algae to the cycling of arsenic in marine ecosystems.

This review investigates the arsenic species produced by and found in marine unicellular algae to determine if unicellular algae contribute to the formation of arsenobetaine (AB) in higher marine organisms. A wide variety of arsenic species have been found in marine unicellular algae including inorganic species (mainly arsenate--As(V)), methylated species (mainly dimethylarsenate (DMA)), arsenoribosides (glycerol, phosphate, and sulfate) and metabolites (dimethylarsenoethanol (DMAE)). Subtle differences in arsenic species distributions exist between chlorophyte and heterokontophyte species with As(V) commonly found in water-soluble cell fractions of chlorophyte species, while DMA is more common in heterokontophyte species. Additionally, different arsenoriboside species are found in each phyla with glycerol and phosphate arsenoribosides produced by chlorophytes, whereas glycerol, phosphate, and sulfate arsenoribosides are produced by heterokontophytes, which is similar to existing data for marine macro-algae. Although arsenoribosides are the major arsenic species in many marine unicellular algal species, AB has not been detected in unicellular algae which supports the hypothesis that AB is formed in marine animals via the ingestion and further metabolism of arsenoribosides. The observation of significant DMAE concentrations in some unicellular algal cultures suggests that unicellular algae-based detritus contains arsenic species that can be further metabolized to form AB in higher marine organisms. Future research establishing how environmental variability influences the production of arsenic species by marine unicellular algae and what effect this has on arsenic cycling within marine food webs is essential to clarify the role of these organisms in marine arsenic cycling.

Uptake and transformation of arsenic during the vegetative life stage of terrestrial fungi

Many species of terrestrial fungi produce fruiting bodies that contain high proportions of arsenobetaine (AB), an arsenic compound of no known toxicity. It is unknown whether fungi produce or accumulate AB from the surrounding environment. The present study targets the vegetative life stage (mycelium) of fungi, to examine the role of this stage in arsenic transformations and potential formation of AB. The mycelia of three different fungi species were cultured axenically and exposed to AB, arsenate (As(V)) and dimethylarsinoyl acetic acid for 60 days. Agaricus bisporus was additionally exposed to hypothesized precursors for AB and the exposure time to As(V) and dimethlyarsinic acid was also extended to 120 days. The mycelia of all fungi species accumulated all arsenic compounds with two species accumulating significantly more AB than other compounds. Few biotransformations were observed in these experiments indicating that it is unlikely that the mycelium of the fungus is responsible for biosynthesizing AB.