Organoarsenic Chemistry - in Nature

In Nature

As arsenic is toxic to most life forms and it occurs in elevated concentration in some areas several detoxification strategies have evolved. Inorganic arsenic and its compounds, upon entering the food chain, are progressively metabolized to a less toxic form of arsenic through a process of methylation. Organoarsenic compounds arise via biomethylation of inorganic arsenic compounds, via processes mediated by enzymes related to vitamin B₁₂. For example the mold Scopulariopsis brevicaulis produce significant amounts of trimethylarsine if inorganic arsenic is present. The organic compound arsenobetaine, a betaine, is found in some marine foods such as fish and algae, and also in mushrooms in larger concentrations. The average person's intake is about 10-50 µg/day. Values about 1000 µg are not unusual following consumption of fish or mushrooms. But there is little danger in eating fish because this arsenic compound is nearly non-toxic. Arsenobetaine was first identified in the Western rock lobster

Carbohydrates bound to arsenic, collectively known as arsenosugars, are found especially in seaweeds. Arsenic containing lipids are also known. Although arsenic and its compounds are toxic for humans, one of the first synthetic antibiotics was Salvarsan (the use of which has long been discontinued).

The only polyarsenic compound isolated from a natural source is arsenicin A.

Organoarsenic compounds may pose significant health hazards, depending extremely on their speciation (LD₅₀ ranging from 5–6 mg /kg bw (very toxic) to 12000–15000 mg / kg bw (practically non-toxic).