With the modernization of traditional Chinese medicine (TCM), the forms of Chinese herbal medicine have evolved from traditional decoctions, pills, pastes, powders, and elixirs to modern forms such as tablets, granules, extracts, formula granules, and micro-powders. Chinese herbal decoctions have been developed over thousands of years and continue to be used today due to their flexible formulation, which allows for treatment based on the overall condition of the patient and syndrome differentiation, achieving precise treatment tailored to individuals. Additionally, using water as a solvent makes them affordable and accessible, especially effective for chronic diseases and difficult-to-treat conditions. Currently, many hospitals, pharmacies, and clinics offer decoction services to facilitate patient access, showcasing the unique characteristics of traditional Chinese medicine. Reports indicate that as of April 2015, Shanghai processed 8,660 prescriptions daily, with over 90% of medical institutions opting to outsource decoction services. However, outsourcing decoction raises quality control challenges, and the government should establish regulations and standards for outsourced decoction services.[1] The quality of Chinese herbal decoctions reflects the material basis of the formulas, which is crucial for clinical efficacy and patient health. Standardization can enhance the accuracy of clinical medication and consistency of efficacy.
The rapid development of Chinese herbal formula granules has garnered widespread attention. Chinese herbal formula granules (excluding shaped forms) are prepared using a process similar to that of traditional decoctions, maintaining a consistent composition of active ingredients, thus ensuring quality consistency between the two. Therefore, standardized decoctions can serve as a benchmark for evaluating the main production processes and quality control methods of formula granules.[2] This article primarily analyzes and discusses standardized decoctions in TCM, focusing on the selection of raw materials, preparation processes, testing indicators, and comparisons with Chinese herbal formula granules.
1 Concept of Standardized Decoctions
In August 2016, the National Pharmacopoeia Commission proposed the concept of “standardized decoctions” in the “Technical Requirements for Quality Control and Standard Setting of Chinese Herbal Formula Granules (Draft for Comments)” and in October 2017, the former State Food and Drug Administration introduced it in the “Simplified Registration and Approval Management Regulations for Classic Chinese Herbal Formulas (Draft for Comments)”. Standardized decoctions are defined as decoctions prepared according to standardized procedures under the guidance of TCM theory, involving solid-liquid separation and appropriate concentration methods for drying. They are based on the preparation methods recorded in ancient medical texts for classic formulas.[3] These two concepts are similar, with standardized decoctions serving as a reference. Other scholars have proposed the concept of standardized decoctions of Chinese herbal pieces, which are guided by TCM theory and based on clinical applications, prepared using modern extraction methods and standardized processes.[4] Japanese Kampo medicine has also introduced the concept of standardized decoctions for oral preparations, requiring the establishment of chemical and biological standards for standardized decoctions. Research data must be provided to ensure that the chemical composition and efficacy of the intermediate and final products are consistent with standardized decoctions.[5] The term “standard” in standardized decoctions primarily encompasses the source of herbal materials, uniformity of extraction processes, and rigor in quality control.
2 Quality Requirements for Chinese Herbal Materials in Standardized Decoctions
2.1 Source of Chinese Herbal Materials
“Good materials yield good medicine.” The quality of Chinese herbal materials, as the source of herbal pieces, is influenced by factors such as origin, soil quality, climate, growth duration, harvest season, cultivation techniques, genetic background, and variety, which largely determine the efficacy of Chinese herbal decoctions.[6] The herbal materials used in standardized decoctions should be representative and comply with the current version of the “Chinese Pharmacopoeia”. The varieties should cover the intended market regions and main production areas, with no less than three batches collected from each production area. A reasonable evaluation of representative samples should be conducted based on environmental conditions and quality levels, collecting at least 15 batches of herbal material samples, which should be legally processed into herbal pieces to prepare standardized decoctions. The ecological cultivation of Chinese herbs has certain regional, ecological, and safety characteristics, improving the quality of cultivated materials and ensuring clinical stability and efficacy, promoting ecological farming.[7]
2.2 Processing of Chinese Herbal Pieces
The “National Standard for Processing Chinese Herbal Pieces” and the “Chinese Pharmacopoeia” are the legally mandated standards for processing Chinese herbs, which should be followed. Due to the actual situation in China, some herbs that are widely used clinically have not yet been included in the current national standards and can be processed according to the provincial (municipal) standards for Chinese herbal pieces. The identification of processing has subjective factors; for example, the processing endpoint for toxic herbs like Ban Xia (Pinellia ternata), Chuan Wu (Aconitum carmichaelii), and Fu Zi (Aconitum carmichaelii) is often described as “a slight numbness on the tongue when tasted,” which involves significant human factors. Different individuals have varying sensitivities to odors, and prolonged operation can lead to olfactory fatigue, resulting in misjudgment of the processing endpoint.[8-9] Based on the significant research achievements in herbal pieces, standardized national standards for processing should be established to ensure the safety and efficacy of Chinese herbal products.
3 Development and Usage of Standardized Decoctions
Standardized decoctions are designed to meet clinical treatment needs and should not focus solely on the maximum solubility of indicator components but should closely align with clinical practices. Factors affecting the “standard” of decoctions, such as utensils, pre-treatment, soaking, water volume, and frequency, should be analyzed.
3.1 Preparation Methods for Standardized Decoctions Abroad
In Japan, the preparation method for “standardized decoctions” involves weighing an amount equivalent to the daily dose (approximately 20 g) of standard herbal materials, grinding them, adding 20 times the amount of water (approximately 400 mL), and decocting for at least 30 minutes, then concentrating to half the original volume (approximately 200 mL), and filtering while hot to obtain the standardized decoction.[10-11]
3.2 Preparation of Chinese Herbal Standardized Decoctions
For prescriptions written by doctors, after obtaining standardized herbal pieces, the decoction steps should be followed. Based on thorough research of ancient and modern literature, considering the properties, medicinal parts, and textures of the herbs, reference should be made to the “Management Norms for Chinese Herbal Decoction Rooms in Medical Institutions” issued by the Ministry of Health and the National Administration of Traditional Chinese Medicine (Document No. 2009, 3), which provides comprehensive references for pre-treatment methods, decoction frequency, water volume, decoction time, and other relevant parameters to prepare standardized decoctions.
3.2.1 Selection of Decoction Utensils The quality of Chinese herbal decoctions is closely related to the utensils used. Traditionally, clay pots and ceramic utensils are preferred due to their uniform and slow heat transfer, which minimizes chemical reactions. Iron utensils should be avoided, as they can easily react with tannin-containing herbs, causing side effects, and can impart a metallic taste to the decoction, leading to nausea and vomiting. Reports indicate that decoctions prepared using traditional methods yield better quality than those made with decoction machines.[12] The preferred utensils for decoction are clay pots and enamelware.
3.2.2 Pre-treatment Before Decoction Before decocting, the herbal pieces should meet the specifications for clinical decoctions. According to TCM dispensing principles, necessary treatments such as crushing, pre-boiling, and other methods should be standardized. The Japanese “standardized decoction” requires that herbal materials be crushed. The record in “Wen Bing Tiao Bian” regarding the use of Yin Qiao San states, “Crush to powder… when the aroma is strong, take it immediately, do not over-boil. Lung herbs should be light and clear; over-boiling will thicken the flavor and affect the middle jiao,” indicating that herbs should be crushed before use, and decoction time should not be excessively long.[13] Therefore, whether to crush the herbal materials requires further exploration.
3.2.3 Soaking Time and Water Volume for Decoction The water used for decoction should meet national health standards for drinking water. The herbs to be decocted should be soaked according to their texture, generally for no less than 30 minutes, but with no upper limit. Loose-textured herbs, such as flowers, leaves, and fine stems, can be soaked for 0.5 hours; hard herbs, such as tubers, roots, seeds, and fruits, should be soaked for 1 hour; and the soaking time for mineral, animal, and shell-based herbs can be extended appropriately. Care should be taken not to soak the herbs for too long to prevent spoilage, especially in summer.
When starting the decoction, the water volume should generally be sufficient to submerge the herbs by 2 to 5 cm. For herbs that require longer decoction times, additional water should be added as needed. A standardized soaking time and water volume should be established. Li Zhixing[14] reported a formula for controlling the water volume for decoction, stating that the first decoction water volume = total weight of all herbs in the prescription + 150 + dosage (the adult dosage is generally 150 to 300 mL), and the second decoction water volume = dosage + 200 (150 and 200 represent additional water volume).
3.2.4 Decoction Time and Quantity Each dose of herbs is generally decocted twice, with the two decoctions mixed and then divided. However, when using Da Huang (Rhubarb) for its purgative effect, it can be decocted once, as the first decoction promotes intestinal peristalsis, while the second decoction does not.[15] Special decoction frequencies for certain herbs should be listed.
Decoction time should be determined based on the properties, texture, and efficacy of the herbs. Generally, herbs should be boiled and then simmered for 20 to 30 minutes; for herbs that release exterior or clear heat, due to their volatile components, they should be boiled and then simmered for 15 to 20 minutes; for tonifying herbs, they should be boiled and then simmered slowly for 40 to 60 minutes. Generally, herbs are decocted twice, with the second decoction being slightly shorter than the first. During the decoction process, to ensure even cooking of the herbal pieces, stirring with a stick made of ceramic or stainless steel is recommended (the stick should be cleaned after stirring each herb).
Decoction quantity should be determined separately for children and adults. Each dose is generally divided into two equal parts or according to medical advice, with adults decocting to 400 to 600 mL and children to 100 to 300 mL.
3.3 Usage of Standardized Decoctions
Generally, it is advisable to take Chinese herbal medicine about 1 hour before meals, as the stomach will be empty, allowing for better absorption and quicker action at the site of illness. Herbs that irritate the gastrointestinal tract should be taken after meals; tonifying and nourishing herbs should be taken on an empty stomach for optimal absorption; sedative herbs should be taken before bedtime to aid sleep; and acute conditions may require frequent dosing without strict timing. Additionally, medication should be adjusted according to the patient’s condition.
4 Quality Control of Standardized Decoctions
4.1 General Quality Control
To ensure the overall stability and uniformity of standardized decoctions, a multi-component quality control model combining yield, transfer rate, indicator component quantity, and fingerprinting should be adopted.[16-17] The 2015 edition of the “Chinese Pharmacopoeia” specifies that the quality control of Dang Shen (Codonopsis pilosula) is based on the qualitative identification of Dang Shen saponins using thin-layer chromatography, combining chemical fingerprinting and quantitative determination of indicator components to identify 22 common peaks in the standardized decoction fingerprint, establishing the chemical profile and quality standards for standardized decoctions of Dang Shen.[18] Reasonable control limits should be established, and detection methods and limit indicators should be applied in the process quality control of “herb – herbal piece – decoction – extract or solid preparation” to ensure traceability and rationality of changes in material components during decoction preparation.[19] Acceptable ranges for yield, content limits, and similarity of final product fingerprinting should be determined, specifying relative retention times and peak area ratios. Similarity evaluation software should be used to generate reference fingerprints or characteristic maps for standardized decoctions, indicating the quality concentration of samples (equivalent to how many grams of herbal pieces per milliliter).
4.2 Quality Control of Volatile Components
Essential oils are important active components in some aromatic herbs, and losses during heating extraction are inevitable. The content of essential oils in standardized decoctions should be measured. It is recommended that herbal pieces with high essential oil content be separated into solution and essential oil, taking an appropriate amount of solution (without added essential oil), drying it, and then adding the essential oil to determine the quality.[20]
5 Comparison of Standardized Decoctions and Formula Granules
Chinese herbal formula granules represent an innovation in traditional Chinese medicine, made from single herbal pieces that comply with processing standards, extracted and refined using modern techniques into powder or granule forms. They have advantages such as being “clean, convenient, small, economical, precise, and stable”[21], eliminating the need for decoction, facilitating ease of use, rapid onset, advanced processing, ease of storage, and convenient quality control, aligning with modern societal demands for medications.[22] Compared to formula granules, standardized decoctions do not have interference from excipients or drying processes, maintaining consistency with traditional clinical decoctions, and allowing for the achievement of various ideal concentrations through the combination of herbal pieces or extracts.[4] Fingerprinting serves as the basis for quality control of Chinese herbal formula granules, ensuring that under conditions of consistent raw materials, processes, and specifications, standardized fingerprints are established to effectively control quality stability.[23] Standardized decoctions serve as reference formulations for the secondary development of Chinese patent medicines, and Chinese herbal formula granules can use this as a “benchmark” to evaluate the rationality of the main production processes and quality control methods.
6 Outlook
Standardized decoctions in TCM are guided by TCM theory and based on clinical applications, prepared using modern extraction methods and standardized processes, including single herbal pieces and classic formulas. The National Pharmacopoeia Commission regards standardized decoctions as reference standards to measure the consistency of Chinese herbal formula granules with clinical decoctions, thus also serving to assess the consistency of other forms of herbal pieces with clinical decoctions.[24] This article analyzes factors affecting standardized decoctions, including decoction utensils, sources of herbs, processing, decoction, quality control, and efficacy, aiming for close collaboration among disciplines such as botany, processing, pharmacy, pharmacology, and clinical practice. The lack of unified standards for processing, soaking time, water volume, and decoction time is critical for the extraction of effective components from herbs and the realization of clinical efficacy, necessitating the establishment of standardized regulations.
By optimizing each link, the prepared “standardized decoction” can closely resemble the material basis of clinical decoctions, improving the intrinsic quality of the product and ensuring clinical efficacy, making it worthwhile to promote the application of standardized decoctions in the development of single or compound preparations. The purpose of proposing “standardized decoctions” is to ensure clinical efficacy. Scholars have established preparation and quality standards for standardized decoctions of herbs such as Dan Shen (Salvia miltiorrhiza), Ma Huang (Ephedra sinica), Long Dan (Gentiana scabra), and Hong Hua (Carthamus tinctorius), which can provide foundational data support for the standardization and industrial production of formula granules. However, the decoctions that patients take clinically vary with the syndrome, and the quality control indicators of complex formulas will also undergo complex changes. Therefore, it is essential to examine the most fundamental aspects of herbal material selection, processing, preparation processes, and quality control to ensure that the decoctions produced are close to standardized decoctions. Only by genuinely valuing clinical practice and discovering truths from practice can we pose and solve problems.
References (omitted)
Source: Li Yan, Bai Ming, Song Yagang, Guo Hui, Miao Mingsan. Research and Reflections on Standardized Decoctions in Traditional Chinese Medicine [J]. Chinese Herbal Medicine, 2018, 49(17):3977-3980.
