Rapid complexing of oxoacylglycerols with amino acids, peptides and aminophospholipids

We prepared model Schiff bases from 2-[9-oxo]nonanoyl glycerol (2-MAG-ALD) and various amino compounds. 2-MAG-ALD was obtained by pancreatic lipase hy drolysis of trioleoyl glycerol and reductive ozonolysis of the resulting 2- monooleoyl glycerol. The reaction products were purified by thin-layer chro matography. Schiff bases were synthesized in greater than 50% yield by reac ting 2-MAG-ALD with twofold molar excess of valine, N alpha-acetyl-L-lysine methyl eater and the tripeptides glycyl-glycyl-glycine, glycyl-glycyl-hist idine, and glycyl-histidyl-lysine in aqueous methanol and with 1-palmitoyl- 2-stearoyl glycerophosphoethanolamine (PE) in chloroform/methanol for 16 h at room temperature. Prior to analysis the bases were reduced with sodium c yanoborohydride in methanol for 30 min at 4 degrees C. Reaction products we re analyzed by high-performance liquid chromatography/electrospray ionizati on/mass spectrometry (HPLC/ESI/MS). Reduced Schiff bases of 2-MAG-ALD with PE and amino acids were analyzed by normal-phase HPLC/ESI/MS and those with peptides by reversed-phase HPLC/ESI/MS. Single adducts were obtained in al l cases and both the alpha-amino group of valine and the E-amino group of N alpha-acetyl-L-lysine methyl ester were reactive. Molecular ions of reacti on products were the only detected ions in the negative ionization mode, wh ereas in the positive ion mode sodiated molecular ions were also detected. The present study suggests that 2-MAG-ALD may form Schiff base adducts with amino compounds in other aqueous media, such as the intestinal lumen and i n the hydrophobic environment of cell membranes.