The characterization of arsenosugars in commercially available algal products including aNostoc species of terrestrial origin

The arsenic species present in a range of commercially available dried-algal food products were characterized by HPLC–ICP–MS. The products of marine origin contain up to four dimethylarsinylribosides (1) in the 8–49 ppm range and some also contain dimethylarsinic acid (DMAA). These species are easily extracted and account for most of the arsenic burden. One sample of a freshwater alga Nostoc sp. was found to contain a lower concentration of arsenic, 3 ppm, and only 34% of this was extractable. The extract representing 1 ppm of arsenic contained one of the arsenosugars 1 found in the marine samples (93%), the rest being DMAA. This is the first report of the identification of an arsenosugar from an organism of terrestrial origin. The implications of this result in connection with the global arsenic cycle are discussed.