Seven individual glycolipids (I -VII) have been isolated from the lipid extract of human saliva. All glycolipids contained glucose, glyceryl ethers and fatty acids, and differed from each other primarily with respect to the number of glucose residues. In addition, glycolipid V contained also the sulfate ester group. The structures of these glycolipids were identified by partial acid and alkaline hydrolysis, oxidation with periodate and chromium trioxide and methylation studies, as :. Diglyceride portion of these compounds consists of 1 -O-alkyl-2-O-acyl-glycerol with the docosanoate and glyceryl-monodocosyl being the predominant acyl and alkyl components.The oral, bronchial, pulmonary, gastrointestinal and reproductive tracts of higher animals secrete viscous mucus which functions mainly as lubricant and protective agent. The viscous properties of the mucous secretions are the result of the presence of high molecular weight glycoproteins called mucins. Until now, it was assumed that both mucous glycoproteins and glycolipids are similar to, or possibly derived from, those found on the cell surfaces [l]. Studies on glycolipids of the salivary glands [2,3] and the mucosa of the gastrointestinal tract [4 -91 indicate that these compounds are of glycosphingolipid nature. Our recent investigations on glycolipids of the human gastric secretion [ 10 -131 showed that these substances are composed of monoalkyl-monoacyl-glycerol and variable number of glucose residues.Since glycoproteins of the saliva and gastric secretion bear considerable structural and immunological similarities [14, 151, it was interesting to learn if the glycolipids of the saliva resemble those of the gastric secretion. Here, we describe the isolation and characterization of the glycolipids present in the human saliva.
EXPERIMENTAL PROCEDURE
MaterialsSaliva was collected from the laboratory personnel into the glass beaker placed in ice bath. Prior to collection the oral cavity of each individual involved was thoroughly rinsed with water. During sampling, care was taken to avoid the obvious contamination of saliva with nasal and bronchial secretions. The saliva was subsequently stored at -20 "C and thawed out immediately before use. Alkyl-1 -chlorides were obtained from the authentic glyceryl ethers by BCl, treatment [ 161. Alkoxyacetaldehydes were prepared from glyceryl-1 -0-alkyl standards by oxidation with periodate [I I]. Methyl ethers of glucose were from the same source as reported [ 171 and were also prepared by methylation of lactose, glucose 6-sulfate and gentiobiose [I 81. Glycosylceramides were prepared from hog gastric mucosa [19] and glyceroglucolipids from human gastric secretion [ 12,131.
A new sulfated glycolipid has been isolated from the lipid extract of human gastric content by the procedure involving column fractionation on silicic acid and thin-layer chromatography. Degradation studies revealed the presence of glucose, sulfate, fatty acids and glyceryl monoethers. The structure of this glycolipid was identified by partial acid hydrolysis, oxidation with periodate and chromium trioxide, and permethylation studies, as :
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