Arsenic compounds marine algae

Marine algae transform arsenate into nonvolatile methylated arsenic compounds such as methanearsonic and dimethylarsinic acids (Tamaki and Frankenberger 1992). Freshwater algae and macrophytes, like marine algae, synthesize lipid-soluble arsenic compounds and do not produce volatile methylarsines. Terrestrial plants preferentially accumulate arsenate over arsenite by a factor of about 4. Phosphate inhibits arsenate uptake by plants, but not the reverse. The mode of toxicity of arsenate in plants is to partially block protein synthesis and interfere with protein phosphorylation — a process that is prevented by phosphate (Tamaki and Frankenberger 1992). 

Arsenic-Containing Compounds from Marine Algae... 

Aridreae, M. O., and Klumpp, D. (1979). Biosynthesis and release of organo-arsenic compounds by marine algae. Environ. Sci. Technol. 13, 738-741. 

Cullen, W.R., Harrison, L.G., Li, H. and Hewitt, G. (1994) Bioaccumulation and excretion of arsenic compounds by a marine unicellular alga, Polyphsa peniculus. Appl. Otganomet. Chem., 8, 313—324. 

The marine environment is a vast resource for the discovery of structurally unique bioactive secondary metabolites, some belonging to totally novel chemical classes.8 Sessile benthic organisms including the Porifera, Cnidaria, Bryozoa, and Tunicata as well as marine algae have developed an arsenal of compounds which have been demonstrated to confer a competitive advantage in ecosystems characterized by extreme resource limitations. Interactions of these organisms at the genetic,... 

T. Raise, Y. Oya-Ohta, T. Ochi, T. Okubo, R. Hanaoka, R. J. Irgolic, T. Sakurai, C. Matsubara, Toxicological study of organic arsenic compound in marine algae using mammalian cell culture techniques, J. Food Hyg. Soc. Jap., 37 (1996), 135-141. 

Bacterial demethylation of methylarsenicals is known to occur in aerobic aqueous and terrestrial environments, giving rise to CO2 and arsenate. Common soil bacteria, such as Mycobacterium, Alcaligenes, and Pseudomonas, are known to demethylate mono- and dimethylarsenic compounds. An important part of the biogeological cycling of arsenic involves bacterial demethylation of methylarsenic acids excreted by marine algae, although the mechanism(s) of demethylation of methylated arsenic compounds is essentially unknown. 

Although arsenobetaine was first reported as the natural major arsenical in marine animals almost 30 years ago, there is still no clear biosynthetic scheme for this compound. An early proposal was that oxo-arsenosugars were the likely precursors based on several observations. First, oxo-arsenosugars are abundant in marine algae and they occur together with arsenobetaine in animals that feed on algae. Second, laboratory experiments simulating environmental conditions produced oxo-DMAE, which appealed as a possible intermediate in the formation of arsenobetaine... 

Arsenosugars are the major arsenic compounds in marine algae. They chiefly comprise water-soluble dimethylarsinoyl compounds (see Fig. 2, compounds 1-4 and 6-11), although lipid-soluble derivatives (see Fig. 2, compound 5) and quaternary arsonio analogues (see Fig. 2, compounds 12-14) are also found (4). Although many arsenosugars have been identified in algae, there are only four (see Fig. 2, compounds 1-4) that are commonly found. 

Marine algae also contain a considerable amount (up to 50%) of lipid-soluble arsenic (39). This arsenic has been rigorously identified on only one occasion, and shown to be a phospholipid derivative (see Fig. 2, compound 5) of an arsenosugar (82,83). 

Table 2 Arsenic Compounds in Marine Algae and Plants ... 

Freshwater algae have been little studied compared with their marine counterparts, but their pattern of arsenic compounds appears to be similar (15,70). Arse-nosugars are present as major or significant compounds (only compounds 1 and 2 in Fig. 2 have been reported so far). Arsenate can also be a major arsenical in freshwater algae, and small amounts of dimethylarsinate and methylarsonate have also been reported. Arsenite has not been detected. 

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