Nonulosaminic acid

Zilliken, F., and Whitehouse, M. W., The Nonulosaminic Acids—Neuraminic Acids and Related Compounds (Sialic Acids), 13, 237-263 Zorbach, W. Werner, and Bhat, K. Venkatramana, Synthetic Carde-nolides, 21, 273-321... 

This section deals with acids, that are formally modified aldonic acids, such as keto, deoxy, and branched-chain acids (including the so-called saccharinic acids). The aminoaldonic acids, which are oxidation products of amino sugars, and, in particular, the important nonulosaminic acids (neuraminic acids) and muramic acid, are not discussed here. The formation of saccharinic acids by the treatment of sugars with alkali, and the mechanisms involved, are likewise outside the scope of this chapter. 

The second pathway for the formation of 3-deoxyulosonic acids is, at present, represented only by the condensation of pyruvate with iV -acetyl-n-mannosamine to form a nonulosaminic acid (iV-acetylneuraminic acid). - This reaction is readily reversible, but the point of equilibrium is 90 per cent toward degradation and 10 per cent toward synthesis of the iV-acetyl-neuraminic acid. ... 

More complicated compounds related to monosaccharides are also implicated in the formation of certain polysaccharides. Acid esters, acids derived from deoxysugars, aminosugars, N-acetylated aminosugars, sialic acids (nonulosaminic acids which are N-or O- substituted derivatives of neuraminic acid), etc., are not uncommon as... 

THE NONULOSAMINIC ACIDS Neuraminic Acids and Related Compounds (Sialic Acids)... 

Relationship of the Various Nonulosaminic Acids to Neuraminic Acid... 

In the literature, there has been much confusion concerning the nomenclature of these nonulosaminic acids. Thus, the name neuraminic add was first given to the monomethoxy compound, isolated after the methanolysis of gangliosides, and was then subsequently transferred to the methoxyl-free, parent acidP It should here be noted that neuraminic acid has not been isolated and characterized as such. 

The name sialic acid" has been given to the several nonulosaminic acids isolated from the submaxillary mucoproteins, although the chemical composition of these varies with the species source. Svennerholm has proposed that the name sialic acid be restricted to the basic structure common to all these various sialic acids thus ovine sialic acid" would be designated Af-acetylsialic acid. However since this basal component, here termed sialic acid, is identical with neuraminic acid, it would seem more appropriate to adopt the name neuraminic acid for the parent add and to retain the name sialic acid to denote the various mono- and di-acyl neuraminic acids of natural occurrence in mucoproteins, regardless of their source. This is the convention which has been used in referring to the various nonulosaminic acids in Table I and thoughout this article. ... 

The acids are also constituents of certain oligosaccharides in milk. A dialyzable form of a nonulosaminic acid has been detected in cerebrospinal fluid i this compound may be such an oligosaccharide. 

It is perhaps worth noting that D-galactose has been found in all those mucosubstances and oligosaccharides of animal origin which contain nonulosaminic acids. 

Nonulosaminic acids are found as constituents of certain water-soluble, lipid fractions (glycolipids) of animal tissues, being particularly associated with gangliosides as well as with more complex lipopolysaccharides. The detection and characterization of the nonulosaminic acid component in these mucolipids has been based upon one or more of the color reactions (see below) applied to the macromolecular material, followed by isolation therefrom of methoxyneuraminic acid after methanolysis. The question of whether or not one or more acylated forms of neuraminic acid are actually present in the mucolipid has still to be resolved. Svennerholm has reported the isolation of A-acetylneuraminic acid from brain gangliosides. 

In some, if not all of these sialoproteins, the nature of the nonulosaminic acid appears to vary with the species. The mucin extracted from sub-maxillary glands is a common source for isolation of the acids. Human saliva affords IV-acetylneuraminic acid, which is also present in human milk, human-brain gangliosides, and human-serum proteins. 

Analysis of the component serum albumins and globulins indicates that nonulosaminic acids are associated only with the globulin fractions, - the Qii-acid glycoprotein (orosomucoid) having the highest content (10%). The low isoelectric point of this sialoprotein is attributable to the nonulosaminic acid content. - In pathological states in humans, the values for nonulosaminic acid in the serum are significantly increased - - from a normal value of about 65 mg. per 100 ml. In other animals, the... 

Milk contains a number of oligosaccharides, including some which contain a nonulosaminic acid glycosidically hnked. These are discussed... 

Qualitatively, the presence of the nonulosaminic acids is best indicated by the brilliant-red coloration formed on addition of an acidic solution of p-dimethylaminobenzaldehyde (the so-called direct Ehrlich reaction ), and by the bright-purple coloration which develops upon boiling with Bial s reagent for several minutes at 100°. In addition, the nonulosaminic acids give a blue-violet coloration with Dische s diphenylamine reagent for deoxypentoses and a positive reaction in the tryptophan-perchloric acid test. Since no single one of these color reactions is absolutely specific for a nonulosaminic acid, it is advisable to carry out at least two of these for a qualitative analysis. For quantitative determinations, all four reactions have been employed, using either A/ -acetylneuraminic acid (m. p., 183-185° [a] —32.0°) or methoxyneuraminic acid [m. p., 200° (dec.) [a]o —55.0°] as colorimetric standards. 

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