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A comparative pharmacognostic study of two lowland wood-grass peats of different origin from the Tomsk oblast deposits and of the physicochemical parameters of the structure of humic acids (HAs) isolated therefrom was carried out in order to substantiate the interchangeability of peat raw materials classified into the same peat type and to select a promising source of biologically active HAs for development of new drug candidates with non-specific biological activity. It was found that two lowland wood-grass peats of different origin from the Tomsk oblast deposits (Klyukvennoe and Tagan peatlands) have similar botanical compositions and pharmacognostic parameters. Humic acids were isolated from the peats by alkaline extraction and, according to a combination of physicochemical methods (UV and IR spectroscopy, elemental CHNS analysis, 13C-NMR spectroscopy, titrimetry), have common structural features due to the presence of the aromatic structure substituted with aliphatic radicals and of the polyconjugated system, identical aromaticity degrees, the predominance of hydrophilic over hydrophobic moieties, polydispersity, and pronounced reducing properties. This indicates the interchangeability of the peat raw materials, provided that the technology for HAs extracting from the peat is observed. The revealed distinctions between the HA samples, mainly in terms of the nitrogen content and the content of phenolic and quinoid moieties, the degree of condensation of aromatic structures, and the contents of lignin methoxy group and of carbohydrate moieties, made it possible to conclude that the HAs extracted from the Tagan deposit peat are more promising raw materials for the development of safe plant-based medicines effective in the prevention and treatment of a wide range of pathologies. [ABSTRACT FROM AUTHOR]