Abstract
Seaweeds contain large amounts of organoarsenic compounds, mostly arsenosugars (AsSug) and arsenolipids (AsLipid). AsSug is mainly metabolized into dimethylarsinic acid (DMAV) in humans. However, this metabolic process is not well understood. We investigated the metabolism of an AsSug, 3-[5'-deoxy-5'-(dimethylarsinoyl)-β-ribofuranosyloxy]-2-hydroxypropylene glycol (AsSug328), in the gastrointestinal tract using an in vitro artificial gastrointestinal digestion system. AsSug328 was incubated with gastric juice for 4 h, with bile-pancreatic juice for 0.5 h, and finally with enteric bacteria solution for 24 h. The conversion of arsenic compounds after artificial digestion was analyzed by HPLC-ICP-MS and HPLC-ESI-Q-TOF-MS. Our results show that artificial gastrointestinal digestion converted AsSug328 into thio-AsSug328. However, no formation of DMAV was detected. Under the artificial digestion system, the 5-deoxyribofuranose structure of AsSug was maintained. Therefore, AsSug should be absorbed in the intestinal tract after its sugar moiety is partially decomposed. They are then possibly metabolized to DMAV in the liver and subsequently excreted through urine.
Highlights
Seafood is known to be abundant in arsenic compounds [1, 2, 3]
The International Agency for Research on Cancer (IARC) has placed arsenic and inorganic arsenic in Group 1, and monomethylarsonic acid (MMAV) and dimethylarsinic acid (DMAV) in Group 2B [10]
We investigated the degradation of AsSug328, in vitro, using artificial digestive juices consisting of gastric juice, bile-pancreatic juice, and intestinal bacterial flora obtained from a healthy adult human
Summary
Most of which are arsenosugars (AsSugs) and arsenolipids (AsLipids) [4, 5, 6, 7, 8, 9]. IARC has not assessed the carcinogenicity of AsSug and AsLipid because of the lack of information about their metabolism and intermediates formed. AsSugs were reported to be metabolized into dimethylated arsenic compounds, such as DMAV, thiodimethylarsenoethanol (thio-DMAEV), and thio-dimethylarsenoacetic acid (thio-DMAAV), for excretion into the human urine [11, 12, 13]. A noteworthy fact is that dimethylmonothioarsinic acid (DMMTAV) is a trace arsenical that is excreted in human urine after ingestion of AsSug [12]. DMMTAV is as genotoxic and cytotoxic as dimethylarsinous acid (DMAIII), which is a known carcinogen [14]. It is necessary to clarify the processes for the degradation of AsSug into DMAV in the digestive system
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