Isolation and purification of arsenolipids from natural marine sources for use in speciation and toxicological studies

Abstract

Environmental context Arsenic exists in different chemical forms in our environment, among others as arsenolipids that are predominately found in appreciable quantities in various marine organisms (seafood). Their origin, biosynthetic pathway, toxicity and their potential biological role are not fully understood. We report purification strategies for environmental and human health relevant arsenolipids to broaden and support innovative arsenolipid research.Rational This study aims to isolate and purify common arsenolipids found in various seafood from commercially available marine sources to provide an alternative approach to the challenging chemical synthesis.Methodology Arsenic containing fatty acids and arsenic containing hydrocarbons were purified from salmon oil, and the edible dried seaweed Wakame was used for the purification of di-acyl arsenosugar phospholipids and arsenic containing hydrocarbons. The developed purification protocols apply and combine straightforward analytical techniques by means of chemical hydrolysis, solid–liquid extraction, solvent-partitioning, solid-phase extraction and preparative liquid chromatography. Elemental mass spectrometry and HPLC/mass spectrometry were used for the development of the purification protocols and the characterisation of purified natural extracts of arsenolipids.Results The salmon oil (20.0 kg) and Wakame (0.50 kg) samples contained 12.8 and 3.19 mg of lipid-soluble arsenic, respectively. The final purified extracts of arsenic fatty acids and arsenic hydrocarbons obtained from salmon oil contained 0.52 mg As in 85 mg of total mass and 2.19 mg As in 28 mg of total mass, respectively. Purification of di-acyl arsenosugar phospholipids and arsenic containing hydrocarbons from Wakame returned extracts containing 0.345 and 0.237 mg As in ≤20 mg of total mass, respectively.Discussion In a natural product approach, arsenic containing fatty acids, arsenic containing hydrocarbons and di-acyl arsenosugar phospholipids have been purified in a multi-stage process from fish oil and algae samples. In the final purified extracts, around 90% or more of the arsenic was present as mixtures of arsenolipids of their respective arsenolipid classes in only minute amounts of total mass. Application of the purified mixtures in toxicological and speciation studies will benefit the future investigation of arsenolipids.