Methodological features of the verification of gangliosides and sialidases as potential targets of pharmacological agents

Glycosphingolipids chemically linked to sialic acids play an important role as structural scaffold molecules of the outer membranes of nerve cells in humans and animals. Progress in research on gangliosides and sialidases (i.e., enzymes involved in ganglioside hydrolysis) may make a substantial contribution to the development of promising pharmacological agents for various fields of medicine. This article presents a review of methods used both previously and at present for the qualitative and quantitative analysis of various types of gangliosides in biological samples, as well as of the activity of sialidases that degrade them. Russian and international scientific data was analyzed. Chromophores obtained with sodium periodate (NaIO4) and tert-butyl hydroperoxide from both sialic acids and 2-deoxyribose can remain stable for several hours at room temperature, whereas when heated to 100°C they degrade within a few minutes. However, when the reaction mixture is exposed to alkaline solutions, only the chromophores derived from sialic acids degrade to a colorless state, whereas the chromophore derived from 2-deoxyribose retains its color. In addition, it should be noted that the contributions of N-acetylneuraminic acid and N-glycolylneuraminic acid to the formation of the above-mentioned chromophores also differs. This is evidenced by the fact that the molar absorption coefficient of N-glycolylneuraminic acid is 19% lower than that of N-acetylneuraminic acid, which may indicate differences in the bond strength of the acetyl and glycolyl groups in sialic acids. Thus, the methods developed to date make it possible not only to perform highly sensitive and selective qualitative and quantitative assay of various gangliosides present in biological samples, but also to effectively determine the activity of sialidases involved in hydrolysis of these gangliosides. However, because this requires quite complex, expensive, and technically demanding high-performance liquid chromatography with fluorescence detection, the more widely accepted approach in routine biochemical studies of gangliosides and sialidases remains the simpler optical-chemical method based on the use of thiobarbituric acid.