Phytochemical analysis of the main groups of secondary metabolites in the Dracocephalum moldavica L. herb

Abstract

The genus Dragonhead (Dracocephalum L.) includes 72 species of essential oil-bearing plants belonging to the Lamiaceae family. Many of them have long been used in a folk medicine of different countries. Moldavian dragonhead (D. moldavica L.) has been identified as the most promising species for the complex phytochemical research since it was successfully introduced in the climatic conditions of the Ukrainian forest-steppe zone and due to the presence of its various botanical forms and varieties. The aim of this study was the phytochemical analysis of the main groups of secondary metabolites in the herb of violet-flowered form of Moldavian dragonhead  (D. moldavica L.) under its cultivation in Ternopil region (Ukraine). The herb of the plant was harvested in July of 2018‒2019 years during the flowering period. The essential oil was obtained from the plant raw material by the hydrodistillation. Such physical and chemical parameters of the essential oil as a relative density, refractive index, optical rotation, acid number and solubility in ethanol were studied. The method of thin layer chromatography (TLC) was used to determine the specific sequence of bands in the chromatograms of essential oil. The method of high-performance thin-layer chromatography (HPTLC) was used for the identification of phenolic compounds in the herb. The component composition of polyphenols was determined by the high performance liquid chromatography (HPLC). The specific physical and chemical parameters as well as the «chromatographic profile» of essential oil have been established. The main compounds of the polyphenolic nature were revealed by the chromatographic methods. In particular, rosmarinic and caffeic hydroxycinnamic acids were identified in the methanol extract of herb by the HPTLC method. The HPLC analysis of phenolic compounds in the 70% ethanol extract of raw material established that rosmarinic acid was its main polyphenol. It was found the decreasing of polyphenol contents in the D. moldavica herb in such direction: rosmarinic acid (3.01%) > apigenin-7-О-glucoside (0.67%) > apigenin (0.29%) > caffeic acid (0.28%) > luteolin-7-О-glucoside (0.13%)> hyperoside (0.12%) > ferulic acid (0.09%) > chlorogenic acid (0.08%). The obtained data could be used for planning pharmacological studies of the phytosubstances developed from the Moldavian dragonhead herb.