Understanding herbal preparations

The `why' and `how' of choosing standardized botanicals.

Over-the-counter herbal preparations are available in several different forms: bulk herbs; teas; tinctures; fluid extracts; and tablets or capsules. It is important for all of us to understand the differences among these forms, as well as the methods of expressing strengths of herbal products.

Let's look at the benefits of standardized botanical extracts and the importance of delivering a clinically effective level of active compounds, regardless of the form of the herbal preparation.

An extract defined

One of the major developments in the herb industry involves improvements in extraction and concentration processes. An extract is defined as a concentrated form of the herb obtained by mixing the crude herb or root with an appropriate solvent (such as alcohol and/or water).

What's in a form?

Teas/infusions. When an herbal "tea bag" is steeped in hot water, it is actually a type of herbal extract known as an infusion. The water is serving as a solvent in removing some of the medicinal properties from the herb. Teas often are better sources of bioavailable compounds than is the powdered herb, but are relatively weak in action compared to tinctures, fluid extracts, and solid extracts.

Tinctures. Tinctures are made using an alcohol and water mixture as the solvent. The herb is soaked in the alcoholic solution for a specified amount of time, depending on the herb. The solution is then pressed out yielding the tincture.

Fluid extracts. Fluid extracts are more concentrated than tinctures. They are made by using either lower initial quantities of alcohol or by distilling off some of the alcohol, typically by using methods that do not require elevated temperatures, such as vacuum distillation and counter-current filtration. However, some small manufacturers produce fluid extracts in a similar manner to tinctures via a cold-percolation process.

Dry-powdered extracts. A dry-powdered extract is produced by further concentration of the extract by the mechanisms described above for fluid extracts. The solvent is completely removed and then the extract is usually ground into course granules or a fine powder.

Typically, one gram of a dry-powdered extract is equivalent to at least 4 ml of a fluid extract (1/7th of an ounce) and 40 ml of a tincture (almost 1 1/2 ounces).

Determining potency and quality

In the past, the quality of the extract produced was often difficult to determine, since many of the active principles of the herbs were unknown. However, recent advances in extraction processes, along with improved analytical methods, have reduced this problem of quality control.

Standardized extracts are guaranteed to contain a "standardized" level of active compounds or key biological markers. Stating the content of key, active marker compounds, such as the percentage of kavalactones (in kava), allows for more accurate dosages to be made.

Although referred to in terms of active constituents, it must be kept in mind that these are still crude extracts and not isolated constituents. For example, the St. John's wort extract standardized for its hypericin content at 0.3 percent contains a very high percentage (99.5 percent) of other compounds found in St. John's wort. The hypericin content simply reflects a marker for quality and dosage.

The bottom line

The effectiveness of any herb or herbal product is dependent upon providing an effective level of active compounds.

Regardless of the form of the herbal preparation, clinical effectiveness requires delivery of an active dosage. Because of this irrefutable fact, standardization for the level of active components or key biological markers is the only real assurance to the delivery of an effective dosage.

Michael T. Murray, N.D., is widely regarded as one of the world's leading authorities on natural medicine. He is a graduate, faculty member, and serves on the Board of Trustees of Bastyr University in Seattle, Wash. In addition to maintaining a private medical practice, Dr. Murray is a noted writer, educator, and lecturer. He is currently the editor of the Natural Medicine Journal. Visit Dr. Murray's website at: www.doctormurray.com.

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