RU2493555C1 - Infrared spectroscopic express method of determining quality of medicinal plant material - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method involves selecting medicinal plants, crushing, analysing samples of the medicinal plant material, wherein the medicinal plant material is crushed to particle size of 0.2÷0.5 mm. The obtained sample is put into an ATR attachment and an infrared spectrum is recorded on a Fourier transform infrared spectrometer; values of characteristic frequencies of the infrared spectrum, which correspond to chemical composition of the sample, are identified and the medicinal plant material is identified using tables of spectral data for reference samples of medicinal material. Safety and quality of the medicinal plant material is determined from presence of functional groups in the sample that are not characteristic of chemical composition of medicinal plants and resulting from anthropogenic contamination.

EFFECT: invention increases control efficiency.

2 dwg

Description

The invention relates to the field of pharmacology and medicine and relates to a method of rapid analysis with the determination of the authenticity of medicinal raw materials by Fourier-IR spectroscopy.

A known method for determining the authenticity of plant materials according to the current state standard: GOST 24027.1-80. Herbal raw materials. Methods for determining the authenticity, infection with barn pests, crushing and content of impurities, 01/01/1981 (analog).

This method relates to methods for determining the authenticity of medicinal raw materials, infection with barn pests, grinding and the content of impurities.

The method includes the steps of:

- sampling of medicinal raw materials in accordance with GOST 24027.0-80. Herbal raw materials. Acceptance rules and sampling methods. For this purpose, point samples are taken from a batch (not less than 50 kg) of plant material from different places of the bag or bale, then point samples are combined into a combined sample, from which the average sample is extracted by quarting, further work is carried out with an average sample;

- determination of the authenticity of medicinal raw materials: visually or using a magnifying glass, by the size of the raw materials using a ruler, visually by color in daylight, organoleptically by smell, organoleptically by taste;

- the preparation and study of micropreparations from leaves, herbs, flowers, fruits, seeds, etc .; for this, several pieces of raw materials are placed in a test tube with caustic alkali and boiled for 1-2 minutes, then the liquid is drained, the pieces are washed and placed in glycerol solution, then the pieces are removed and placed on a glass slide, covered with a coverslip and examined under a microscope, determined by anatomical diagnostic signs of appropriate raw materials;

- conducting qualitative microchemical reactions to the detection of biologically active substances in each specific raw material, for each group of compounds its own reactions, for example, tannins are detected using a solution of iron-ammonium alum or iron chloride;

- grinding - an average sample of the raw material is placed on a sieve specified in the regulatory technical document for a specific raw material, and sieved in portions, work with the passage of raw materials from the sieve;

- the determination of the content of impurities consists in placing the crushed parts on a smooth surface and with tweezers emit impurities: organic (parts of the same plant or impurities of other plants; twigs, hay, straw) and mineral (sand, earth, stones);

The disadvantages of this known method include

- the duration of the preparation of instruments and materials;

- the duration of the test;

- the impossibility of determining the presence of pollutants in the medicinal raw materials, since in the known method the impurities include - foreign parts that got into the raw materials during the harvesting process: organic (parts of the same plant or impurities of other plants; rods, hay, straw) and mineral (sand, earth , stones);

- the inability to identify the chemical nature of pollutants in medicinal raw materials;

- the impossibility of accurately determining the type of plant by this method, since some plants, having exactly the same appearance, smell and taste, differ in cost tens of times, which provokes suppliers to add cheap “filler” to expensive medicinal raw materials.

The elimination of these disadvantages is achieved in the proposed method.

A known method of assessing the state of the environment [RU 2410670], comprising the steps of:

- registration of the reflection spectrum of the electromagnetic radiation of dandelion leaves in the visible range (400 ÷ 750 nm);

- determination of the relations of the coefficients of spectral brightness at specific wavelengths;

- correlation analysis with a standard.

The disadvantages of this known method include:

- lack of universality of the method using only one indicator plant;

- insufficient information content of the obtained spectral parameters;

- the need for additional calculations based on the results of several measurements with a spectrometer, which leads to both an increase in the error and an increase in the analysis time, which is a significant drawback in the case of the express method.

Known Method for the classification of medicinal plants using infrared Fourier spectroscopy in the near field using a Thermo Scientific Anteris II analyzer (Classification of medicinal plants using infrared Fourier spectroscopy in the near field using a Thermo Scientific Anteris II analyzer // Pharmaceutical Technologies and Packaging, 2011. No. 3. S.64-65) (prototype), including the stages:

- placement of standard samples of medicinal raw materials, with various degrees of grinding, in a closed rotating cup of the Thermo Scientific Anteris II analyzer;

- 50-fold scanning of samples using the Anteris II system in the near range of 10000 ÷ 4000 cm ^-1 with a resolution of 4 cm ^-1 ;

- classification of the spectra of samples using the Thermo Scientific TQ Analyst system.

The disadvantages of the prototype include:

- the impossibility of determining the presence of pollutants in medicinal raw materials and identifying their chemical nature;

- the need for multiple scans to obtain averaged spectral parameters;

- the impossibility of using the most informational average measurement range in the IR region of 4000 ÷ 400 cm ^-1 , in which most signals of organic compounds are located, and the transitions between the vibrational states of the ground electronic state are mainly due to the absorption of infrared radiation.

The technical result of the claimed invention consists in the development of an express method for determining the authenticity of medicinal plant materials, the development of a qualitative determination of pollutants in medicinal plant materials by rapid analysis based on IR spectroscopy.

The technical result of the invention is achieved in that the proposed method for determining the authenticity of raw materials and the content of pollutants in medicinal plant materials contains the stages:

- sampling of medicinal raw materials in accordance with GOST 24027.0-80. Herbal raw materials. Acceptance rules and sampling methods. For this purpose, point samples are taken from a batch (not less than 50 kg) of plant material from different places of the bag or bale, then point samples are combined into a combined sample, from which the average sample is extracted by quarting, further work is carried out with an average sample;

- grinding of medicinal raw materials up to 0.2 ÷ 0.5 mm (for example, in a vibratory mill);

- express analysis of the sample using the Golden Gate Diamond ATR Series MkII single-time ATR attachment with Specac artificial diamond (ATR attachment) on an Equinox 55 Fourier-IR spectrometer (Bruker);

- identification of values of characteristic frequencies corresponding to the chemical composition of plants, and determination of the authenticity of raw materials using spectral tabular data;

- identification of functional groups in the sample of plant materials that are not characteristic of the chemical composition of the plant and appeared as a result of anthropogenic pollution, the identification of the chemical nature of pollutants in medicinal raw materials, depending on the place of growth of the raw material.

The problem is solved due to the fact that, in contrast to the prototype, which has common technological steps with the proposed method, namely the use of Fourier-IR spectroscopy to determine the authenticity and purity of medicinal plant materials, the following differences are provided:

- averaging of characteristics is achieved not due to a 50-fold scanning of samples with further statistical processing of the results, but due to additional grinding of the average sample of a standard medicinal plant material up to 0.2 ÷ 0.5 mm;

- the prototype uses a range of 10000 ÷ 4000 cm ^-1 - the near infrared region of the electromagnetic spectrum, corresponding to the manifestation of only overtones of the fundamental oscillations and composite frequencies, whereas in the proposed method, measurements are carried out in the most informational average infrared region of the electromagnetic spectrum 4000 ÷ 400 cm ^-1 , where most of the signals of organic compounds and transitions between the vibrational states of the ground electronic state are located;

- unlike the analogue, the proposed method is characterized by speed and accuracy due to the minimum time required for sample preparation, which is achieved by using an ATR attachment to record IR spectra of plant samples that do not require special sample preparation - a standard drug sample is placed in the console and scanned by Fourier-IR spectrometer "Equinox 55" ("Bruker").

The inventive method is illustrated in tables and graphic materials.

Figure 1. - IR spectra in the range of 400-000 cm ^-1 and 400-2000 cm ^-1 samples of the rhizomes of the potentilla erect Potentilla erecta (L.) Raeusch., Collected: I - in the background zone (Ostashkovsky district of Tver region, Lake. Sig - Specially Protected Natural Territory) and II - Tver, CHPP-3 channel - a site of environmental tension (SO ₂ , NO _x , particulate matter).

Figure 2. - Nuclear spectra in the range of 400-4000 cm ^-1 and 400-2000 cm ^-1 color samples of a series of tripartite Bidens tripartita L., collected: I - in the background zone (Ostashkovsky district of Tver region, Lake Sig - Specially protected natural territory) and II - the city of Tver, the CHPP-3 channel - a node of environmental tension (SO ₂ , NO _x , solid particles)

Table 1. Interpretation of the absorption bands of samples of medicinal plants (Potentilla erecta (L.) Raeusch., Bidens tripartita L.).

The essence of the proposed method is as follows.

The increased anthropogenic factor and attempts to falsify medicinal plant materials require a more thorough analysis of the medicinal material. There is a need for a method of rapid analysis of plant materials entering the pharmaceutical industry, which allows you to quickly and reliably control the chemical composition of medicinal plants and the authenticity of the raw materials using spectral tables.

The inventive method based on IR spectroscopy plays a paramount role, as some plants, having exactly the same appearance, smell and taste, differ in cost by tens of times, which provokes suppliers to add cheap raw materials to expensive raw materials, which, ultimately, reduces the quality of drugs.

The inventive method is applicable in the determination of anthropogenic contamination of medicinal plants through the detection of functional groups in samples of plant materials that are not characteristic of the chemical composition of the plant and appeared as a result of anthropogenic impact. The inventive method makes it possible to subsequently identify the chemical nature of pollutants in the medicinal raw material based on the location of the growth of medicinal plant material.

The inventive method is based on the method of Fourier transform infrared spectroscopy. This is a universal physicochemical method that is used to study the structural features of various organic and inorganic compounds. A beam of infrared radiation is passed through the prototype. The substance absorbs part of the energy of the beam at a strictly defined frequency. When recording these energy absorption frequencies, a unique absorption spectrum of the medicinal plant is obtained, and positive identification of the medicinal plant becomes possible by comparing the obtained spectrum with the spectral tables of medicinal plants.

The inventive method is an alternative to traditional long-term methods of identification and classification (for example, descriptive morphology, microscopy, thin-layer and paper chromatography) of plant materials used in drugs. This can significantly save time and labor for the correct classification of incoming materials.

The inventive method includes the steps of:

- sampling of medicinal raw materials in accordance with GOST 24027.0-80. Herbal raw materials. Acceptance rules and sampling methods. For this purpose, point samples are taken from a batch (not less than 50 kg) of plant material from different places of the bag or bale, then point samples are combined into a combined sample, from which the average sample is extracted by quarting, further work is carried out with an average sample;

- standard grinding - an average sample of the raw material is placed on a sieve specified in the regulatory and technical document for a specific raw material, and sieved in portions, work with the passage of raw materials from the sieve;

- for further analysis, additional grinding of medicinal plant materials up to 0.2 ÷ 0.5 mm;

- an express recording of the IR spectra of individual parts of medicinal plants is performed using the ATR attachment of plant samples that does not require special sample preparation - a standard medicinal sample is placed in the console and scanned on an Equinox 55 Fourier transform IR spectrometer (Bruker);

- identification of values of characteristic frequencies corresponding to the chemical composition of plants and determination of the authenticity of medicinal raw materials using spectral tabular data;

- identification of functional groups in the sample of plant materials that are not characteristic of the chemical composition of the plant and appeared as a result of anthropogenic pollution, revealing the chemical nature of pollutants in the medicinal raw material, depending on the place of growth of the medicinal raw material.

To develop the proposed method of analysis, we studied the most common medicinal plants used in both official and traditional medicine. The proposed method obtained spectral tables of samples of pharmacologically significant parts (inflorescences, leaves, stems, roots and rhizomes) of medicinal plants (Potentilla erecta L., Bidens tripartite L., Hypericum perforatum L., Achillea millefolium L., Plantago major L., Lemna minor L. and others) used to identify the values of characteristic frequencies corresponding to the chemical composition of plants and determine the authenticity of medicinal raw materials.

The possibility of carrying out the claimed invention is shown by the following example.

For express acquisition of IR spectra, samples of medicinal plants, namely, rhizomes of P. erecta and B. tripartite flowers, were placed in the ATR attachment and spectra were recorded on a Bruker Equinox 55 Fourier-IR spectrometer in the range 400–4000 cm ^-1 . The duration of the analysis was 5 ÷ 10 minutes.

In the IR spectra of samples of rhizomes of P. erecta and flowers of B. tripartite there are absorption bands reflecting the general chemical composition of these parts of plants (Figs. 1 and 2). The presence of carbohydrates in the plant is evidenced by absorption bands (see table), due to the stretching vibration of CH ₂ groups at a frequency of ~ 2926 cm ^-1 and OH groups at frequencies of ~ 3390 cm ^-1 . The presence of proteins is indicated by absorption bands at frequencies of ~ 1615 cm ^-1 (Amide I), ~ 1520 (Amide II). The presence of fats can be judged by the presence of absorption bands at frequencies of ~ 1732 (ν _{C = O} ). The main changes in the IR spectra of the samples are observed in the region (400-1750 cm ^-1 ). In the spectra of samples from the background and contaminated zones, changes were detected in the region of stretching vibrations of the carbonyl and ether groups (ν _{C = O} ) ~ 1700, 1717, and 1741 cm ^-1 .

It was established that an increase in the intensity of the characteristic bands of the color spectra of the succession and rhizomes of the cinquefoil from a place with anthropogenic pollution is associated with oxidative processes that change the content of biologically active substances; the presence of sulfur dioxide emissions in the atmosphere by the CHPP-3 enterprise is indicated by the appearance in the IR spectra of medicinal plants of changes associated with the formation of the following compounds:

- sulfones - R-SO ₂ R 1318, 778, 533 cm ^-1

- sulfonic acids - R-SO ₂ -OH 1228 cm ^-1

- sulfates - (RO) ₂ SO ₂ 871 cm ^-1

The claimed method identified medicinal plants, revealed the authenticity of plant materials and found in samples of plant materials from a place with anthropogenic effects functional groups that are not characteristic of the chemical composition of the plant. The IR spectra of plant samples from different habitats have significant similarities, which indicates a certain resistance of the chemical composition of plants to anthropogenic effects.

The proposed method is intended for the pharmaceutical industry and medicine as an effective alternative method for controlling the quality of medicinal plant materials.

The proposed method was developed as part of a grant from the Fund for Assistance to the Development of Small Forms of Enterprises in the Scientific and Technical Field under the program "Participant of the Youth Scientific and Innovative Competition" ("U.M.N.I.K."), GK No. 8754r / 14008, 2011 2012 years and scientific cooperation was reached with Tver Pharmaceutical Factory OJSC, on the basis of which the method of express analysis of plant materials is tested.

Frequency, cm ^-1 Attributions ~ 3390 ν (OH), (NH) ~ 2926 ν _as (CH ₂ ) ~ 2855 ν _s (CH ₃ ) ~ 1732 ν (C = O) ~ 1710 ν (C = O) ~ 1615 Amide I ν (C = O) ~ 1520 Amide II ν (O-C-N) ~ 1446 δ (N-H) ~ 1360 δ (OH), (ν _COO ) ~ 1318 R-SO ₂ R, sulfones ~ 1228 R-SO ₂ -OH, sulfonic acids ~ 1073 ν _as (COC) ~ 1062 ν _as (COC) ~ 871 (RO) ₂ SO ₂ ~ 778 R-SO ₂ R, sulfones ~ 533 R-SO ₂ R

Claims (1)

An IR-spectroscopic express method for determining the quality of medicinal plant materials, containing the selection of medicinal plants, grinding, research of samples of medicinal plant materials, characterized in that: grinding of medicinal plant materials is up to 0.2 ÷ 0.5 mm; the resulting sample is placed in the ATR attachment without special sample preparation and the IR spectrum is recorded on a Fourier-IR spectrometer; identify the values of the characteristic frequencies of the IR spectrum corresponding to the chemical composition of the sample and determine the authenticity of the medicinal plant material from the table spectral data for the reference samples of the medicinal product; determine the presence of functional groups in the sample that are not characteristic of the chemical composition of medicinal plants and which have arisen as a result of anthropogenic pollution.

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