A HPTLC Fingerprinting Method for
the Authentication of Angelica gigas
and Other Important Apiaceae Members
Reviewed: Frommenwiler DA, Kim J, Yook C-S, Tran TTT, Cañigueral
S, Reich E. Comprehensive HPTLC fingerprinting for quality control of an herbal
drug – the case of Angelica gigas
root. Planta Med. 2018;84(6-7):465-474. doi: 10.1055/a-0575-4425.
Keywords: Adulteration, Angelica
archangelica, Angelica gigas,
Angelica sinensis, Angelica
spp., HPTLC, Levisticum officinale, Ligusticum porteri, Ligusticum spp.
The Forum for the Harmonization of Herbal Medicines (FHH)
is an initiative by the World Health Organization’s (WHO) Western Pacific
regional office with the goals to promote public health by recognizing and
developing standards and technical guidelines that aim to improve the quality,
safety, and efficacy of herbal medicines. One of the deliverables of the FHH is
to make herbal reference materials available that can be used to establish the
identity and quality of herbal ingredients for global use. The FHH selected the
root of Angelica gigas (Apiaceae) to be the
first ingredient for which such reference material should be developed.
In this collaborative effort,
scientists from Korea, Spain, Switzerland, and Vietnam evaluated the natural
variability of A. gigas roots by comparing the
high-performance thin-layer chromatographic fingerprints of 34 samples of A. gigas roots grown in Gangwon province (Republic of Korea)
authenticated by taxonomic, genetic, and microscopic means. In addition, the
HPTLC fingerprint was compared with fingerprints of 26 related species from the
Apiaceae family, including members of the genus Angelica
(n = 10), Levisticum (n = 1), Ligusticum
(n = 9), Notopterygium (n = 2), and Peucedanum (n = 4) to determine if the method was suitable
for authentication of A. gigas. The
fingerprints of all the cultivated A. gigas root
samples were consistent, and distinct enough from other members of the family
Apiaceae to allow an HPTLC-based distinction. Admixture of as little as 5% of A. acutiloba or A. sinensis can
be detected by the presence of the (Z)-ligustilide
band (absent in A. gigas).
The third part of the
project was the establishment of suitable marker compounds for quantitative
analysis. Based on the relatively high concentration, and acceptable resolution
from neighboring compounds, the co-eluting coumarins decursin and decursin
angelate were selected. The concentration of decursin/decursin angelate was
calculated by measuring the fluorescence of the compounds, and comparing it to
the fluorescence values of a decursin calibration curve. A collaborative study
analyzing the same three A. gigas
samples in Korea, Switzerland, and Vietnam showed good agreement among the
quantitative results, which included a number of additional compounds, e.g., (Z)-ligustilide (as a marker of adulteration), imperatorin,
and osthole.
Comment: There are a number of reasons why this paper can be used
as a template for herbal medicine products quality method development. The idea
of harmonizing test methods for herbal ingredients around the globe is not new,
but it is a good example of a collaboration among different countries from two
continents that has led to useful results. Too often, the adoption of uniform
methods in pharmacopeias around the world is hampered by the desire of
individual institutions to have a unique product that can be offered for sale to
the interested stakeholders.
In addition, the large number
of authentic A. gigas root samples from
different producers, and the comparison of 26 additional Apiaceae species of
medicinal interest suggests that this a robust and widely applicable test
method, suitable for identification of these species, and for the detection of
adulteration.
Finally, the inclusion of
orthogonal test methods, such as macroscopic, microscopic, chemical, and
genetic testing, provides an approach that will hopefully be followed by other research
groups with interest in herbal ingredient identification.
There is one caveat of which
those who have analyzed herbal ingredients containing (Z)-ligustilide
are likely aware: the compound is known to degrade readily, and the purity of
commercial standards is often lower than expected.1 As such, the
quantification of (Z)-ligustilide
may not be as straightforward as indicated in this paper.
References
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A, Pro SM, Main M, Chen S-N, Jaki BU, Lankin DC, Pauli GF. The dynamic nature
of the ligustilide complex. J Nat Prod.
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