Making Decisions About Herbal Therapies: How Herbal Therapies Are Prepared
Part of A Practical Guide to Herbal Therapies for People Living With HIV
Herbal medicines can be purchased in several forms, any of which may be appropriate, depending on the intended use. Herbal products usually contain a variety of biochemicals found naturally in plants. Many different biochemicals contribute to a plant's medicinal benefit. Chemicals known to have medicinal benefits are called active ingredients. The terms primary and secondary ingredients are sometimes used to indicate the relative importance of each biochemical constituent.
The way an herb is prepared may effect how much of each active ingredient is in the product. The time and season of harvest, as well as the type of soil in which it grows, will also affect the potency of an herb.
Therapies are generally prepared by grinding the parts of the plant that are used medicinally. This ground plant matter is called the macerate. Depending on the type of plant and the process used, the macerate may be dried before it's ground. The macerate is then soaked in liquids used to extract the active ingredients from the plant. These liquids are called menstrua, and this process is done in several different ways.
Macerate - usually dried leaves or flowers
Infusions are created by pouring boiling or near boiling water on the dried macerate. A tea is probably the most common type of infusion. Infusions may be left to sit covered from a few minutes to several hours, depending on the herb used and the desired strength. Creating an infusion may be the most useful way to prepare a powerful herb when only a modest effect is desired. For example, you might use this method to create a strong herbal laxative.
Macerate -- usually roots and bark
Decoctions are made by combining the macerate and menstruum at room temperature. The mixture is then heated gently or boiled for varying lengths of time. On the one hand, decoctions are not appropriate in cases where heat destroys the active ingredients. On the other hand, heat may enhance the effect of some active ingredients. Microwaves are not appropriate for this process.
Macerate -- any ground plant material
Tinctures are made by soaking the macerate in the menstrua and then pressing it to remove the liquid. Menstrua containing combinations of substances remove the active ingredients from the macerate more effectively than water alone. The preparation process may be enhanced by letting the mixture sit for a longer period or by exposing it to sunlight or heat. Although tinctures are more powerful than infusions or decoctions, their strengths can vary. The strength of a tincture is usually indicated by the ratio of macerate to menstruum.
Extracts (Liquid and Solid)
Macerate -- any ground plant material
Although extracts are similar to tinctures, they are more concentrated, because the alcohol (or other solvent) is removed by distillation, a process that may or may not involve heat. Liquid extracts have been distilled to the point at which most of the alcohol has been removed. Solid extracts have been distilled to the point at which all fluids are gone.
The label of an herbal therapy will usually indicate which of these methods was used to prepare the product and may also reveal the relative amounts of macerate and menstruum used. This information is usually expressed in the form of a ratio. For example, if an extract is labelled 4:1, it means that four kilograms of plant material were soaked in one kilogram of fluid, or it means that the extract has been concentrated fourfold.
The labels of certain herbal products indicate that the product's content has been standardized to contain a particular amount of a specified biochemical constituent. For example, the silymarin content of milk thistle is often standardized to 80 per cent. In some cases, the specified biochemical is one of the primary active ingredients, or it may simply be a "marker" that is easy to measure. Standardization gives the buyer a measure of potency by which to judge the quality of the product and to compare dosage to that of clinical trials. It also helps ensure that the manufacturer has used the correct herb. Unfortunately, since the amount of other active ingredients can vary according to the growing season, knowing the quantity of one biochemical does not necessarily mean that all the active ingredients are present in adequate doses. Some herbalists are in fact concerned that the widespread use of standardization may actually compromise the quality of herbal products and ensure that the herbal market becomes more dominated by pharmaceutical companies. For an excellent summary of this viewpoint, see Michael Tierra's article "Why Standardize Herbal Extracts?" posted on the Planet Herbs Web site at www.planetherbs.com. It should also be noted that some manufacturers now use the term standardized very loosely to mean only that the product has been prepared for market in some standard way.
This article was provided by Canadian AIDS Treatment Information Exchange. Visit CATIE's Web site to find out more about their activities, publications and services.