Issue: 63 Page: 32-37
Quality Control in Herbal Preparations: Using Botanical Reference Standards for Proper Identification
by Trish Flaster, Jim Lassiter
HerbalGram. 2004; 63:32-37 American Botanical Council
Quality Control in Herbal Preparations: Using Botanical Reference Standards
for Proper Identification
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,
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
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
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
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
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 published8,9,10 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.
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
Wendy L. Applequist, PhD