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Quality control methods
for herbal materials
Updated edition of Quality control methods for medicinal plant materials, 1998
WHO Library Cataloguing-in-Publication Data
Quality control methods for herbal materials.
Updated edition of Quality control methods for medicinal plant materials, 1998
1. Plants, Medicinal. 2. Medicine, Herbal. 3. Medicine, Traditional. 4. Quality control. 5. Manuals. I. World Health
ISBN 978 92 4 150073 9 (NLM classiﬁcation: QV 766) © World Health Organization 2011 All rights reserved. Publications of the World Health Organization can be obtained from WHO Press, World Health Organization, 20 Avenue Appia, 1211 Geneva 27 Switzerland (tel.: +41 22 791 3264; fax: +41 22 791 4857;
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Contents Contents Acknowledgment
Preface to the ﬁrst edition (1998)
Preface to the updated edition
Note to the reader
Powder ﬁneness and sieve size
General advice on sampling
Determination of foreign matter
Macroscopic and microscopic examination
Determination of ash
Determination of extractable matter
Determination of water and volatile matter
10. Determination of volatile oils
11. Determination of bitterness value
12. Determination of haemolytic activity
13. Determination of tannins
14. Determination of swelling index
15. Determination of foaming index
16. Determination of pesticide residues
17. Determination of arsenic and toxic metals
18. Determination of microorganisms
19. Determination of aﬂatoxins
20. Radioactive contamination
21. Culture media and strains used for microbiological analysis
22. Speciﬁcations for adsorbents for use in thin-layer chromatography........... 93
23. Reagents and solutions
Annex WHO good practices for pharmaceutical quality control laboratories
The World Health Organization wishes to express its appreciation for the generous ﬁnancial support provided by the Government of Japan for the publication of this document.
WHO acknowledges its indebtedness to approximately 260 reviewers, including members of the organization’s Expert Advisory Panel on Traditional Medicine and Expert Advisory Panel on the International Pharmacopoeia and Pharmaceutical Preparations, WHO collaborating centres for traditional medicine, and national regulatory authorities in over 114 countries who provided national information, comments and advice on the draft texts. The preparation of this document beneﬁted from technical support received from relevant professional bodies and nongovernmental organizations.
WHO also wishes to thank the members of the WHO Expert Committee on Speciﬁcations for Pharmaceutical Preparations, which met in 2004 and 2007 and held consultation meetings in 2005 and 2006, for their review of, technical guidance on, and endorsement of the updated contents of this publication.
The photograph on the front cover was kindly provided by Dr Yukihiro Goda, Head of the Division of Pharmacognosy, Phytochemistry and Narcotics, at the National Institute of Health Sciences, Ministry of Health, Labour and Welfare, Tokyo, Japan.
Plant materials are used throughout developed and developing countries as home remedies, over-the-counter drug products and raw materials for the pharmaceutical industry, and represent a substantial proportion of the global drug market. It is therefore essential to establish internationally recognized guidelines for assessing their quality. The World Health Assembly — in resolutions WHA31.33 (1978), WHA40.33 (1987) and WHA42.43 (1989) — has emphasized the need to ensure the quality of medicinal plant products by using modern control techniques and applying suitable standards. This manual describes a series of tests for assessing the quality of medicinal plant materials. The tests are designed primarily for use in national drug quality control laboratories in developing countries, and complement those described in The international pharmacopoeia,1 which provides quality speciﬁcations only for the few plant materials that are included in the WHO Model List of Essential Drugs.2 This manual does not constitute a herbal pharmacopoeia, but a collection of test procedures to support the development of national standards based on local market conditions, with due regard to existing national legislation and national and regional norms. Publications containing relevant speciﬁcations and standards, including those related to the food industry, are listed in the References and Bibliography.
The test methods described here are the best methods currently available. The manual will be revised as needed to incorporate improvements and additional tests and to reﬂect developments in work being carried out at national and regional levels, including projects aimed at ﬁnding replacements for toxic reagents.
In addition to the test methods, some suggestions regarding general limits for contaminants are included. They should be considered as a basis for establishing national limits. WHO is not currently able to recommend limits for contaminants since these are too diverse and there is a lack of consensus. For instance, the draft proposal for limits for some pesticides published in Pharmeuropa, 1993, 5(1): 19, is far more restrictive than that proposed here.
The test procedures cannot take account of all possible impurities. Common sense and good pharmaceutical practice should be applied in deciding whether an unusual substance not detectable by the prescribed tests can be tolerated.
The international pharmacopoeia, 3rd ed. Geneva, World Health Organization. Vol. 1: General methods of analysis, 1979. Vol. 2: Quality speciﬁcations, 1981. Vol. 3; Quality speciﬁcations, 1988. Vol. 4: Tests, methods, and general requirements. Quality speciﬁcations for pharmaceutical substances, excipients, and dosage forms, 1994.
The use of essential drugs. Eighth report of the WHO Expert Committee. Geneva, World Health Organization, 1998 (WHO Technical Report Series, No. 882).
viiQuality control methods for herbal materials
The analysis of medicinal plant materials is not restricted to those methods discussed or recommended here and many techniques similar to those used for the analysis of synthetic drugs are also frequently employed (e.g. volumetric analysis, gravimetric determinations, gas chromatography, column chromatography, highperformance liquid chromatography and spectrophotometric methods). Details of all these methods can be found in The international pharmacopoeia.
WHO published Quality control methods for medicinal plant materials in 1998, in order to support WHO Member States in establishing quality standards and speciﬁcations for herbal materials, within the overall context of quality assurance and control of herbal medicines. This publication came to be regarded as one of the key technical documents in ensuring and controlling the quality of herbal medicines.
At the end of 2007, the document WHO guidelines on assessing quality of herbal medicines with reference to contaminants and residues was published. These two publications were the result of joint activities between, among others, the teams of Quality and Safety: Medicines (QSM) and Traditional Medicine (TRM) within the WHO Cluster for Health Systems and Services.
The majority of adverse events reported in relation to the use of herbal products and herbal medicines are attributable to poor quality of the product. In order to promote the safety of herbal medicines, WHO has committed itself to develop the necessary new guidelines and to update existing ones relating to the quality assurance and control of herbal medicines.
The preparation of the guidelines relating to contaminants and residues gave WHO an opportunity to gather detailed technical information on various analytical methods for determining possible contaminants and residues in herbal medicines — including those described in 10 national and/or regional pharmacopoeias. Subsequently, WHO was able to compare each analytical method for speciﬁc contaminants and residues and could recommend methods for each of the possible contaminants and residues of herbal medicines. This material was identiﬁed to serve in updating the information and methods corresponding to sections 16–22 of Quality control methods for medicinal plant materials (1998).
As the Quality control methods for medicinal plant materials was widely distributed, WHO considered reprinting the publication. However, in view of the abovementioned opportunity given by the development of the guidelines, it was proposed to update the relevant sections and publish an updated edition instead of reprinting the existing publication. In 2004, the WHO Expert Committee on Speciﬁcation of Pharmaceutical Preparations agreed with this proposal.
Subsequently, draft chapters for the update were consolidated and were presented to the WHO Expert Committee on Speciﬁcations for Pharmaceutical Preparations at its consultation meetings and sessions in 2005 and 2006. At its 2007 session, the Expert Committee endorsed the publication of the updated edition.
The purpose of this updated edition remains unchanged from that of the ﬁrst edition. It is to support the development of national standards based on local market conditions, with due regard to existing national legislation and national
and regional norms. It describes a series of tests for assessing the quality of herbal materials, including the determination of pesticide residues, arsenic and toxic heavy metals, microorganisms and aﬂatoxins. This new edition will also serve as key technical training material in capacity-building training workshops in herbal medicines. Compilation of the updated edition of Quality control methods for medicinal plant materials — now with the updated title of Quality control methods for herbal materials — has been undertaken thanks to continued collaboration between QSM and TRM. This publication is an example of the immediate response of WHO in the implementation of the Global strategy and plan of action on public health, innovation and intellectual property that was adopted by the Sixty-ﬁrst World Health Assembly.
As this publication was being prepared, the WHO Expert Committee on Speciﬁcations for Pharmaceutical Preparations adopted WHO good practices for pharmaceutical quality control laboratories, which were published in 2010 as Annex 1 of the 44th report of the Committee. The scope of the good practice guidance in this annex includes pharmaceutical quality control laboratories handling herbal medicines. In order to promote these good practices and to provide general technical guidance in conducting the test methods described in this publication, Annex 1 of the Forty-fourth report of the WHO Expert Committee on speciﬁcations for pharmaceutical preparations is annexed to this publication for easy reference.
The test methods described in this publication are presented as examples of suitable methods for herbal materials.
The analysis of herbal medicines is not restricted to those methods discussed or recommended here. Other techniques are available.
When considering the choice of method, the level of detection and the herbal material matrix used for the testing (e.g. seeds containing oils) must be taken into account, and the method modiﬁed if required. The method of determination should be validated for the relevant matrix.
Although selected methods are described in detail in this document, they may not necessarily be the most modern or state-of-the-art methods. They offer some options and guidance but the available technology and resources, including human and ﬁnancial, may inﬂuence their use in particular countries.
In the event of limitations precluding the required analytical services for herbal materials in a particular district(s) in a country, it is recommended that at least other national or regional ofﬁcial laboratories should be available for such purposes.
The guidance of good practices for pharmaceutical control laboratories (see Annex 1), including quality assurance measures, should be followed when methods are chosen for all analyses. All methods chosen should be properly validated in accordance with these good practices.