FWD 2 Botanical Adulterants Monitor: Commercial Reishi Supplements Sold in the United States Identified as Ganoderma lingzhi by DNA Barcoding
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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.

References

  1. Loyd AL, Barnes CW, Held BW, Schink MJ, Smith ME, Smith JA, Blanchette RA. Elucidating "lucidum": Distinguishing the diverse laccate Ganoderma species of the United States. PLoS One. 2018;13(7): e0199738.
  2. Zhou LW, Cao Y, Wu SH, Vlasák J, Li DW, Li MJ, Dai JC. Global diversity of the Ganoderma lucidum complex (Ganodermataceae, Polyporales) inferred from morphology and multilocus phylogeny. Phytochemistry. 2015;114:7–15.
  3. Wang XC, Xi RJ, Li Y, Wang DM, Yao YJ. The species identity of the widely cultivated Ganoderma, ‘G. lucidum’ (Ling–zhi), in China. PLoS One. 2012;7:e40857.
  4. Richter C, Wittstein K, Kirk MP, Stadler M. An assessment of the taxonomy and chemotaxonomy of Ganoderma. Fungal Diversity. 2015;71(1):1–15.
  5. Dai YC, Zhou LW, Hattori T, Cao Y, Stalpers JA, Ryvarden L, Buchanan P, Oberwinkler F, Hallenberg N, Liu PG, Wu SH. Ganoderma lingzhi (Polyporales, Basidiomycota): the scientific binomial for the widely cultivated medicinal fungus lingzhi. Mycol Prog. 2017;16(11-12):1051-55.
  6. McGuffin M, Kartesz JT, Leung AY, Tucker AO. American Herbal Products Association’s Herbs of Commerce. 2nd ed. Silver Spring, MD: American Herbal Products Association; 2000.
  7. Loyd AL, Richter BS, Jusino MA, Truong C, Smith ME, Blanchette RA, Smith JA. Identifying the "mushroom of immortality": assessing the Ganoderma species composition in commercial reishi products. Front Microbiol. 2018;9:1557.
  8. Wu D-T, Deng Y, Chen L-X, Zhao J, Bzhelyansky A, Li S-P. Evaluation on quality consistency of Ganoderma lucidum dietary supplements collected in the United States. Sci Rep. 2017;7:7792.
  9. Moley T, Foster S, Awang D, Hu SY, Kartesz JT, Tucker AO. Herbs of Commerce. 1st ed. Austin, TX: American Herbal Products Association; 1992