Investigating challenges in handling, stability and recovery of prymnesins

Prymnesium parvum is a globally distributed haptophyte that produces an array of ichthyotoxic compounds known as prymnesins. Prymnesins are large polyethers ranging in size from 1600 to 2300 Da. Initial investigations towards the development of prymnesin reference materials identified significant problems with recovery and stability. A systematic series of studies was conducted to determine the effects of solvent composition, pH, evaporation to dryness and solid-phase extraction (SPE) resin on the stability and recovery of prymnesins. Experiments investigated A- and B-type prymnesins to verify whether the observed behaviours were type specific. The results indicated significant effects on prymnesin stability, solubility and recovery depending on the conditions used. Prymnesins were soluble and stable in solvents containing a minimum of 70% organic solvent (methanol) under mildly acidic to weakly basic pH. Additionally, prymnesins were insoluble in acetonitrile and formed imine derivatives in acetone. Prymnesins were unstable when stored dry, with time-dependent losses observed. Lastly, SPE resin type and protocol design had a significant impact on prymnesin recovery. These findings, highlighting the multiple factors affecting prymnesin recovery, will improve extraction procedures and isolation yields, and should be considered when performing prymnesin toxicological or bioactivity research.