31P NMR quantification and monophasic solvent purification of human and bovine lens phospholipids

Most lipid extraction procedures [Folch, J., Lees, M., and Sloane-Stanley, G.H. (1957) A Simple Method for the Isolation and Purification of Total Lipids from Animal Tissues, J. Biol. Chem. 226, 497-509; Bligh, E.G., and Dyer, W.J. (1959) A Rapid Method of Total Lipid Extraction and Purification, Can. J. Biochem. Physiol. 37, 911-917] employ biphasic solvent mixtures designed to dissolve the lipids in an organic phase and remove impurities in an aqueous phase. However, when applying these protocols to biological matrices such as that of the ocular lens, the formation of an emulsion layer between the organic and aqueous phases causes poor reproducibility in extraction yields and gives only a small amount of the lipid-containing chloroform phase. In this study, we quantified phospholipids at each step of the Folch et al. extraction protocol and compared the yield of human and bovine lens phospholipids obtained by the Folch-based approach and a novel monophasic methanol extraction method designed to circumvent the problems associated with biphasic extraction protocols. A monophasic methanol extraction coupled with 31P NMR spectroscopy was found to be the simplest, quickest, and most effective method for quantifying the phospholipid content of the lens.