Distribution of arsenic species by seaweed parts, especially arsenic lipids




Rebecca Sim, Ásta H. Pétursdóttir, Natasa Desnica, Jörg Feldmann, Guðmundur Haraldsson, Karl Gunnarsson, Liberty O'Brien, Marta Weyer and Hildur I. Sveinsdóttir.

Supported by:

Icelandic Research Fund


Rebecca Sim

Ph.D. Student

Distribution of arsenic species within the macroalgae 
– an emphasis on arsenolipids

Algae are rich in minerals and desirable bioactive substances, but they can also absorb large amounts of trace elements, such as toxic heavy metals, including the element arsenic. Arsenic is found as inorganic arsenic in the sea and is taken up in that chemical form by the algae. In the algae, however, arsenic is detected not only as inorganic arsenic but as a wide range of arsenic compounds, so-called organic compounds of arsenic, for example arsenosaccharides and arsenolipids. There is still a lot of mystery about the origin of these compounds. In general, organic forms of arsenic have been considered quite harmless, unlike inorganic arsenic, which is a known carcinogen. However, recent studies on arsenolipids have shown that they can be as cytotoxic as inorganic arsenic. It is also believed that arsenosugar can possibly have long-term negative effects with regular consumption. Levels of arsenolipids are generally not high in algae, but the starting point of their production is thought to occur in algae. Algae are part of the regular food intake in the Eastern part of the world and are becoming increasingly popular in the West, so more information about these compounds is urgently needed to fully assess the risks associated with their consumption as well as to ensure that appropriate regulations are put in place regarding their maximum levels in foodstuffs. In order to understand the toxicological effects of algae consumption, it is extremely important that more data be collected on all the different chemical forms of arsenic, in particular on arsenolipids, but limited information is currently available on them. Samples of red, green and brown algae were collected near Grindavík and Kjalarnes, at two different points in time. The samples were thoroughly analyzed for heavy metals and arsenic analysis was carried out to better understand the chemical form in which the arsenic was present. Selected samples of brown, red and green algae were measured for species analysis of arsenolipids using mass spectrometry HPLC-ICP-M/ESI-MS/MS and HPLC-qToF-MS. In addition, brown macroalgae were divided into biological fractions to determine whether the distribution of arsenic species is uniform throughout the seaweed. Limited information exists globally on arsenolipids in seaweed, so this extensive profiling of them in different species of algae will help elucidate how these enigmatic organic compounds are formed and where they are stored. The data can also be used for risk assessment of arsenic species in seaweed for human consumption and can therefore influence future food safety legislation.
In recent years seaweed has gained popularity as a health food due to its high content of minerals and vitamins. However, seaweeds may also accumulate high levels of potentially toxic elements – in particular arsenic, which may become incorporated into larger biological molecules such as sugars and lipids. It is unclear how these organic arsenic compounds are formed/stored and if they may serve a biological purpose (ie, detoxification or energy storage). However, toxicological studies into arsenic-containing lipids have demonstrated cytotoxicity comparable to that of arsenite, a known carcinogen, and arsenic-containing sugars are suspected to display toxicity with chronic exposure. This project aims to investigate variations in the distribution of arsenic compounds throughout several classes and species of seaweed. Samples of brown, red and green macroalgae were collected from two locations in Iceland across two different months and analyzed for several potentially toxic elements as well as hydrophilic arsenic speciation using HPLC-ICP-MS. Brown macroalgae were additionally sectioned into anatomical parts to determine if the distribution of arsenic species differs throughout the thallus. Select samples were chosen for state-of-the-art lipophilic arsenic speciation using HPLC-ICP-MS/ESI-MS/MS and HPLC-qToF-MS. Limited information is available on arsenic speciation in seaweed thus it is hoped that this extensive profiling of several different species will help elucidate how these unusual compounds are formed and stored. The data from this project will also contribute to the necessary information needed for the risk assessment of arsenic species in seaweed for human consumption and may have an impact on future food safety legislation.

View report