Therefore the objectives of this review is to summarize and discuss the differences between the TCM monographs in EP 10th edition (data updated to supplement 10.2, published in January, 2020) and ChP 2020 edition to emphasize the state of TCM monographs in the EP. Note that TCM in this review refer to the 73 herbal drugs considered as TCM in both pharmacopoeias in order to avoid confusions, other examples out of the 73 TCM are given as herbal drugs in general. Furthermore, some advanced analytical techniques for quality standard of herbal drugs and TCM are also discussed to show the progress of TCM quality control.
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In addition, Latin synonyms in pharmacopoeias could be an issue for identification of botanical origins of TCM. An analysis showed that at least 16.13% Latin names of TCM in ChP (2010 edition) were not in accordance with Flora of China and the reasons of the issue may include: repeat naming of the same species; synonyms of the families; new definitions of species and families; as well as traditional use of old Latin names [16]. Among the 73 TCM reviewed, 24 entries have Latin synonyms stated in EP, and some other TCM without annotation may also have Latin synonyms. For example, botanical origins of Sinomenii Caulis in ChP include Sinomenium acutum (Thunb.) Rehd. et Wils. or Sinomenium acutum (Thunb.) Rehd. et Wils. var. cinereum Rehd. et Wils. But in fact, the latter is synonym of the former, and the former is the botanical origin stated in EP, thus the botanical origin of Sinomenii Caulis in both pharmacopoeias is actually the same. Therefore, when determining the botanical origins of TCM, Latin synonyms is still an issue that should be addressed.
In the application of TCM, herbs could be applied either as in whole plant, or as in different parts of the plant such as aerial parts, underground parts, root, rhizome, stem, bark, leaf or flower. Furthermore, active constituents and harmful constituents may be varied in different parts of an herb. Therefore, it is very important to specify the medicinal parts in quality standard of TCM. By comparing the stated medicinal parts of TCM between the two pharmacopoeias, most are the same except few such as Ephedrae Herba and Sanguisorbae Radix (Table 1). But the differences in these TCM are small, such as underground parts instead of root, thus little or no influence would be generated under the circumstances.
The above examples imply that it is important to specify the botanical source and the medicinal part of a TCM, because substantial differences may occur in the components and pharmacological effects when the wrong plant or medicinal parts are applied. However, the origin of herbal drugs and TCM stated in pharmacopoeias may be more or less influenced by the species available and the application habit in the region. Therefore, extensive research are required to show that if those differences could be compatible with each other and whether substitution is possible for one to another.
In quality control of TCM, since the composition and pharmacological effects of TCM are usually very complicated, single component, multiple components or even the global chemical profile with many components may be utilized to assess the quality of a specific TCM. Chemical reference substance (CRS) and herbal reference substance (HRS) in EP or CRS, reference extract and reference crude drug in ChP could be used as reference standards for TCM identification and compound quantification. Therefore, choosing the appropriate marker is very important for accurate and valid quality assessment of TCM, especially when active markers are not available in analysis. By comparing the markers used in both pharmacopoeias, interesting differences are observed. Of the TCM reviewed, besides different choices of active markers in analysis, EP has included many analytical markers, which serve solely for analytical purposes and irrespective of any pharmacological or therapeutic activity, in TCM identification and quantification. For example, aescin and arbutin are used as analytical makers for TLC identification of Anemarrhenae Asphodeloides Rhizoma and Notoginseng Radix; caffeine is used as reference for the determination of pinoresinol diglucoside in Eucommiae Cortex. While ChP has included many reference crude drugs in TCM identification. Among the 73 TCM reviewed, 37 in ChP employ reference extract or reference drug in TCM identification, and 12 of them include only reference drug in monographs for TLC identification. In addition, EP has included many specific references for system suitability assessment, while ChP uses the intensity markers or active markers in TCM identification or assay for this purpose. For example, in EP, isoeugenol and methyleugenol are used for the system suitability test of TLC identification of Ophiopogonis Radix. Propyl parahydroxybenzoate and saikosaponin A are employed for the system suitability of LC quantification for Bupleuri Radix. Moreover, 20 out of 73 TCM apply HRS in system suitability assessment of LC assay. From the above, it is shown that other than active markers, analytical markers and HRS or reference drug are also applied in monographs either as substitution of active markers or for method validation and system suitability assessment etc., so they are important alternates when active markers are not available or with high costs.
For some herbal medicines other than the 73 TCM discussed above, even though they share the same botanical source between the pharmacopoeias, they are considered to be traditional European herbal drugs instead of TCM as mentioned at the beginning of this review. Those herbal drugs including Ginseng Radix, Liquiritiae Radix and Rhei Radix etc. has also been well known and frequently applied in herbal remedies of China. By comparing the monographs of these herbal drugs to TCM monographs, some similarities and differences are found. Although these herbal drugs may have at least one identical botanical source in the two pharmacopoeias, inclusion of other species into the monographs are also frequently happened in ChP and sometimes in EP. Also, although the medicinal parts stated in the monographs are similar, small differences (e.g. aerial parts instead of whole plant) may be occurred. The general requirements of these herbal drugs are similar to TCM, but quality control methods may be significantly different between the two pharmacopoeias since the monographs of these herbal drugs are not drafted by Working Party on TCM, and are not on the basis of ChP. For example, for Rhei Radix, there is a chemical identification test included in EP, which is not included in ChP; while for Aloe, the chemical identification method is included in ChP but not in EP. Furthermore, different assay methods may be applied for these herbal drugs including Aloes, Caryophylli Flos, Lini Semen, Rhei Radix, etc. (Table 4 and Fig. 1). The differences in the monographs of these herbal medicines between the two pharmacopoeias may be mainly originated from the different applications and indications between Europe and China. For example, according to European Medicines Agency, Curcumae Longae Rhizoma in Europe is mainly used for gastrointestinal disorders such as feelings of fullness, slow digestion and flatulence, but in ChP it is used for the relief of pain. The above illustration implies that, quality control of herbal drugs is relevant not only to the chemical compositions but also the application habits in the region. Therefore, it is important that quality control should meet the actual application of herbal drugs in daily life in order to protect the benefits and safety of consumers.
It is known that the efficacy of TCM is contributed by their multi-components or in their combinations. Thus multi-components determination has been commonly accepted as the effective way for the quality control of TCM. But the major obstacles of the approach are the lack of commercial available CRS and the high costs involved. In order to resolve the problem, QAMS method that could accurately determine the contents of multiple constituents by using a single compound has been proposed. It uses a commercially available and cheap CRS as the internal standard, then the peaks of other compounds could be identified by relative retention time and the contents could be calculated by the validated relative correction factor [63]. QAMS method has been adopted in several monographs in both pharmacopoeias, such as Andrographis Herba, Aucklandiae Radix and Evodiae Fructus in EP, as well as Andrographis Herba, Coptidis Rhizoma and Salviae Miltiorrhizae Radix et Rhizoma in ChP. It has also been widely used for multi-components quantification of TCM, including Scutellariae Radix [64], Astragali Radix [65], Gastrodiae Rhizoma [66], etc. QAMS is a simple and practical method for simultaneous determination of multi-components in herbal drugs, which is expected to be utilized more widely by pharmacopoeias in the future.
In summary, quality control of TCM is very important in TCM application and the complexity of TCM promotes difficulties in quality control and quality standards establishment for TCM. But even so, working parties in EP and ChP have managed to assess TCM quality by regulating the origins, identification, quality parameters (such as moisture content and impurities) and active components contents in TCM. However, there are differences between the pharmacopoeias in Europe and China, including the source of TCM herbs, tests required for TCM, marker selection and assay methods etc. because of the different systems in quality control of TCM, and the application habits of TCM between Europe and China. Nevertheless, improvements may be made in the pharmacopoeias from the experience of the two parties. For example, although ChP (2020 edition) has removed the TCM containing aristolochic acids including Aristolochiae Herba and Aristolochiae Fructus, there are some TCM easily confused with the herbal drugs from Aristolochia species, such as Akebia Stem, Aucklandiae Radix, Clematidis Armandii Caulis, Stephaniae Tetrandrae Radix and Sinomenii Caulis. Including the test for aristolochic acids in these TCM as EP may be necessary and important to avoid the adulteration or misuse of aristolochic acids-containing drugs. On the other hand, in EP, HRS has been used for system suitability assessment of LC assay, it may be utilized for TLC identification as well, specially for the TCM without suitable active markers or lack of commercial available CRS. EP may also include methods of molecular identification and standards for residue of sulfur dioxide for more comprehensive quality control of TCM. Therefore, discussion about these issues and cooperation between different parties are urgently needed to improve and harmonize the quality standard of TCM. With the development in analytical techniques and quality control methods such as improvements in chromatography techniques as well as the application of molecular identification, new quality control measures are very likely to be used in the future for better quality assessment of herbal drugs. 2ff7e9595c
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