Quality of Herbal Products

February 2000; Volume 2: 12-13

By Tieraona Low Dog, MD

Practitioners and consumers are uncertain about which criteria to use in comparing the quality of different herbal products. The few people who really know which criteria to apply are those who are actively involved in product manufacture and often provide information that is "biased" in favor of their own procedures. This makes objective comparison for the herbal practitioner very difficult: It often becomes a case of "Whom do I believe?" The following questions should be considered when discussing the quality of herbs:

Have we been sold the correct species?

To answer any of these questions, a certificate of analysis is required. Any certificate must name the plant species and then justify the accurate naming of the species with the following information: microscopic appearance, odor, taste, microanalysis (including thin layer chromatography), and knowledge of the collection location.

Is the herb clean?

Testing an herb’s cleanliness will give an overall picture of purity and quality, and will provide information regarding soil contamination and contamination from other organic sources, including the less desirable parts of the same plant. This is most commonly done by testing for the total ash and acid insoluble ash content.

Is the sample pure? Do we have the correct part of the plant? Is there any contamination?

Macroscopic and microscopic tests give a good indication as to the sample’s purity. One can usually see overt contamination from other plant material and from the less desirable part of the same plant. A small level of contamination with non-specific organic matter (less than 2%) is allowable.

Has the plant been harvested at the correct time?

For example, roots should be collected in the autumn or early spring when sugars, nutrients, etc. have descended back into or not started to rise from the root. The test which most closely correlates to this question determines the water soluble extractive content of the herb.

Has the company used sound extraction techniques to obtain the full range of active constituents?

Herbal products should be standardized to ensure that they are high quality and contain a consistent level of the therapeutically active plant constituent. (See Alternative Therapies in Women’s Health, July 1999, pp. 57-59.)

Have any known markers been assayed?

In a significant number of cases, it is desirable to know the levels of certain active constituents—the tropane or berberine alkaloids for example. This allows us to achieve safe therapeutic doses and avoid potential problems of toxicity.

Has the herb been sufficiently dried and well prepared?

Appearances can be deceiving. A dried herb should contain a total yeast and mold count of less than 100 organisms/g. Figures of 10,000 organisms/g are commonplace, and this often correlates with a high moisture content.

Is the herb organic, collected in the wild, or commercially cultivated?

Clearly we should avoid commercially cultivated products where spraying has been employed. However, there is no available evidence to suggest that one technique regularly yields products with lower pesticide residues than another since contamination is possible on any crop or wild area due to water- or wind-borne pollution.

Has a microbiological assay been performed?

Microbiological assays are becoming more and more important as legislation worldwide tightens with regard to herbal remedies. Limits that have already been set in Europe include total viable count, total number of live microorganisms, total yeast and molds, coliform count, E. coli, and Salmonella.

Have pesticide residues been checked?

For the most part, pesticide analyses are not routinely undertaken except in those cases where specific problems are known to exist. Isolated problems do occur, however, and these tend to be country specific. With the gradual increase in medicinal herb cultivation it will be interesting to see if this potential problem worsens.

Do I trust the information and documentation (if any) provided?

Different individuals place emphasis on different areas. For some, it may be more important that an herb is organic rather than tested by a specific active assay, while for others precisely the opposite is true. Unfortunately, to find both is a rarity.