No abstract

Environmental context. Although organoarsenic compounds occur in marine organisms at high concentrations, the origin and role of these compounds is unknown. Arsenic-containing lipids (arsenolipids) are newly discovered compounds in fish. We identify a range of arsenolipids in algae and propose that algae are the origin of these unusual arsenic compounds in marine ecosystems.Abstract. Fourteen arsenolipids, including 11 new compounds, were identified and quantified in two species of brown algae, Wakame (Undaria pinnatifida) and Hijiki (Hizikia fusiformis), by high resolution mass spectrometry, high performance liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry. Both algal species contained arsenosugar-phospholipids as the major type of arsenolipid, and arsenic-hydrocarbons were also significant components, particularly in Hijiki. The origin of the various arsenolipids, and the possible significance of their relative quantities, is briefly discussed. Arsenic-containing organic compounds are abundant in marine ecosystems where they are thought to play a pivotal role in the cycling and detoxification of potentially toxic inorganic arsenic (arsenate) present in seawater. [1] Although most of the arsenic compounds identified so far have been water-soluble species, the early work on arsenic marine chemistry focussed on lipidsoluble compounds, so called arsenolipids. [2][3][4] Identification of these arsenolipids proved difficult, however, and it was not until 1988 that an arsenolipid was first rigorously characterised and identified as an arsenosugar-containing phospholipid [5] (see Table 1, compound As-PL958).Subsequently, the range of naturally occurring arsenolipids has been extended with the discovery of arsenic-containing fatty acids in fish oils, [6] and arsenic-containing hydrocarbons in fish oils, [7] fish liver, [8] sashimi tuna [9] and fish meal. [10] The origin of these compounds was presumed to be algae. We report the arsenolipid profiles of two species of brown algae, determined mainly by high performance liquid chromatography-mass spectrometry (HPLC-MS), and we briefly discuss the possible biosynthetic origin of these unusual compounds.Samples of Wakame (Undaria pinnatifida, 40 AE 3 mg As g À1 dry mass) and Hijiki (Hizikia fusiformis, 113 AE 5 mg As g À1 dry mass), A obtained from a Japanese commercial source, were extracted with a mixture of chloroform and methanol using a modification B of the classical procedure of Bligh and Dyer. [11] The lipid fraction containing 6.7 % (Wakame) and 1.6 % (Hijiki)A Determination of arsenic contents. Total arsenic analyses were performed on portions of the dry powders, extracts or combined fractions from the silica columns by ICP-MS (Agilent 7500ce) in helium collision cell mode following a microwave-assisted acid mineralisation step. The method was validated by analysis of reference material NIES No. 9 Sargasso (certified As content 115 AE 5 mg As g À1 ); we obtained 116 AE 2 mg As g À1 (n ¼ 3). BExtraction and purification of arsenolipid...

The presence of arsenic-containing carbohydrates, arsenosugars, in many seafoods raises questions of human health concerning the ingestion and metabolism of these compounds. A previous study investigating the metabolites in human urine after the ingestion of a common arsenosugar 2',3'-dihydroxypropyl 5-deoxy-5-dimethylarsinoyl-beta-d-riboside (oxo-arsenosugar) showed that the arsenic was rapidly excreted in the urine and was present as at least 12 metabolites, only three of which could be identified. In this repeat study with oxo-arsenosugar and using high-performance liquid chromatography/inductively coupled plasma mass spectrometry, we report the identification of seven arsenic metabolites, which together accounted for 88% of the total urinary arsenic collected over 61 h. The metabolites included previously reported human urinary arsenicals dimethylarsinate (DMA), oxo-dimethylarsenoethanol (oxo-DMAE), and trimethylarsine oxide, in addition to new human metabolites oxo-dimethylarsenoacetate (oxo-DMAA), thio-dimethlyarsenoacetate (thio-DMAA), thio-dimethylarsenoethanol (thio-DMAE), and the thio-arsenosugar. Cytotoxicity testing of the major metabolites DMA, oxo-DMAE, thio-DMAE, oxo-DMAA, and thio-DMAA showed that they were nontoxic even at 10 mM, except for DMA, which showed some toxic effects at 1 mM.

Ageing constitutes the most important risk factor for all major chronic ailments, including malignant, cardiovascular and neurodegenerative diseases. However, behavioural and pharmacological interventions with feasible potential to promote health upon ageing remain rare. Here we report the identification of the flavonoid 4,4′-dimethoxychalcone (DMC) as a natural compound with anti-ageing properties. External DMC administration extends the lifespan of yeast, worms and flies, decelerates senescence of human cell cultures, and protects mice from prolonged myocardial ischaemia. Concomitantly, DMC induces autophagy, which is essential for its cytoprotective effects from yeast to mice. This pro-autophagic response induces a conserved systemic change in metabolism, operates independently of TORC1 signalling and depends on specific GATA transcription factors. Notably, we identify DMC in the plant Angelica keiskei koidzumi, to which longevity- and health-promoting effects are ascribed in Asian traditional medicine. In summary, we have identified and mechanistically characterised the conserved longevity-promoting effects of a natural anti-ageing drug.

We report studies on the variability in human metabolism of an oxo-arsenosugar involving the ingestion of a chemically synthesized arsenosugar and quantitative determination of the arsenic metabolites in urine and serum by HPLC coupled with arsenic-selective mass spectrometric detection (ICPMS, inductively coupled plasma mass spectrometry). The total, four-day, urinary excretion of arsenic for six volunteers ranged widely from ca. 4-95%. The arsenic metabolites present in the urine also showed great variability: high arsenic excretion was accompanied by almost complete biotransformation of the ingested oxo-arsenosugar into a multitude of metabolites (>10), whereas the subjects that excreted low amounts of arsenic produced low quantities of metabolites relative to unchanged oxo-arsenosugar and its thio-analogue. Major arsenic urinary metabolites were dimethylarsinate (DMA) and possible intermediates in the degradation of arsenosugar to DMA, namely, dimethylarsinoylethanol (DMAE) and dimethylarsinoylacetate (DMAA) present both as their oxo- and thio-analogues. Thio-DMAE and thio-DMAA were also found in blood serum indicating that these species were formed in the liver rather than on storage of the urine in the bladder. The large variability in the way individuals metabolize arsenosugars has implications for risk assessment of arsenic intake from seafood.