Commercial
Reishi Supplements Sold in the United States Identified as Ganoderma lingzhi by DNA Barcoding
Reviewed: Gunnels T, Creswell M, McFerrin
J, Whittall JB. The ITS region provides a reliable DNA barcode for identifying
reishi/lingzhi (Ganoderma) from herbal supplements. PLoS One. 2020 15(11): e0236774.
Keywords: Ganoderma lingzhi,
Ganoderma lucidum, lingzhi, reishi,
DNA barcoding
Dietary
supplements containing ingredients derived from the fruiting body or mycelium
of medicinal fungi have been increasingly popular in the United States. Reishi (Ganoderma lucidum/G. lingzhi, Ganodermataceae) supplements are no exception, and have been among
those ingredients with the largest increase in sales in the United States in
the first six months of 2020 (compared to the same time period in 2019) due to
the immunomodulatory effects ascribed of reishi that were in high demand during
the initial months of the COVID-19 pandemic.
As indicated in the Botanical Adulterants Monitor #20, the taxonomy of reishi is a matter of debate. Predominantly
based on DNA evidence, a number of authors suggest that the species G. lucidum, considered by many to consist
of an aggregate of many species, should be separated into G. lucidum sensu stricto and G. lingzhi.1,2 However,
morphological distinction between the species is difficult due to the high
variability within the same species. Therefore, some taxonomists consider macromorphological features
to be of limited value in the identification of Ganoderma species. Adding to the confusion are papers reporting that the widely cultivated
reishi mushroom from China should be called G.
sichuanense,3 since this name precedes the scientific
name “G. lingzhi,”4
while other authors claim that G.
sichuanense is morphologically distinct from G. lingzhi and should be a separate taxon.5
For this investigation,
seven reishi dietary supplement products were bought in natural product retail
stores in the United States. Products were labeled to contain reishi mycelium
(n = 4), mycelium and fruiting body (n = 2), or were made from non-specified
reishi mushroom parts (n = 1). One sample each of Fomitopsis pinicola and Ganoderma
brownii, collected in the wild, were used as controls. After
extraction of the DNA, Ganoderma-specific
primers were used to amplify the ITS region of each sample, and the Sanger
method was used for determining the nucleotide sequence.
The sequence
data were compared to those available in GenBank. All store-bought samples
aligned within a cluster of G. lucidum/G. lingzhi sequences, which the authors
referred to as the G. lingzhi clade (suggesting many G. lucidum
sequences to be misidentified G.
lingzhi), which led the authors
to comment that “Rampant
misidentification of true reishi is highlighted in the authoritative American Herbal Products Association’s Herbs of Commerce, 2nd ed.6
which indicates that the most important species commercially sold under the
common name “reishi” are “G. japonicum, G. lucidum,
and G. tsugae” — completely neglecting what is now considered true
reishi, “G. lingzhi”.
Comment: The substantial growth in the medicinal fungi category
combined with often unclear taxonomic separation and a lack of characteristic
chemical markers put many fungal ingredients at risk for being adulterated. In
this paper, all the commercial reishi supplements contained Ganoderma DNA, contrary to some of the
previously published papers investigating commercial reishi materials.7,8
While herbal dietary
supplement manufacturers should strive to have the correct scientific name for
their ingredients on the label, there are many instances, such as reishi, where
the taxonomy is still a matter of debate, which makes it challenging to apply
the correct Latin binomial. Traditionally, a variety of species of Ganoderma were used as the medicinal
article ling zhi, though
differently colored ling zhi were
recognized. With traditional taxonomy using classical botany as the foundation,
quite often, new names are proposed that are later rejected by the scientific
community. In more recent decades, DNA investigations have been used to propose
numerous taxonomic changes that may or may not be accepted by international
authorities, yet occur in the scientific literature. The taxonomic
recommendations based on genetic information may differ depending on how
similarities and differences are defined. In virtually every case, neither the traditional
use nor a clinical evaluation of the material is considered when making these
taxonomic determinations.
It is easy to understand how a
dietary supplement company may choose a taxonomically established name rather
than use whatever the latest botanical publication may propose. Additionally,
as noted by the authors, the current edition of Herbs of Commerce6 (HOC), is outdated, and the only edition formally
recognized by in the Code of Federal Regulations was released in 1992.9
A large number of nomenclatural changes have been formalized or proposed in the
28 years since this reference was initially published and in the 20 years since
its revision. HOC is currently under revision and may help to clarify some of
these nomenclatural challenges, but as long as pure taxonomic considerations
are divorced from traditional precedent or practical use, nomenclatural confusion
will continue to exist.
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AL, Barnes CW, Held BW, Schink MJ, Smith ME, Smith JA, Blanchette RA.
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T, Foster S, Awang D, Hu SY, Kartesz JT, Tucker AO. Herbs of Commerce. 1st ed. Austin, TX: American Herbal Products Association; 1992