The increasingly important area of quality control as it relates to herbal products begins with the ability to accurately determine the botanical identity of any given plant material. Over the past several decades the herb industry has developed sophisticated and complex chemical assays to identify specific marker compounds in plant materials to help ensure identity and/or qualitative aspects for the proposed botanical preparation. However, these assays have not always been based on botanical references, leaving the true identity of specific plant materials in question. The fundamental baseline for quality control of herbs is the ability to ascertain botanical identity by making reference to plants that have been verified by competent botanical authorities as being correctly classified, according to the universally-adopted system for the classification and nomenclature of plants.

In his 2-volume work, Species Plantarum, published in 1753, Swedish botanist Carl von Linne, also known as Carolus Linnaeus (1707-1778), the grandfather of biological taxonomy, provided a sophisticated universal structure that offers a system to identify and name plants. Linnaeus wrote the polynomials (multi-names, often three or more per plant) of all plants described up to that time and shortened them to the binomial (two-name) system universally applied in science today.^1,2 In this system the family, genus, and species of a plant are based on the morphology of the flower, i.e., the plant’s sexual characteristics. These identifications serve as a foundation for traditional botany, providing a common language for scientifically trained professionals from any culture, speaking any native language, the means to investigate the plants of the world and exchange information about them. The use of this formal framework crosses many related botanical disciplines. For example, taxonomy, medical botany, horticulture, agriculture, ecology, and ethnobotany all use the botanical binomial system of Linnaeus to communicate.

The herb and natural products industries are the places where numerous scientific disciplines combine with business. The array of experts in the natural products industry includes botanists, ethnobotanists, medical botanists (also called herbalists), pharmacognosists, natural products chemists, biologists, health professionals (e.g., medical doctors, naturopaths, acupuncturists, and frequently chiropractors), and others. All these disciplines overlap within the research and development of herbal products. Now, with impending and increasing government regulations that define good manufacturing practices (GMPs) for herbal dietary supplements, the application of many of these disciplines joined with good research practices will become standard operating procedure for product development and manufacturing activities. This confluence emphasizes that the science of botany is the foundation of the herbal industry. Botany becomes the focal element in what is now required to ensure the sustainability of a truly multidisciplinary industry.

The Value of an In-house Herbarium

Curiously and ironically, there has long been a paucity of applied botany in the botanical industry. In the middle 1980s the first author of this paper established one of the first in-house herbaria in the American herb and natural products industry at the Celestial Seasonings R&D Lab. An herbarium is a collection of pressed plant species, with each individual plant mounted on acid-free paper designated for archival use. The herbarium sample usually contains all parts of the plant, but particularly the flower to confirm proper identification. (The Linnean system of classification is based on, but not limited to, the sexual characteristics of the plant, i.e., its flowers.) Herbarium specimens are usually stored in specially built cabinets under controlled conditions to help ensure long-term survival of the samples.

The Celestial Seasonings herbarium consisted of two cabinets. One cabinet contained a set of pressed herbarium specimens of economically important plants used in the teas that the company produced; this cabinet also contained a set of plants that were either toxic or for other reasons undesirable for use in the teas. The second cabinet collection included seeds from plants in the growing region from which a particular specimen was obtained, miscellaneous plants mistakenly collected in the same harvest session, inappropriate plant parts collected during the cleaning of the desired plant, and plant samples for use in future products.

These various reference materials are known as voucher specimens. They provide direct linkage via a paper trail from the field, through the purchasing department, to the research and development department, on to the manufacturing department, and finally to the finished product. The oldest collections of plant vouchers were made 300 years ago and compiled as books, which were held by botanists or stored in the libraries of monasteries and wealthy patrons. Joseph Banks (1743-1820), the originator of the extensive herbarium collections located at the Royal Botanic Gardens in Kew, England, provided most of these first specimens from his various expeditions, particularly those with Capt. James Cook to the South Pacific. Banks’ collections are now housed in the herbarium at the Linnean Society in London. These collections were expanded with the establishment of herbaria in the sixteenth and seventeenth centuries at universities in Bologna (1570), Basel (1588), Oxford (1621), and at the Naturkundmuseum in Kassel, Germany (after 1569).³ All plants used in health products during that period were deposited as archival records into herbaria (i.e., libraries of plant specimens) and eventually many became known by their Latin species name officinale or officinalis, designating their being the true species officially recognized in various pharmacopeias.

Thus, the practice of obtaining and maintaining reference voucher specimens is centuries old. Voucher specimens have many uses. They serve as a basis for confirmatory macroscopic tests on incoming plant materials and if any potential product liability issues arise they can ensure the proper identity of a plant in a commercial product. These reference materials were used most frequently at Celestial Seasonings by milling and cleaning personnel to help qualify the identity and cleanliness of incoming botanical materials, preventing contaminations.

An example of the benefit of this collection occurred when there was an adulteration of Eastern European comfrey (Symphytum officinale L., Boraginaceae) leaf with deadly night shade (Atropa belladonna L., Solanaceae) leaf. The lab personnel were able to review the archival specimens to verify that the samples macroscopically viewed in the research and development (R&D) department were, in fact, comfrey.

Another example was the discovery of the highly toxic castor bean seeds (Ricinus communis L., Euphorbiaceae) and precatory bean seeds (Abrus precatorius L., Fabaceae) found in cultivated and wild-harvested materials. The processing personnel, trained by the R&D department personnel with samples from the herbarium, prevented large-scale contaminations of the commercial product, potential adverse effects on the company’s tea customers, and potential product liability issues.

All research protocols, whether chemical, biological, or botanical, are based on reference substances. Without a protocol that includes the use of reference substances, the results of the work cannot be considered scientifically valid or accurate. What then are the necessary reference substances for botanical research protocols?

Botanical Reference Materials

Reference substances are the “knowns” used in processes and protocols throughout research and manufacturing. These substances must be well characterized in order to be useful in their application. Methods published by various official and unofficial compendia and by standard-setting organizations or indeed any authoritative source, must employ such substances. Organizations that establish such standards include the American Herbal Pharmacopoeia (AHP), the Association of Official Analytical Chemists (AOAC), Association of Systematics Collections, the European Pharmacopoeia (EP), the United States Pharmacopoeia (USP), and the World Health Organization (WHO). Botanical reference substances must also be used in chemical testing of botanical materials, e.g., thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC) and related chemical analytical methods (see the chemical references article on page 38of this issue), biological assays, microscopy, and of course, in botanical evaluation and determination at a macroscopic level.

The voucher specimen is considered the “gold standard” of botanical reference materials. A voucher specimen is a reference sheet and a tool used by specialists to properly identify whole plants and plant parts. It provides documentation for the scientific identification of ethnobiological materials.⁴ The pressed whole plant is permanently mounted on archival materials. One key consideration is that the vouchered material must be representative of the plant population being studied. The labels include specific site information for re-collections. The Latin binomial is annotated or verified by specialists in the field of botany, particularly taxonomy (the discipline involving the classification and naming of plants). These specialists have usually studied either a specific geographic region or a specific family of plants. Commonly, these botanical specialists have authored papers published in peer-reviewed journals and are often known internationally within the community of taxonomists.

Botanical voucher specimens are plants collected at flowering times and/or during the harvest. These reference materials, therefore, can be used to confirm, without ambiguity, the identity of the plant described or named by the user. When the plant is harvested in a sterile or non-flowering time, these reference materials are not as definitive, unless they refer to a fertile voucher of the same population or are accompanied by bulk materials that have been fully characterized through microscopic examination and chemical tests employing suitable botanical and chemical reference standards complementing their identity. Materials to confirm identity by these tests can be scavenged or removed from herbaria sheets when bulk excess is not available. Bulk materials that have been characterized by chemical methods exclusively cannot be considered “authenticated.” Authenticated specimens are those that have a direct link to the vouchered, annotated, pressed flowering specimen, except as stated above, where they have been fully characterized through both microscopic and chemical testing based on a botanical reference.

Why are botanical voucher specimens necessary reference materials? All “good science” is based on the use of “knowns” (reference substances) and then testing a hypothesis using these references to understand the differences and similarities. While this can be a very creative process, the results of good science are always confirmed by the use of reference substances and previous discoveries. If reference substances are not part of a research protocol, the results do not employ the rigid parameters of science and, lacking scientific validity, can be erroneous in their findings. Voucher specimens are one such reference substance necessary to attain the scientific validity that the herb and natural products industry needs. Thus, a “characterized” bulk herb may not be based on a known standard or reference. In the professional view of these authors, based on many years of combined experience in quality control and good manufacturing practice (GMP) activities in the botanical industry, the use of validated chemical analytical methods to assist in the botanical identification of a sample, apply only when the chemical references are directly linked to an annotated, herbarium voucher specimen. It can then be called “authenticated” material.

One of the primary challenges the herb and natural products industry faces today is from reporting in the media, which appears to delight in criticizing and undermining every aspect of industry practice. Implementing the application of vouchers with tracking measures may reduce contamination and some of the safety concerns and occasional adverse reactions due to misidentification, and consequently, reduce some of the adverse publicity that is seen so frequently. The application of vouchers and other reference substances in the natural products industry thus provides a means to assure consumers, health professionals, and others that the plants used in herbal products are accurately identified, legitimate, and reliable.

The first step, then, is to have reference substances and test methods available and in place. Nonprofit groups like AHP and USP, and private consultancies like Botanical Liaisons, LLC, and others, have focused on providing these references materials and methods during the last few years. Unfortunately, progress has been slow and industry support for these efforts has been lacking.

New GMPs for Botanical Dietary Supplements

The FDA is now forcing the issue regarding the use of voucher specimens through its issuance of the recently proposed GMPs,⁵ the publication of final rules which are believed to be forthcoming by the end of this year (2004). This regulation will govern the manufacturing processes in the dietary supplement industry. The following are some excerpts from the proposed GMPs (also referred to as cGMPs, or current good manufacturing practices) that relate to botanical standards:

Dietary ingredient identification is an important part of cGMPs. . .[and] identity testing requirements are needed but . . . no single approach or test method may be appropriate for every dietary ingredient. . .[T]he key principle in dietary ingredient identification testing is to establish an appropriate procedure that will identify, with certainty, the dietary ingredients usedin making a dietary supplement. [emphasis added]. . . The manufacturer must conduct identity tests to ensure that they used the correct ingredient to prevent potential serious adverse events. [page 12169]⁵

This discussion comes under the heading of FDA’s focused mandate that the forthcoming GMPs for dietary supplements assure that these products meet specifications for “identity, purity, quality, strength and composition.” [page 12158].⁵ Additional excerpts from FDA’s Proposed Rule on GMPs emphasize the importance of using reference materials for botanical identity. FDA presents some detail in its discussion of botanical identification:

When sufficient morphological characters are present to separate the plant species from other plant species, an accurate identification can be made since morphological characters are the sole basis of distinguishing most of the world’s plant species. However, unprocessed botanicals that do not contain all the plant parts necessary to include adequate morphological characters to assure the correct species should have other identity aids or tests to assure the identity of the botanical. [page 12208]⁵

Further, in its discussion of the Proposed Rule on GMPs, FDA clarifies the requirements for laboratory control procedures (Proposed 21CFR Section 111.60(b)(iv)) as follows:

Use of criteria for selecting standard reference materials used in performing tests and examinations. An authenticated plant reference material may be used as standard reference material in performing certain organoleptic examinations [organoleptic refers to having an effect on the sense organs; used in subjective testing of food and drug products]. An authenticated plant reference material is material that has been authenticated as the correct plant species by a qualified plant taxonomist. As described earlier in this document, an organoleptic examination may be an appropriate examination to confirm plant identity when sufficient morphological characters are present to separate the plant species from other plant species. [page 12208]⁵

Here FDA points to the mandatory use of reference materials that are (by definition) well-characterized and authenticated either by compendial reference or in-house measures. With this stance FDA takes the position that reference materials such as vouchers are necessary to conform to requirements for laboratory controls established in the proposed GMPs. As additional evidence of the importance FDA applies to voucher specimens, in the recently-published Guidance for Industry concerning Botanical Drug Products (i.e., not dietary supplements, but FDA-approved drugs made from botanical materials), FDA emphasizes the use of the voucher specimen as a reference for the identity of the botanical material used. FDA states:

A botanical drug substance can be derived from one or more botanical raw materials. The following recommendations apply to each individual botanical raw material used...Identification by trained personnel of the plant, plant parts, alga, or macroscopic fungus used, including organoleptic, macroscopic, and microscopic examination. The identification should be done against a voucher specimen (reference specimen).⁶

Moreover, other countries are coming to the conclusion that the voucher specimen is vital for affirming the identity of botanical materials. For example, in Australia, the Therapeutic Goods Administration (TGA) is implementing the use of voucher specimens as a mandatory reference material.⁷ As the regulations in the U.S. and other countries evolve, the use of voucher specimens becomes increasingly mandatory for regulatory compliance. This demonstrates clear recognition of the validity and meaningful nature of the certified voucher.

Historically, members of the botanical industry have been very trusting in their reliance on representations from suppliers. When asked: “What do I have?” the answer was typically, “My supplier knows for sure.” Buyers too often have relied on the representations made in “certificates of analysis” that were often inaccurate, not documented, or intentionally misleading. The reality is that this trust was often misplaced. With imminent GMP regulations mandating the application of good science over trust, it becomes essential to have a paper trail to the botanical source of every lot of herbal material. A few companies in the industry have for many years included the use of voucher specimens in assuring the identification of the plant materials they incorporate in their products. However, this practice is not as widespread as many industry quality experts, and others, would like. With the prospect of new GMPs forthcoming from FDA, it is likely that this practice may be more widely adopted.

Whether for labeling, certificates of analysis, reducing liability, internal quality assurance (QA), marketing purposes, or in-house training—it is the opinion of these authors that nothing can replace or be substituted for a botanical voucher. Bulk crude botanical materials characterized by TLC and microscopy must refer to a voucher specimen and be retained within the lab facility for reference. Further chemical testing can be useful to provide additional information to complement the botanical identification provided by the voucher.

Without this traceability (i.e., the paper trail to a botanical voucher sample), the information is incomplete and not substantive. If a company’s internal QA is fully implemented, the identity and the reference trail can be traced fully to the source of supply and the proper identity (the Latin name) of the plant. As an alternative to establishing an in-house herbarium containing vouchered specimens, a company can contract with a third-party laboratory to provide this service if the lab has been thorough in its botanical methodology. However, it is the preference of these authors that a company make the relatively small—and reasonable—investment to have these resources in its own possession so that when and if regulatory and legal conflicts arise, it will be able to resolve them immediately.

Example of Incorrect Identification in the Scientific Literature

A famous example of misidentification occurred in a university laboratory in Germany.

When first investigating the properties of some herbal material purportedly in the genus Echinacea at the University of Munich, the plant materials were not correctly identified. Extraction and analysis were conducted and the researchers found what they believed were four novel sesquiterpenes that had previously not been reported in the genus Echinacea. A paper and two poster presentations at professional meetings announcing the discovery were published^8,9,10 and later retracted when it was learned that the plant material was not echinacea, but Parthenium integrifolium,¹¹ a plant in the family Asteraceae and sold in the U.S. herb market as “Missouri Snake Root” (a common name that was also used for E. purpurea). The first modern report of the adulteration problem was published in HerbalGram in 1985.¹² The discovery of the misidentified plant material in the scientific reports—and the subsequent reporting of the misidentification error—occurred after American botanical author Steven Foster sent herbarium specimens of Parthenium to the Munich research group.

The FDA has authorized the use of the American Herbal Products Association’s Herbs of Commerce¹³ for identifying plants on the product label by their more commonly used names.¹⁴ However, even this use of common names hearkens to Linnaeus and the scientific Latin binomial terminology he formalized. The first step in the critical process of applying good science to the manufacture of botanical teas, dietary supplements, and other herbal preparations is knowing not only the proper scientific name(s) of the plant from which any botanical material is derived, but also having adequate authentication and confirmation of the plant’s accurate botanical identification. Linnaeus provided the appropriate scientific language to use for good botanical science. Botanical voucher specimens are useful and mandatory tools in applying good science to the herb manufacturing process. When the publication of the Final Rule on GMPs is published, presumably during the summer of 2004, according to some FDA spokespersons, FDA will mandate the application of this good science to herb manufacturing. Beginning now, the language of Linnaeus becomes the universal language for regulatory compliance.

Trish Flaster is Executive Director of Botanical Liaisons, an ethnobotanical consulting firm providing botanical standards to industry, academicians, and government agencies; international botanical sourcing; sustainable development of botanical ingredients; intellectual property rights; development and implementation of Botanical Quality Assurance programs; and botanical research that results in unique products.

Jim Lassiter has an MS in Biochemistry (Analytical Methods), an MBA, and 25 years experience in regulatory affairs for the pharmaceutical, dietary supplement, and natural products industries, including 14 years with Nutrilite. He is currently Director of Consulting & Regulatory Affairs at Chromadex International.

References:

1. Benson L. Plant Classification. Lexington, Massachusetts: D.C. Heath and Company; 1979.

2. Raven PH, Evert RF, Curtis H. Biology of Plants. New York: Worth Publishers Inc; 1976.

3. Child RE, ed. Conservation and the Herbarium. Institute of Paper Conservation, Leigh; 1994.

4. Bye RA Jr. Voucher specimens in ethnobotanical studies and publications. Journal of Ethnobiology. 1986;6(1):1-8.

5. Current Good Manufacturing Practice in Manufacturing, Packing or Holding Dietary Ingredients and Dietary Supplements: Proposed Rule. Federal Register Vol. 68, No. 49, Docket No. 96N-0417. Washington, DC: Food and Drug Administration. March 13, 2003;12158-12263.

6. U.S. Department of Health and Human Services. Food and Drug Administration Center for Drug Evaluation and Research (CDER). Guidance for Industry Botanical Drug Products. June 2004, Section VIII(B)(1).

7. Australian Government, Department of Health and Aging, Therapeutic Goods Administration, Questions and Answer for the Identification of Herbal Materials and Extracts, Version 1. 25 May 2004.

8. Bauer R, Khan I, Lotter H, and Wagner H. New constituents of Echinacea purpurea. Paper presented at International Research Congress on Natural Products, 7-12 July, 1985, at the University of North Carolina, Chapel Hill.

9. Bauer R, Khan I, Lotter H, Wagner H, Wray V. Structure and stereochemistry of new sesquiterpene esters from Echinacea purpurea (L.) Moench. Helv Chim Acta. 1985, 68:2355-2358.

10. Bauer R, Khan I, Jurcic K, Wagner H, Wray V. Immunologically active sesquiterpene esters from Parthenium integrifolium and adulterant of Echinacea purpurea. Poster presented at Biologically Active Natural Products Symposium Phytochemical Society of Europe, 3-5 Sept. 1986, Lausanne, Switzerland.

11. Bauer R, Khan IA, Wagner H. Echinacea Nachweis einer Verfälschung von Echinacea purpurea (L.) Moench mit Parthenium integrifolium L. (Detection of Parthenium integrifolium L. adulteration of Echinacea purpurea (L.) Moench), Deutsche Apotheker Zeitung. 1987;127(25):1325-1330.

12. Foster S. Herb Traders Beware. HerbalGram. 1985;2(1):3.

13. McGuffin M, Kartesz J, Leung A, Tucker A. Herbs of Commerce. 2nd ed. Silver Spring, MD: American Herbal Products Association; 2000.

14. Title 21 United States Code of Federal Regulations, Section 101.4(h).

Herbal and botanical illustration evolved long ago from hand-painted engravings to black-and-white drawings, and despite continuing advances in photographic methods, line drawings will remain useful for years to come. They remain the most affordably reproduced form of illustration, especially for large reference works.

Though less realistic than photographs, drawings often convey more information. The artist can outline the shape of individual leaves within a mass of foliage, omit irrelevant features such as damaged or diseased leaves, and emphasize inconspicuous characters such as small hairs or glands. Botanical illustration requires as much artistic judgement as photography, and scientific figures can also be works of art.

The figure of scullcap and germander, drawn by Barbara Alongi, is from a forthcoming manual that addresses the identification of common botanicals. Botanical specimens or material in commerce may be dried and broken, shriveled or faded, and may not much resemble the pristine plant in a photograph. Line drawings, which lack distracting color and dimensionality, draw attention to the small anatomical details that are truly important to identification. Line drawings can compliment botanical vouchers but are not replacements.

Wendy L. Applequist, PhD