Development of Theoretical Approaches to Determination of the Main Groups of Biologically Active Substances of Medicinal Plant Raw Materials by TLC Method

Introduction. As is known, the selection of optimal conditions for the analysis of extracts from medicinal plant raw materials (MPМ), as well as medicinal herbal preparations and pharmaceutical substances of plant origin, characterized by a complex variable composition of biologically active substances (BAS) by TLC, presents certain difficulties. For the design of mobile phases for the separation of mixtures of BAS of plant origin, in a thin layer of sorbent, the following approaches are used: literary sources; standard mobile phases; spot elution method; the scheme proposed by the firm Camag (Switzerland); model "PRISMA"; variocameras and others. In foreign literature, there are publications on the generalization of the available experimental data on the determination of various natural groups of BAS in objects of plant origin. However, such reviews did not reveal the regularities of the chromatographic behavior of individual BAS in a thin layer, as well as the influence of various factors on the reproducibility of R_f values. The study of the possibility of a theoretical approach to the choice of optimal conditions for chromatography of groups of BAS of different polarity, allowing them to separate, identify and quantify by TLC is a relevant and poorly developed area of chromatography in general.
Aim. The aim of this work was to develop a theoretical approach to the choice of optimal conditions for the chromatographic separation of various groups of BAS of plant origin in a thin layer of sorbent.
Materials and methods. To study the regularities of chromatographic behavior in a thin layer of representatives of the main classes of BAS present in MPМ (amino acids, flavonoids, tannins, simple sugars, ascorbic acid, fat-soluble vitamins), the value of the main factor affecting the parameters of the efficiency of the chromatographic process, the polarity of the eluent, was studied. As objects of research, we used ready-made chopped raw material of nettle leaves, produced by a domestic manufacturer, that meets the requirements of regulatory documents, as well as sea buckthorn fruits collected on the territory of the Voronezh region, according to the rules for harvesting MPМ of various morphological groups in fresh and dried form.
Results and discussion. The regularities of elution and mathematical models describing the chromatographic behavior of plant BAS in a thin layer of sorbent have been established. Based on the totality of the results obtained, from the standpoint of the efficiency of the chromatographic process, the optimal conditions for their TLC analysis were selected and theoretically substantiated. To study the qualitative composition of BAS and to achieve a clear separation of zones on chromatograms, TLC methods were developed and tested on the studied MPМ using simple, frontal or two-dimensional chromatography.
Conclusion. It is shown that the determination and separation in a thin layer of the sorbent of hydrophilic and lipophilic BAS of MPМ in the presence of a joint requires different approaches and techniques. The paper proposes an algorithm for the selection of the mobile phase and methods of chromatography of BAS of medicinal products. The revealed mathematical models describing the chromatographic behavior of BAS will make it possible to select the conditions under which it is possible to determine the individual components of multicomponent mixtures without preliminary separation. The developed methods for the determination of BAS can also be used for standardization and quality assessment of other types of MPМ, phytopreparations and pharmaceutical substances of plant origin.

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