Electrospray ionization mass spectrometry characterization of ubiquitous minor lipids and oligosaccharides in milk of the camel (Camelus dromedarius) and their inhibition of oxidative stress in human plasma

Abstract

The aim of this study was to characterize minor lipids in methanol fraction extracted from raw camel milk after loading it on a water-preconditioned short C18 open column and fractionating with a gradient of methanol/water. The C18 column showed high fractionation efficiency of minor lipids, such as glycosphingolipids, lipopolysaccharides, or oligosaccharides, when compared with other constituents, in particular polysaccharides, proteins, and free fatty acids. Liquid chromatography electrospray ionization tandem mass spectrometry in negative ion mode was used to identify 21 new glycosphingolipids, lipopolysaccharides, and oligosaccharides. Electrospray ionization tandem mass spectrometry was qualified to provide relevant data for recognizing the molecular mass, glycosylation sequences, and structure of saccharide moieties for the revealed compounds. The sequence of combinations of one selected lipopolysaccharide, which was considered the backbone of the remaining lipopolysaccharides, was confirmed in a density functional theory study. The obtained results showed that the tested fraction is a rich source of glycosphingolipids, lipopolysaccharides, and oligosaccharides with antioxidant activity.

Keywords: antioxidant; camel milk; density functional theory; glycosphingolipid; oligosaccharide.