PREPARATION OF SCHIFF-BASE ADDUCTS OF PHOSPHATIDYLCHOLINE CORE ALDEHYDES AND AMINOPHOSPHOLIPIDS, AMINO-ACIDS, AND MYOGLOBIN

We have prepared Schiff base adducts of the core aldehydes of phosphat idylcholine and aminophospholipids, free amino acids, and myoglobin. T he Schiff bases of the ethanolamine and serine glycerophospholipids we re obtained by reacting (stearoyl)-2-[9-oxo]nonanoyl-glycerophosphocho line (PC-Ald) with a twofold excess of the aminophospholipid in chloro form/methanol 2:1 (vol/vol) for 18 h at room temperature. The Schiff b ases of the amino acids and myoglobin were obtained by reacting the al dehyde with an excess of isoleucine, valine, lysine, methyl ester lysi ne and myoglobin in aqueous methanol for 18 h at room temperature. Pri or to isolation, the Schiff bases were reduced with sodium cyanoborohy dride in methanol for 30 min at 4 degrees C. The reaction products wer e characterized by normal-phase high-performance liquid chromatography and on-line mass spectrometry with electrospray ionization. The amino acids and aminophospholipids yielded single adducts. A double adduct was obtained for myoglobin, which theoretically could have accepted up to 23 PC-Ald groups. The yields of the products ranged from 12 to 44% for the aminophospholipids and from 15-57% for the amino acids, while the Schiff base of the myoglobin was estimated at 5% level. The new c ompounds are used as reference standards for the detection of high mol ecular weight Schiff bases in lipid extracts of natural products.