Characterization of Arsenic Biotransformation Products from an Open Anaerobic Degradation of Fucus distichus by Hydride Generation Gas Chromatography Atomic Absorption Spectrometry and High Performance Liquid Chromatography Inductively Coupled Plasma Mass Spectrometry
This work reports on the isolation and determination of biotransformation products obtained from the organoarsenic compounds that are present in Fucus distichus when it was subjected to an open anaerobic decomposition by using the Hydride Generation Gas Chromatography Atomic Absorption Spectrometry (HG-GC-AAS) and High Performance Liquid Chromatography Inductively Coupled Plasma Mass Spectrometry (HPLC-ICP-MS). The seaweed and filtrate residues obtained from the open anaerobic degradation procedure were extracted in methanol and partitioned in phenol-ether-water mixtures to obtain water soluble extracts. The water soluble extracts were cleaned up and separated on a gel permeation Sephadex G15 column. Arsenic species concentrations were determined by using HG-GC-AAS. Final characterization of the biotransformation isolates was carried out on HPLC-ICP-MS. Only two arsenic species, 2-dimethylarsinoyl ethanol (DMAE) and dimethylarsinic acid (DMAA), were positively identified in the water soluble extract of the marine brown algae. The two arsenic species are strong intermediate candidates in the biosynthesis of arsenobetaine from oceanic arsenate in marine food webs. 1. Introduction Several species of arsenicals have been characterized in the marine environment, particularly in marine algae and seaweed which are known to concentrate high arsenic contents [1–3]. Some marine macroalgae may contain an appreciable quantity of inorganic arsenic as found in edible seaweed containing up to 50% of arsenic in the inorganic form [4]. In many studies, however, organic arsenic compounds called arsenosugars are found to be the most predominant arsenicals found in the marine macroalgae [5]. Even though marine macroalgae are at the bottom of the food chain and contain the greatest concentrations of arsenic, evidence revealed that arsenic is not biomagnified by higher organisms in the food chain [6]. Instead of biomagnifications of arsenic as one ascends the trophic levels, only accumulation and or elimination of arsenic occur in marine organism [7]. These arsenicals can be subjected to various biotransformations including reduction, oxidation, and methylation [5]. In the marine environment, biological transformation of arsenic can occur due to either microbial activities or the organism’s adaptive response to accumulated arsenic [7, 8]. The microbial transformations of arsenic can occur via redox transformation between arsenite (AsIII) and arsenate (AsV), as well as through biomethylation of arsenic into volatile methyl arsines. The primary producers, including
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