Corresponding author: Kseniya Proskurina ( ksenapharm@yahoo.com ) Academic editor: Guenka Petrova
© 2021 Kseniya Proskurina, Olga Yevtifieieva, Olga Mala, Viktoriya Mashtaler.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Proskurina K, Yevtifieieva O, Mala O, Mashtaler V (2021) Development of the method for standardization of the medicinal plant raw material of Cichorium intybus L. herb by the total amount of hydroxycinnamic acid derivatives. Pharmacia 68(1): 167-173. https://doi.org/10.3897/pharmacia.68.e49273
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The purpose of the research is to work out a routine method for the quantitative determination of the total amount of hydroxycinnamic acids in chicory herb growing in Ukraine. The presence of chlorogenic and caffeic acids was experimentally proven by comparing the TLC profiles of solutions of the chicory extract and standard substances of hydroxycinnamic acids. According to the chromatogram, the chemical composition of the ethanol extracts was qualitatively constant and did not depend on the series of plants collected in different places (7 regions of Ukraine) and in different years (2017 and 2018). The water-alcohol solutions of 8 chicory herb samples had the absorption maximum at the wavelength range from 326 to 330 nm, which was typical for phenolic acids. Chlorogenic acid was chosen as a marker substance for the quantitative determination by direct spectrophotometry. The value of the specific absorbance (556.21(λ=327 nm)) of chlorogenic acid in the concentration of 10.08 µg/ml in ethanol 50% was determined. The total amount of hydroxycinnamic acids was found to be 1.87% for the sample of 2017, for the samples of 2018 in the range of 4.00–6.61%. The method proposed is acceptable for standardization of the medicinal plant raw material.
Cichorium intybus L., Quantitative Determination, Total Hydroxycinnamic Acid Derivatives, UV-visible Spectrophotometry
Since the 18th century chicory has been appreciated as a medicinal plant in many civilizations for centuries (
Despite this and the long tradition of its use, the medicinal plant raw material of chicory has not been standardized. Chicory has not been described in the European Pharmacopoeia or in any official Pharmacopoeias of the European Union member states (
The chemical composition of chicory has been well studied. More than 100 individual compounds were isolated and identified (
The most important activity of chicory is the antioxidant one (
The aim of this work is to develop a routine spectrophotometric method for the quantitative standardization of chicory herb as the medicinal plant raw material growing in Ukraine. The previous qualitative phytochemical analysis is intended to identify the presence and the composition of hydroxycinnamic acids and choose phenolic acid as the standard by which the total amount of hydroxycinnamic acids will be expressed. To determine the amount of hydroxycinnamic acids in the medicinal plant selected it is necessary to develop a procedure using spectrophotometry.
Eight samples of chicory herb (Cichorium intybus L.) were used as the research objects, some of them were purchased at the pharmacy, and the rest were collected during the flowering period from May to September in different regions of Ukraine. The data about the series and the place of harvesting and / or manufacturer for the preparation of test solutions are presented in Table
Authentic standards of chlorogenic acid (3-O-caffeoylquinic acid) (CA, ≥ 97,5 %), caffeic acid (3,4-dihydroxycinnamic acid) (> 99%), ferulic acid (4-hydroxy-3-methoxycinnamic acid) (99%) were purchased from Acros Organics BVBA (Janssen Pharmaceuticalaan 3a 2440 Geel, Belgium). Authentic standards of hyperoside (quercetin 3-d-galactoside) (98,23%), 2-aminoethyl diphenylborinate (97%), macrogol 400 were purchased from Sigma-Aldrich (Saint Louis, MO, USA). Other reagents and solvents used were of analytical grade.
Phenolic acid was defined by unified pharmacopoeal TLC-methods for identification of phenolic acids (
Test solution. To 0.5 g of the powdered herb (355) (2.9.12) (
Reference solution. Dissolve 2.0 mg of chlorogenic acid and 2.0 mg of caffeic acid in 10 ml of methanol.
Mobile phase: Anhydrous formic acid, glacial acetic acid, water, ethyl acetate (11:11:27:100 V/V/V/V).
Application: 10 μL as bands of 10 mm.
Drying: in air.
Detection: heat at 100–105 °C for 5 min; spray the warm plate with 10 g/L solution of 2-aminoethyl diphenylborinate in methanol followed by 50 g/L solution of macrogol 400 in methanol; examine in ultraviolet light at 365 nm.
The Rf value was calculated for the areas of chlorogenic acid and caffeic acid markers when studying by various analysts for three days. The results were expressed as RSD,%.
An UV/Vis a Specord 200 – 220U213 spectrophotometer (Analitik Zena, Germany) and 1-cm quartz cells were used for all absorbance measurements.
Model solution of chlorogenic acid for UV-spectrophotometry: weigh 25 mg of the sample of the standard of chlorogenic acid and dissolve in 100.0 ml of ethanol (50 per cent V/V). Dilute the solution portions of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 ml to 50.0 ml with ethanol (50 per cent V/V).
Each solution was measured three times.
To 0.500 g of the powdered herb add 80 ml of ethanol (50 per cent V/V), and boil the mixture on a water bath under a reflux condenser for 30 min. After cooling, filter the extract, and rinse the filter with 10 ml of ethanol (50 per cent V/V). Dilute a combined filtrate and the rinsings to 100.0 ml in a volumetric flask with ethanol (50 per cent V/V), and the resulting solution is used as a stock solution. Prepare the test solution by diluting 2.0 ml of the stock solution to 50.0 ml with ethanol (50 per cent V/V). Ethanol (50 per cent V/V) is used as a compensation solution. The absorbance of the test solution is measured immediately at 327 ±2 nm.
All analyses were performed in triplicate.
The total amount of hydroxycinnamic acids (X, %) expressed as chlorogenic acid was calculated according to the formula:
,
where A – is the absorbance of the test solution at 327 nm;
m – is the mass of the powdered herb to be examined, g;
W – is the loss on drying (%);
– is the specific absorption index of chlorogenic acid at 327 nm (= 556.21).
Performance characteristics of the analytical procedures for the total amount of hydroxycinnamic acids were determined taking into account the valuable prevalidation strategy (
The presence of hydroxycinnamic acids in ethanolic extracts of aerial parts of chicory was identified using thin-layer chromatography (TLC). The results are presented in Figure
The results obtained when determining precision showed that the areas identified on the chromatograms were identical with respect to their number, fluorescence intensity; they were placed in parallel and clearly. The metrological characteristics of determining the areas (Rf) of marker substances for chlorogenic acid were: Rf average = 0.483; RSD = 2.08%; for caffeic acid: Rf average = 0.886; RSD = 1.15%.
According to
The results of the comparative analysis of the methods for the quantitative determination of the total amount of hydroxycinnamic acids by spectrophotometry in various plant objects growing in the territory of the Commonwealth of Independent States (CIS) are presented in Table
The results of the comparative analysis of the sample preparation of methods for the quantitative determination of the total amount of hydroxycinnamic acids in plant objects of the CIS by UV spectrophotometry calculated with reference to the specific absorbance of chlorogenic acid.
No. | Plant | Raw material | Extraction | The number of additional repetitions of the extraction | The wavelength (λ) , nm | Reference | ||
---|---|---|---|---|---|---|---|---|
Extractant | Minutes on a water bath | |||||||
1 | Inula helenium L. | roots and rhizomes | ethanol (50a) | 45 | 2 (15 min.) | 325 | 531 | ( |
2 | Cichorium intybus L. | roots | ethanol (50a) | 30 | 2 (15 min.) | 325 | 556 | ( |
3 | Prunus domestica L. | leaves | ethanol (20a) | 60 | 1 | 327 | 531 | ( |
4 | Polygonum persicaria L. | herb | ethanol (70a) | 30 | 1 | 330 | 507 | ( |
5 | Urtica dioica L. | leaves | ethanol (70a) | 30 | 1 | 328 | 507 | ( |
6 | Galinsoga parviflora | herb | ethanol (70a) | 30 | 0 | 330 | 504 | ( |
7 | Cynara scolymus L. | inflorescences | water | 15 | 2 | 327 | 531 | ( |
By applying the selected extractant the aqueous alcohol extracts for different samples of chicory herb were obtained. The electronic absorption spectra of this solution are presented in Figure
The maxima of wavelength of electronic absorption spectra obtained for different samples of chicory herb originating from Ukraine.
No of the sample | Abbr. | Maximum absorptiona at a wavelength of | ||||||
325 nm | 326 nm | 327nm | 328nm | 329 nm | 330nm | 331nm | ||
1 | CI 118 | 0.4665 | 0.4688 | 0.4681 | 0.4685 | 0.4685 | 0.4666 | 0.4648 |
2 | CI 218 | 0.5056 | 0.5085 | 0.5083 | 0.5083 | 0.5087 | 0.5067 | 0.5042 |
3 | CI 318 | 0.7052 | 0.7080 | 0.7118 | 0.7142 | 0.7153 | 0.7170 | 0.7161 |
4 | CI 418 | 0.7113 | 0.7173 | 0.7189 | 0.7233 | 0.7234 | 0.7238 | 0.7238 |
5 | CI 518 | 0.5811 | 0.5838 | 0.5856 | 0.5863 | 0.5866 | 0.5858 | 0.5855 |
6 | CI 618 | 0.4350 | 0.4361 | 0.4363 | 0.4393 | 0.4386 | 0.4392 | 0.4393 |
7 | CI 717 | 0.4388 | 0.4401 | 0.4410 | 0.4411 | 0.4414 | 0.4400 | 0.4387 |
8 | CI 817 | 0.2106 | 0.2111 | 0.2104 | 0.2098 | 0.2085 | 0.2075 | 0.2063 |
9 | Ch.ac. | 0.5485 | 0.5527 | 0.5562 | 0.5583 | 0.5591 | 0.5591 | 0.5574 |
The aqueous alcoholic solution of chicory is an unstable mixture of substances known and unknown, which to some extent can not only absorb optical density, but also interact with each other. In principle, it is impossible to verify the additivity of light absorption, i.e. to take into account the influence of other components, mixtures with an incompletely known composition (
To select a substance for which the content of the total amount of hydroxycinnamic acids was calculated, the absorption spectrum of the solution of the chlorogenic acid standard was measured. The absorption spectrum is presented in Figure
The performance characteristics of the method were previously determined taking into account the valuable validation strategy (
Limiting values, such as the limiting signal value, limit of detection and limit of quantification, were estimated using the analytical evaluation function. The limit of quantification (LOQ) was found to be 0.37 µg/ml, while the limit of detection (LOD) was 0.12 µg/ml.
The relationship between optical density and the chlorogenic acid content was determined by the least squares method. The linear dependence of the method was described by the equation y = 0.9750× + 0.0264 and the correlation coefficient R² = 0.9998 in the working range from 2.52 to 15.12 μg/ml. The standard deviation of the angular coefficient of the linear dependence Sb = 0.0037, and the standard deviation of the free term of the linear dependence Sa = 0.0366 were also determined.
The following precision parameters were studied: the standard deviation calculated for the “Found / Introduced” ratios for model solutions of chlorogenic acid SD = 0.84%, one-sided confidence interval ΔZ = 1.69%.
The determination of the total amount of hydroxycinnamic acids calculated with reference to chlorogenic acid at the wavelength of 325, 327, 328, 330 nm was reported; it could be substantiated by the different concentration of ethanol during extraction as shown in Table
The samples of chicory herb studied were analyzed using the method developed. The results are presented in Table
The content of the total amount of hydroxycinnamic acids in chicory herb originating from Ukraine.
No of the sample | Region of Ukraine | Year of collection | Abbr. | Content (%)±SDa |
---|---|---|---|---|
1 | LLC Pharmacy (Kharkiv region) | 2018 | CI 118 | 4.21±0.14 |
2 | Collected wild (Sumy region) | 2018 | CI 218 | 4.57±0.59 |
3 | Collected wild (Kharkiv region) | 2018 | CI 318 | 6.51±0.73 |
4 | “Mir trav” (Zakarpattia region) | 2018 | CI 418 | 6.61±1.92 |
5 | “Lechec” (Kropyvnytskyi region) | 2018 | CI 518 | 5.25±0.88 |
6 | “Kladez Market” (Poltava region) | 2018 | CI 618 | 4.01±0.21 |
7 | LLC Pharmacy (Chernihiv region) | 2017 | CI 717 | 4.00±0.37 |
8 | “Sumyfitofarmacia” Ltd (Sumy region) | 2017 | CI 817 | 1.87±0.55 |
Phenolic substances have been identified by comparing TLC profiles of the ethanol extract of chicory and solutions of standard substances of hydroxycinnamic acids. On the chromatogram of the solutions studied the intense areas with a greenish-blue fluorescence are found at the level of the areas of the standard solutions of chlorogenic and caffeic acids.
The spectrophotometric procedure for the quantitative determination of the total amount of hydroxycinnamic acids calculated with reference to chlorogenic acid has been developed. To estimate the possible influence of environmental factors, the total amount of hydroxycinnamic acids in 8 chicory samples from different regions of Ukraine and different years of collection has been determined. The content of hydroxycinnamic acids is 1.87% for the chicory sample of 2017, from 4.00% to 6.61% for the samples of 2018. It can be explained by the loss of active substances during storage. The method proposed has several advantages: it is an easy, fast, “greenest” and inexpensive method, available today in most laboratories.
This study was supported by the Ministry of Health of Ukraine (Number of the project: 0114U000949).