ISO/DIS 24825:2025(en)

ISO/TC 249/WG 2

Secretariat: SAC

Date: 2025-02-13

Traditional Chinese medicine — General principles for the establishment of herbal reference substances

© ISO 2025

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Contents

Foreword iv

Introduction v

1 Scope 1

2 Normative references 1

3 Terms and definitions 1

4 Establishment of herbal reference materials 2

4.1 Principle 2

4.2 Items for establishment 2

4.2.1 Requirements of raw materials 2

4.2.2 Preparation of herbal reference materials 2

4.2.3 Homogenization and assessment of homogeneity 3

4.2.4 Tests 3

4.2.5 Identification 3

4.2.6 Assay or purity determination 3

4.2.7 Assessment of stability 3

5 Establishment of herbal reference extracts 3

5.1 Principle 3

5.2 Items for establishment 3

5.2.1 Requirements of raw materials 3

5.2.2 Preparation of herbal reference extracts 3

5.2.3 Homogenization and assessment of homogeneity 4

5.2.4 Tests 4

5.2.5 Identification 4

5.2.6 Assay or purity determination 4

5.2.7 Assessment of stability 4

6 Establishment of herbal chemical reference substances 4

6.1 Principle 4

6.2 Items for establishment 5

6.2.1 Requirements of raw materials 5

6.2.2 Preparation of herbal chemical reference substances 5

6.2.3 Homogenization and assessment of homogeneity 5

6.2.4 Tests 5

6.2.5 Identification 5

6.2.6 Assay or purity determination 6

6.2.7 Assessment of stability 6

7 Quality control 6

8 Report 6

9 Instruction and labelling 6

10 Packaging 7

11 Storage and transportation 7

Bibliography 8

Foreword

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This document was prepared by Technical Committee ISO/TC 249, Traditional Chinese medicine.

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Introduction

The herbal reference substance serves as a benchmark for resolving disputes related to the quality of herbal medicinal products (HMPs). This standard outlines the principles for establishing herbal reference substances, considering the requirements of Chinese Pharmacopoeia, European Pharmacopoeia, Japanese Pharmacopoeia, Korean Pharmacopoeia, and the United States Pharmacopoeia. Insights from ISO 17034, ISO Guide 30, ISO Guide 31, ISO Guide 33, and ISO Guide 35 are also incorporated.

This standard promotes confidence among manufacturers, regulators, and consumers by providing a common basis for evaluating and verifying the quality of HMPs. It ensures that the herbal reference substances used in quality inspections and dispute resolutions meet recognized standards, enhancing fairness and reliability. Adherence to this standard aims to ensure consistent quality and safe usage of HMPs. This document is intended to help enterprises establish comprehensive production and supply chain management systems, enhancing product safety and traceability. Moreover, the document plays a significant role in harmonizing the different requirements to overcome the barriers to international trade, ensuring the sustainable growth and positive reputation of the global HMPs market.

It is important to note that this document not only provides comprehensive guidance for herbal reference substances but also encourages ongoing research, innovation, and collaboration among stakeholders to continuously improve quality standards in the field of herbal medicine.

Traditional Chinese medicine — General principles for the establishment of herbal reference substances

This document specifies the general principles for the establishment of herbal reference substances, covering terms and definitions, production, quality control, report, instruction and labelling, packaging, storage and transportation.

This document applies to herbal reference substances that are sold and used as reference standards for the quality control of herbal medicines in international trade, including raw materials and finished products.

The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 3864‑2, Graphical symbols — Safety colours and safety signs — Part 2: Design principles for product safety labels

ISO 17034, General requirements for the competence of reference material producers

ISO Guide 30:2015, Reference materials — Selected terms and definitions

ISO Guide 35, Reference materials — Guidance for characterization and assessment of homogeneity and stability

ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories

For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https://www.iso.org/obp

— IEC Electropedia: available at https://www.electropedia.org/

3.1

herbal reference substances

substances that are derived from herbal medicinal plants and used as reference standards in the physicochemical tests for the identification and qualification of raw materials and finished products of herbal medicines

Note 1 to entry: The physicochemical properties of herbal reference substances are well established. Herbal reference substances are divided into three types: herbal reference materials, herbal reference extracts, and herbal chemical reference substances.

3.2

herbal reference materials

certified and homogeneous substances containing powdered herbal medicine with clear origins and identification

[SOURCE: ISO Guide 30:2015, 2.1.1, modified.]

3.3

herbal reference extracts

certified and homogeneous substances containing a mixture of main effective ingredients or representative ingredients and unknown chemical components that are prepared by extracting herbal medicine with a specific process

3.4

herbal chemical reference substances

certified and homogeneous substances containing a single chemical component that are extracted, separated and purified from herbal medicine

[SOURCE: ISO Guide 30:2015, 2.1.2, modified.]

3.5

stability

characteristic of a reference substance, when stored under the specified time interval, packaging form and storage conditions, to maintain its property values within a specified content or composition

[SOURCE: ISO Guide 30:2015, 2.1.15, modified.]

3.6

homogeneity

state in which one or more properties of a reference substance have the same composition or structure

[SOURCE: ISO Guide 30:2015, 2.1.12, modified.]

The establishment of herbal reference materials includes requirements of raw materials, preparation of herbal reference materials, homogenization and assessment of homogeneity, tests, identification, assay or purity determination, and assessment of stability. In addition, more information such as analytical results obtained based on the requirements of national and regional pharmacopoeias (like ChP, EP, JP, KP, USP and others) should be made available. The requirement of local pharmacopoeias, legislation and standards should be considered and respected.

The raw materials should be herbs of the right species or subspecies and the right herbal parts, which should be clearly defined in phyto-taxonomy.

Information on raw materials shall be included as follows:

a) Collection: including specimen photographs of raw plants, harvest time, growing year and region, cultivated or wild;

b) Origin identification: including identification of botany and DNA;

c) Part selection: including selected parts, cleaning, cutting, and drying;

d) Storage: including storage conditions, packaging form;

e) Quality evaluation.

Herbal reference materials generally should be made by equipment and methods selected according to the characteristics of the individual raw material. Some raw materials need to be pre-treated to ensure the homogeneity and keep the original constituents to the maximum extent.

If necessary, measures of the produced batches should be taken for homogenization. Commonly used homogenization methods include crushing, mixing, and sieving.

A homogeneity test should be completed before qualification by testing, identification, assay and value assignment. Requirements for homogeneity assessment are specified in ISO Guide 35.

According to the properties of herbal reference materials, the corresponding test items and the necessary limits should be stipulated based on the test results of appropriate numbers of batches of samples.

Appropriate identification methods should be selected according to the properties of herbal reference materials, and the specificity and reproducibility of the methods should be paid attention to.

The identification items may include, but are not limited to macroscopic identification, microscopic identification, physicochemical identification, and biological identification.

Herbal reference materials are generally used for identification, so the assay is usually not performed.

Further studies should be conducted for the stability of herbal reference materials, including influencing factors, long-term and accelerated stability studies. Packaging forms and materials should be considered to provide a basis for the stability period, storage conditions, and use precautions.

In order to ensure the stability of herbal reference materials during their use, the developers should establish and implement procedures to ensure their long-term use reliability.

For the assessment of the stability, the results should be compared with those at product release.

The establishment of herbal reference extracts includes requirements of raw materials, preparation of herbal reference extracts, homogenization and assessment of homogeneity, tests, identification, assay or purity determination, and assessment of stability. In addition, more information such as analytical results obtained based on the requirements of national and regional pharmacopoeias (like ChP, EP, JP, KP, USP and others) should be made available. The requirement of local pharmacopoeias, legislation and standards should be considered and respected.

The raw materials should be herbs of the right species or subspecies and the right herbal parts, which should be clearly defined in phyto-taxonomy.

Alternative:

In order to provide appropriate reference materials, the necessary requirements, including those from standards or monographs for HMPs, are collected and evaluated in advance.

The extraction process of herbal reference extracts is preferably consistent or similar to that of the HMPs, or defined otherwise (like, total extract by ethanolic extraction).

Herbal reference extracts used for assay, necessary purification process should be taken. In order to ensure the relative consistency of composition and ratio of the compounds in the herbal reference extracts, a production of an appropriate number of batches should be prepared and examined to confirm the process and parameters.

If necessary, measures of produced batches should be taken for homogenization. Commonly used homogenization methods include dissolution, lyophilization, concentration, drying and mixing, or recrystallization.

A homogeneity test should be completed before qualification by testing, identification, assay and value assignment. Requirements for homogeneity assessment according to ISO Guide 35.

According to the properties of herbal reference extracts, the corresponding test items and the necessary limits should be stipulated based on the test results of appropriate numbers of batches of samples.

The test items may include, but are not limited to moisture, total ash, and solvent residue.

Appropriate identification methods should be selected according to the properties of herbal reference extracts, and the specificity and reproducibility of the methods should be paid attention to. The methods include macroscopic identification, physicochemical identification and biological identification.

Herbal reference extracts shall be used for identification and assay.

Generally, for herbal reference extracts established for identification purposes, only qualitative identification for main representative components or fingerprint should be established, and the assay is usually unneeded.

For herbal reference extracts for assay purposes, a specified content value should be assigned.

If possible, collaborative value measurement should be done by certified testing or production laboratories. For inter laboratory comparison of test results and to ensure the consistency of test methods, all participating laboratories should adopt the same test protocol and test record.

The test results should be subject to statistical processing and expressed by the mean value.

Further studies should be conducted for the stability of herbal reference extracts including influencing factors, long term and accelerated stability studies. Packaging forms and materials should be considered to provide a basis for the stability period, storage conditions, and use precautions.

In order to ensure the stability of herbal reference extracts during their use, the developers should establish and implement procedures to ensure their long-term use reliability.

Representative components or a characteristic chromatogram should be chosen to assess the stability.

Marker constituents of herbal reference extracts should be continuously monitored with the analytical methods that have been used for the determination of the original data for product release.

For the assessment of the stability, the results should be compared with those at product release.

The establishment of herbal chemical reference substances includes requirements of raw materials, preparation of herbal chemical reference substances, homogenization and assessment of homogeneity, tests, identification, purity determination, and assessment of stability. In addition, more extensive information such as analytical results obtained based on the requirements of national and regional pharmacopoeias (like ChP, EP, JP, KP, USP and others) should be made available. The requirement of local pharmacopoeias, legislation and standards should be considered and respected.

The raw materials of herbal chemical reference substances can be intermediates or the raw materials of the related herbal products as well as other appropriate sources.

Total synthesis should also be used for preparation.

In general, the raw materials should be consistent with the raw materials used for HMPs.

Alternative:

In order to provide appropriate reference materials, the necessary requirements, including those from standards or monographs for HMPs, are collected and evaluated in advance.

Appropriate extraction, separation, and purification methods should be selected according to the nature and type of the target compounds. A production of an appropriate number of batches of herbal chemical reference substances may be prepared to determine the process and parameters.

If necessary, measures of the produced batches should be taken for homogenization. Commonly used homogenization methods include dissolution, lyophilization, concentration, drying and mixing, or recrystallization.

A homogeneity test should be completed before qualification by testing, identification, assay and value assignment. Requirements for homogeneity assessment are specified in ISO Guide 35.

According to the properties of herbal chemical reference substances, the corresponding test items and the necessary limits should be stipulated based on the test results of appropriate numbers of batches of samples.

The test items may include, but are not limited to moisture, total ash, and solvent residue.

As for herbal chemical reference substances, necessary data and spectra or spectral data should be provided for the qualification of compounds with known structures and should be consistent with the values or spectra in the available literature.

If there is no record in the literature, sufficient data shall be provided, to confirm the physicochemical structure (if necessary including stereo structure) and the structural elucidation process should be provided.

The analytical data to be implemented are as follows:

— Ultraviolet spectrum.

— Infrared spectrum.

— Mass spectrum (if necessary).

— Nuclear magnetic resonance (if necessary).

— Melting or boiling point.

Additional data such as: elemental analysis, optical rotation, circular dichroism spectrum and X-ray single crystal diffraction should also be implemented.

The purity of herbal chemical reference substances established for assay purposes should be determined.

If possible purity values should be measured by certified testing or production laboratories.

Calculation of real content:

The equation shall be used to calculate the purity value of the herbal chemical reference substances.

Purity value = [100 % – (water content in % + content of residual solvents in % + content of inorganic impurity in %)] × chromatographic purity (%).

Moreover, other independent methods with different theories can be used additionally to verify the result, including differential scanning calorimetry (DSC).

The purity value is not necessary for the herbal chemical reference substances established for identification purposes.

Further studies should be conducted for the stability of herbal chemical reference substances, including influencing factors, long-term and accelerated stability studies. Packaging forms and materials should be considered to provide a basis for the valid stability period, storage conditions, and use precautions.

In order to ensure the stability of herbal chemical reference substances during their use, the developers should establish and implement procedures to ensure their long-term use reliability.

Herbal chemical reference substances should be continuously monitored with the analytical methods that have been used for the determination of the original data for product release.

For the assessment of the stability, the results should be compared with those obtained at the product release stage.

All operations should be performed in accordance with good operation practices (like GMP, GLP or other quality management systems) and documented to ensure traceability and integrity.

Traceability is one of the important attributes of reference substances, including the traceability of the establishment process of reference substances and the quantitative traceability of characteristic values. See ISO 17034, ISO GUIDE 35, and ISO/IEC 17025.

Herbal reference substances should have corresponding certificates of analysis to indicate their related attributes. The certificates of analysis should provide the following information:

Name, batch number, CAS Number, producer, general description (source, character, property value).

The labelling and instructions, if appropriate, should bear the name, batch number, CAS Number, preparation date, supplier, assigned values, storage conditions, filling amount, and use precautions. Additional information for specific products shall include: use without drying, drying before use (the temperature and pressure of drying), use after measuring moisture, use after direct dissolution, and use after extraction.

Herbal reference extracts or herbal chemical reference substances are used generally as originally packaged from producer according to international pharmacopoeias without changes in real content.

If herbal reference substances are toxic, they should be labelled with hazard symbols in accordance with ISO 3864-2.

Analysed and tested qualified herbal reference substances should be packaged in appropriate containers under appropriate conditions to ensure their integrity. Appropriate conditions should consider ambient temperature, humidity, oxygen content, and removal of static electricity. The herbal reference substances requiring special packaging may be packaged according to the results of studies on their chemical properties and stability. Containers may be reusable or disposable, but the latter is preferred to minimize the risk of decomposition, contamination, or water absorption. The filling amount of a single container should be determined according to the actual demand. If necessary, the compatibility of packaging materials and storage conditions should be investigated.

The storage conditions should be suitable for the requirements of the herbal reference substances, and conducive to the stability of properties and property values. Generally, it should be stored in a dark, dry, cool and clean environment. When special storage conditions are needed, special storage measures should be taken, which should be indicated in the label and instructions for use.

Appropriate packaging should be applied to minimize the risk of damage during transportation, keep the herbal reference substances at the appropriate temperature when necessary, and comply with current transportation regulations.

Bibliography

[1] ISO/FDIS 8284, Traditional Chinese medicine — Simplified accelerated stress simulation methods

[2] ISO Guide 31, Reference materials — Contents of certificates, labels and accompanying documentation

[3] ISO Guide 33, Reference materials — Good practice in using reference materials

[4] China Pharmacopoeia Commission. Pharmacopoeia of the People’s Republic of China, 2020

[5] European Pharmacopoeia Committee. European Pharmacopoeia (11th Edition), 2022

[6] Japanese Pharmacopoeia Committee. The Japanese Pharmacopoeia (18th Edition), 2021

[7] Ministry of Food and Drug Safety. The Korean Pharmacopoeia (12th Edition), 2019

[8] The United States Pharmacopieial Convention. The United States Pharmacopoeia, 2022