Choline Chloride Based Deep Eutectic Solvents as Promising Extractants of Flavonoids from Sedative Plant Composition

Introduction. Nowadays deep eutectic solvents (DESs) are the object of close attention of the scientific community in various fields, such as chemistry, biology, pharmacy, biotechnology. The areas of application of DESs vary widely, and one of them is the extraction of biologically active substances from plant raw materials. Aim. The aim of this work was to study the possibility of extraction of flavonoids from plant raw materials with using of deep eutectic solvents based on choline chloride, as well as to compare the efficiency of their extraction with traditional solvents. Materials and methods. The extraction of flavonoids was carried out from the collection of a plant composition consisting of the herb of motherwort cordial (common motherwort) ( Leonurus cardiaca L.), the herb of St. John's wort ( Hypericum perforatum L.), the herb of lemon balm ( Melissa officinalis L.) and the herb of creeping thyme (thyme) ( Thymus serpyllum L.) in a ratio of 4 : 2.5 : 2.5 : 1, crushed to a particle size of 2–3 mm. DESs based on choline chloride as hydrogen bond acceptor were used as extractants. Results and discussion. In this article, DESs based on choline chloride were investigated for the ability to extract flavonoids from the medicinal collection of a plant composition based on leonurus grass, hypericum grass, melissa grass and thyme grass, which has a sedative effect. The influence of the water content in DES solutions on the properties of the extractant was also studied. Quantitative determination of flavonoids in terms of rutin was carried out by differential spectrophotometry at a wavelength of 410 ± 2 nm. The maximum yield of flavonoids was achieved by using a 50 % aqueous solution of DES based on choline chloride, glucose and water in a molar ratio of 2 : 1 : 1 at an extraction temperature of 60 °C. Conclusion. The extracting ability of the obtained DES in terms of the efficiency of flavonoid extraction exceeds the extracting characteristics of the classical extractant for the composition under study – 70 % ethanol. Further study of the properties of the obtained extractant, its physical, chemical, and toxicological characteristics is the task of future experiments.