Comparative Characteristics of Sugar Determination by Different Methods in Leaves of Nettle

Introduction. According to the literature, nettle leaves contain polysaccharides and mucus as an integral part of the hydrophilic fraction. This group of biologically active substances (BAS) is involved in the manifestation of the physiological activity of the infusion. The traditional gravimetric method for the determination of polysaccharides in medicinal plant raw materials (PRM), pharmaceutical substances of plant origin and medicinal herbal preparations cannot provide a true picture of their content due to the presence of impurities. Therefore, it is advisable to determine the reducing sugars that are most fully extracted into the aqueous phase during the preparation of the infusion using modern physicochemical methods of analysis.

Aim. The aim of the work was to determine the amount of polysaccharides and simple sugars in nettle leaves by various physico-chemical methods and their comparative characteristics.

Materials and methods. A comparative determination of the sum of polysaccharides and simple sugars in the leaves of nettle by pharmacopoeial methods (picrine, anthrone and orcine) was carried out. Free and bound simple sugars were identified and quantified by thin layer chromatography (TLC). The composition and content of free simple sugars was studied by capillary electrophoresis (CE) in raw materials.

Results and discussion. The content of free and bound sugars in raw materials has been established. The largest content of both the sum of polysaccharides and free simple sugars in the polysaccharide complex of nettle leaves, as well as the sum of free reducing simple sugars, according to experimental data, was obtained using the picrine method. The content of pentoses in the studied PRM was four times less, which is consistent with the literature data on the preferential construction of polysaccharides of plant objects from sugars of the hexose class. The resulting total content of the fraction of free sugars in the leaves, determined by the CE method, is an order of magnitude less compared with spectrophotometric methods. The obtained results of quantitative determination of the amount of free and bound simple sugars in the studied PRM are consistent with the determination data by the picrine pharmacopoeial method.

Conclusion. In general, complete information, depending on the goals of the analysis, on the composition and quantitative content of simple and related sugars in the polysaccharide complex of plant objects can only be obtained by combining spectral methods with CE or TLC.

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