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Arseno lipids in salmon are partly converted during cooking


Fish is considered to be an important part of healthy diet because it contains nutrients associated with beneficial health effects such as polyunsaturated fatty acids. However, fish also contribute substantially to dietary arsenic, which is considered one of the trace elements of most concern with respect to human health. A great variety of arsenic compounds have been found in fish including inorganic arsenic forms, water-soluble organoarsenicals, and lipid-soluble arsenolipids all differing in their toxicity. While inorganic arsenic species are highly toxic, their concentration in fish is generally too low for creating a health hazard. On the other side the high concentration of water-soluble arsenic species, often mainly present as arsenobetaine, are considered harmless. Unfortunately, the same low toxicity has not been observed for the arsenolipids. Especially, one group of arsenolipids, the arsenic-containing hydrocarbons has cytotoxicity comparable to that of inorganic arsenic. Because of such toxicity, risk assessments of arsenolipids in seafood have been performed. Yet such evaluation has focused on raw products, and the effect of food preparation such as cooking or frying has not been assessed for these compounds.

The new study:
To close such gap, an international group of researchers investigated the changes taking place to arsenolipids during either baking or steaming salmon. Speciation analysis has been performed by using HPLC coupled with both inductively coupled plasma mass spectrometry (ICP-MS) and electrospray mass spectrometry (ESMS) to determine the arsenic species before and after cooking.

Salmon fish fillets were either cooked by baking in the oven at 200°C for 15 min., or by steaming at 100°C for 5 min. Both cooked and raw fish fillets were frozen at -80 °C and then freeze dried to constant dry mass. A portion of the dried fish powder was then extracted with hexane, the hexane was evaporated and the oily residue was extracted with ethanol. The remaining fish pellet was then extracted with water. Both the ethanol and water extracts were then analyzed by HPLC with mass spectrometric detection, using reversed-phase HPLC-ICP-MS/ESMS for the ethanol extracts and a cation exchange HPLC-ICP-MS for the aqueous extracts.

Figure:  Chemical structure of
1-(dimethylarsinyl)pentadecane (oxo-AsHC 332)  
and 1-(dimethylarsinyl-sulfanidyl)pentadecane
(thioxo-AsHC 348).

The speciation analysis revealed that about 6% of the total arsenic was lipid-soluble, consisting of three arsenic hydrocarbons (oxo-AsHC 332, oxo-AsHC 360, and oxo-AsHC 405, together 55% of the arsenolipid fraction) and a band of unidentified less-polar arsenolipids (ca 40%) together with trace amounts of 6 other species. The comparison between raw and cooked fish fillets revealed that about 28% of the oxo-AsHC were converted to their thioxo analogs.

The authors concluded that the greater lipophilicity of the thioxo analogs could alter the mode of toxicity of the arsenic hydrocarbons which should be considered in future regulations related to food safety.

The original publication

Chan Xiong, Ronald A. Glabonjat, Md Hasan Al Amin, Michael Stiboller, Jun Yoshinaga, Kevin A. Francesconi, Arsenolipids in salmon are partly converted to thioxo analogs during cooking, J. Trace Elem. Med. Biol., 69 (2022) 126892. DOI: 10.1016/j.jtemb.2021.126892

Instrumentation used:

Agilent Technologies Inc., 7900 ICP-MS
Agilent Technologies Inc.,  1260 HPLC
Agilent Technologies Inc., 6460 Triple Quadrupole LC/MS
Dionex Ultimate 3000 HPLC
Thermo Scientific Q-Exactive Orbitrap

Related studies (newest first)

F. Ebert, V. Ziemann, V.K. Wandt, B. Witt, S.M. Müller, N. Guttenberger, E.E. Bankoglu, H. Stopper, G. Raber, K.A. Francesconi, T. Schwerdtle, Cellular toxicological characterization of a thioxolated arsenic-containing hydrocarbon, J. Trace Elem. Med. Boil. Org. Soc. Miner. Trace Elem. (GMS) 61 (2020), 126563. DOI: 10.1016/j.jtemb.2020.126563

M. Stiboller, F.P. Freitas, K.A. Francesconi, T. Schwerdtle, A.J.A. Nogueira, G. Raber, Lipid-soluble arsenic species identified in the brain of the marine fish skipjack tuna (Katsuwonus pelamis) using a sequential extraction and HPLC/mass spectrometry, J. Anal. At. Spectrom. 34 (2019) 2440–2450. DOI: 10.1039/c9ja00249a

B. Witt, S. Meyer, F. Ebert, K.A. Francesconi, T. Schwerdtle, Toxicity of two classes of arsenolipids and their water-soluble metabolites in human differentiated neurons, Arch. Toxicol. 91 (2017) 3121–3134. DOI: 10.1007/s00204-017-1933-x

B. Witt, F. Ebert, S. Meyer, K.A. Francesconi, T. Schwerdtle, Assessing neurodevelopmental effects of arsenolipids in pre-differentiated human neurons, Mol. Nutr. Food Res. 61 (2017) 1700199. DOI: 10.1002/mnfr.201700199

A.-C. Niehoff, J. Schulz, J. Soltwisch, S. Meyer, H. Kettling, M. Sperling, A. Jeibmann, K. Dreisewerd, K.A. Francesconi, T. Schwerdtle, U. Karst, Imaging by elemental and molecular mass spectrometry reveals the uptake of an Arsenolipid in the brain of Drosophila melanogaster, Anal. Chem. 88 (2016) 5258–5263. DOI: 10.1021/acs.analchem.6b00333

S. Meyer, M. Matissek, S.M. Müller, M.S. Taleshi, F. Ebert, K.A. Francesconi, T. Schwerdtle, In vitro toxicological characterisation of three arsenic-containing hydrocarbons, Metallomics,  6 (2014) 1023–1033. DOI: 10.1039/c4mt00061g

K.A. Francesconi, Arsenic species in seafood: origin and human health implications, Pure Appl. Chem. 82 (2010) 373–381. DOI: 10.1351/PAC-CON-09-07-01

V. Devesa, D. Velez, R. Montoro, Effect of thermal treatments on arsenic species contents in food, Food Chem. Toxicol. 46 (2008) 1–8. DOI: 10.1016/j.fct.2007.08.021

V. Devesa, M.A. Súńer, S. Algora, D. Vélez, R. Montoro, M. Jalón, I. Urieta, M.L. Macho, Organoarsenical Species Contents in Cooked Seafood, J. Agri. Food Chem., 53/22 (2005) 8813-8819. DOI: 10.1021/jf050499m

V. Devesa, A. Martinez, M.A. Súńer, V. Benito, D. Vélez, R. Montoro, Kinetic study of transformations of arsenic species during heat treatment, J. Agri. Food Chem., 49 (2001) 2267-2271. DOI: 10.1021/jf001328e

Vicenta Devesa, Mari Luz Macho, Mercedes Jalón, Inés Urieta, Ociel Muńoz, María Angeles Súńer, Fernando López, Dinoraz Vélez, Rosa Montoro, Arsenic in Cooked Seafood Products: Study on the Effect of Cooking on Total and Inorganic Arsenic Contents, J. Agri. Food Chem., 49 (2001) 4132-4140. DOI: 10.1021/jf010274l

V. Devesa, A. Martínez, M.A. Súńer, D. Vélez, C. Almela, R. Montoro, Effect of Cooking Temperatures on Chemical Changes in Species of Organic Arsenic in Seafood, J. Agri. Food Chem., 49/5 (2001) 2272-2276. DOI: 10.1021/jf0013297

K. Hanaoka, W. Goessler, H. Ohno, K.-J. Irgolic, T. Kaise, Formation of toxic arsenical in roasted muscles of marine animals, Appl. Organomet. Chem., 15/1 (2001) 61-66. DOI: 10.1002/1099-0739(200101)15:1<61::AID-AOC70>3.0.CO;2-2

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last time modified: December 12, 2021


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