Study of phenolic compounds in Cosmos bipinnatus Cav. raw materials by HPLC

Abstract

Introduction.       The genus Cosmos has approximately 25 species. Representatives of this genus are common in the southwestern United States and Mexico. Cosmos bipinnatus (Cav.) of the aster family (Asteraceae) is one of the most famous ornamental plants of this genus, which are widely cultivated in Ukraine. The chemical composition of the plant is being studied by scientists from many countries around the world. Phenolic compounds, which cause a wide range of their pharmacological activity, attract the special attention of researchers. This fact determines the expediency of studying these compounds in the raw materials of bipinnate cosmea of domestic origin for the selection of promising raw materials, further standardization and development of medicinal products based on it. Materials and methods. Grass, leaves, flowers, stems and seeds of Cosmos bipinnatus (Cav.) were used for research. Grass, leaves, flowers and stems were collected in the flowering phase of the plant in July-August, seeds - in August-September 2021/2022 in the Kharkiv region (Ukraine). To remove phenolic compounds, the raw material was extracted as follows: 0.500 g of crushed raw material was placed in a 100 ml conical flask equipped with a reflux condenser, 25 ml of 70% ethanol was added and heated in a water bath for 45 minutes. The resulting solution was then cooled to room temperature and filtered through a red tape filter into a 25.0 ml volumetric flask. The volume of the solution was adjusted to 25.0 ml with 70% ethanol. The chromatographic study of tested herb specimens was performed at a Shimadzu HPLC-system, ser.20 liquid chromatograph equipped with a diode matrix detector under the following conditions: Phenomenex Luna C18 column, dimensions: 250 mm х 4,6 mm, particle size 5 μm; column temperature 350С; detector wavelength 330 nm; mobile phase flow rate 1 ml/min; introduced sample volume 5 μl.  The components were identified by their retention time and conformity of their UV spectra to standard substance. Research results. 11 flavonoids and 11 phenolic acids were identified in the grass and flowers of Cosmos bipinnatus (Cav.), in the leaves of this plant - 10 flavonoids and 11 phenolic acids, in the stems - 10 flavonoids and 10 phenolic acids. Luteolin-7-glucuronide was not detected in the leaves and stems of Cosmos bipinnatus (Cav.), vanillic acid was not identified in the stems. The qualitative composition of the phenolic compounds of the seeds differed from the composition of the other studied types of raw materials. In terms of quantitative content, isoquercitrin, quercetin, rutin, hydroxybenzoic and p-coumaric acids prevailed in the grass and leaves of Cosmos bipinnatus (Cav.), in stems - rutin, luteolin, apigenin, hydroxybenzoic, ferulic and p-coumaric acids, in flowers - isoquercitrin, luteolin, apigenin, hydroxybenzoic, p-coumaric, chlorogenic and caffeic acids. Quercetin, quercetin-3-O--glucopyranoside and ferulic acid were the major flavonoids in the seeds of Cosmos bipinnatus (Cav.). The content of the identified substances was higher in the grass, leaves and flowers of the studied plant. The lowest value of their content was recorded in the stems and seeds of Cosmos bipinnatus (Cav.). Conclusions. The obtained experimental data indicate the predominant accumulation of flavonoids and phenolic acids in the grass, leaves and flowers of cosmea bipinnate of Ukrainian origin. Research results will be taken into account when choosing promising raw materials bipinnate cosmeia, further standardization and development of medicinal products based on it.

Keywords: Cosmos bipinnatus (Cav.), phenolic compounds, HPLC.