Decoction is the earliest and most widely used dosage form in clinical application of traditional Chinese medicine. The decoction method has a history of more than 2000 years. The purpose of decoction is to transfer the active ingredients of the medicine into the decoction through physical and chemical actions such as dissolution, diffusion, permeation, and desorption. It is not as simple as adding water to boil the packets of Chinese herbs. There are some principles, methods, and conditions that need to be considered. Generally speaking, the following issues need attention:
Utensils The quality of Chinese herbal decoctions is closely related to the selection of decoction utensils. Sand pots are still preferred because the material of the sand pot is stable and does not react with the chemical components of the medicine. It also has uniform and gentle heat transfer, which is one of the reasons why it has been used since ancient times.
In addition, enamel pots, stainless steel pots, and glass containers can also be used. However, iron pots and copper pots should not be used mainly because their chemical properties are unstable. They may react with the chemical components contained in Chinese herbs. For example, they can generate ferric tannate with tannin components, insoluble polymers with flavonoid components, and salts with organic acid components. These will affect the quality of the decoction and directly relate to the clinical efficacy of Chinese herbal decoctions.
Water Nowadays, water such as tap water, well water, and spring water is commonly used for decoction. As long as the water is clean, it is acceptable. Tap water just needs to meet the national drinking water standards. If residual chlorine is a concern, letting the tap water sit in a container for a few hours before using it for decoction can significantly reduce the chlorine content.
Temperature Temperature is an important factor in extracting the active ingredients of Chinese herbs during decoction. Generally, low heat (simmering) is preferred for decoction. Starting with high heat can quickly coagulate the protein in plant-based herbs and affect the extraction of active ingredients. Therefore, it is best to soak the herbs in cold water for 15 minutes before decoction. This can allow the plant-based herbs to swell after soaking, and then use low heat to decoct them. This can slowly extract the protein without destroying the medicinal properties and prevent the water from evaporating quickly.
Time Different herbs have different cooking times. Generally, around 30 minutes is suitable. However, diaphoretic herbs and volatile herbs only need about 20 minutes (approximately 5 minutes after the water boils). For strong tonic herbs, the cooking time should be longer.
Many people are used to determining the cooking time based on the depth of color, thinking that the decoction is well-cooked only when the color of the decoction is the darkest. This is also incorrect because the color of some herbs can become darker the longer they are cooked, but the active ingredients of the herbs have already been extracted. Overcooking some herbs can cause the loss of certain volatile substances and the destruction of active ingredients.
Frequency Chinese herbal decoctions usually require two rounds of cooking (the liquid from the first round is called "head juice," and the liquid from the second round is called "second juice"). The amount of water for the head juice should cover the surface of the herbs, approximately 2-3 times the volume of the herbs. The amount of water for the second juice can be reduced appropriately. For some herbs that are difficult to extract active ingredients, such as mineral drugs and shellfish drugs, three rounds of cooking are required.
In addition, some drugs such as mineral quartz and cold water stone have low solubility in water, so they generally need to be cooked for a period of time before adding other drugs for decoction. Some drugs, such as diaphoretic herbs (mint, schizonepeta, etc.) or aromatic stomach-tonifying herbs (such as moschus, clove, etc.), should not be cooked for a long time. They should be added after other drugs have been cooked for a period of time (called "later addition") for decoction. Some valuable drugs such as rhinoceros horn and antelope horn need to be ground into powder for consumption, and drugs like Panax notoginseng and white powder need to be dissolved in water for consumption.
The above are just general precautions. It is also important to ask the doctor if there are any special requirements for decoction for your specific medication. Do not let the improper decoction affect the efficacy.
