Hydrophobic natural deep eutectic solvents for marine lipid extraction

‘Type V' natural deep eutectic solvents (TV NADES) are a novel class of solvent media with many potential ‘green chemistry’ applications. Here, we assess the potential of two TV NADES: menthol:carvacrol (M:C) and menthol:thymol (M:T), and a single terpenoid extraction media carvacrol (C), as media from total lipid extraction of three compositionally diverse, freeze-dried marine tissues: hoki (Macruronus novaezelandaiae), jack mackerel (Trachurus declivis) and green-lipped mussel (kuku, Perna canaliculus). Room temperature extraction yields into these media were benchmarked relative to lipid yields from chloroform-methanol-water extractions. Relative extraction yields using the M:C and M:T media were (both) 87% for jack mackerel, 85%–87% for hoki, and 43%–47% for green-lipped mussels. Comprehensive chemical analyses of TV NADES lipid extracts suggested that neutral lipids were extracted in greater yield than phospholipids, and that phosphatidylinositol, lysophospholipids and (in the case of mussels) ceramideaminoethylphosphonates were particularly resistant to extraction into C, M:C and M:T. C—a thymol isomer that, unlike menthol and thymol is a liquid at room temperature—appeared to perform (marginally) better than M:C and M:T systems, implying there may be no advantage to using the TV NADES over a single terpenoid with similar chemistry for total lipid extraction.