Free fatty acid profiling in marine algae extract by LC-MS/MS and isolation as well as quantification of the ω-3 fatty acid hexadeca-4,7,10,13-tetraenoic acid.

Undaria pinnatifida (Wakame) alga contains high amounts of hexadeca-4Z,7Z,10Z,13Z-tetraenoic acid which was reported to decrease the efficiency of cisplatin chemotherapeutics. To obtain a fatty acid enriched extract of this ω-3 poly-unsaturated fatty acid as an analytical standard, Wakame was used as source material for its extraction. A two-step extraction protocol consisting of a liquid-liquid extraction followed by solid-phase extraction with 3-aminopropyl silica in accordance to a normal-phase elution mode was developed. An ultra high performance liquid chromatography with electrospray ionization tandem mass spectrometry method based on sequential windowed acquisition of all theoretical fragment ion mass spectra allowed a simultaneous comprehensive group selective fatty acids profiling in untargeted manner and quantitative analysis of the targeted fatty acid. Hexadeca-4Z,7Z,10Z,13Z-tetraenoic acid was identified using high-resolution product ion spectra. The quantitative method was based on d5-deuterated hexadeca-4Z,7Z,10Z,13Z-tetraenoic acid which was employed as surrogate calibrant. Preliminary method validation was performed by evaluating detection and quantification limits, linear range, intra-assay and inter-day precision. Finally, a concentration of 421.2 ± 14.9 ng/mL (4% CV) of hexadeca-4Z,7Z,10Z,13Z-tetraenoic acid was determined in the extract which was further used as analytical standard.