Investigation into the Authenticity of Commercial Reishi Supplements Sold in the United States

Reviewed: 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. doi:10.1038/s41598-017-06336-3.

Keywords: Adulteration, Ganoderma lucidum, GC-MS, gel electrophoresis, HPSEC-MALLS-RID, HPTLC, polysaccharides, reishi, size exclusion chromatography, triterpenes

The fruiting body of reishi (Ganoderma lucidum, Ganodermataceae) is a popular ingredient in Asian systems of traditional medicine, such as traditional Chinese medicine or Kampo medicine (Japan). It is used to support the immune system, to strengthen the heart, to improve conditions of insomnia, forgetfulness, fatigue, poor appetite and digestive issues, and to alleviate cough.¹ Reishi is also sold as a dietary supplement in Western countries, but investigations into the quality of products labeled to contain reishi are rare, maybe in part due to the challenges in finding appropriate markers for the identity and quality of the species.

In this collaboration among scientists from the University of Macau and the United States Pharmacopeia (USP), a number of chemical methods were developed and used to determine the authenticity of 19 dietary supplements, purchased in the United States from the Internet (Amazon.com and Ebay.com) and labeled to contain powdered fruiting body [6], fruiting body with added polysaccharides [1], various extracts [11], or mycelium [1], by comparing the profiles and color reactions to those of an authentic sample collected in China.

The chemical methods included high-performance thin-layer chromatographic (HPTLC) analysis of the triterpenes, a colorimetric assay for the polysaccharides, compositional analysis of monosaccharides by gas chromatography coupled with mass spectrometry (GC-MS) after hydrolysis of the polysaccharides, saccharide mapping using polyacrylamide gel electrophoresis with UV detection, and the determination of the contents and molecular weight of the polysaccharides by high-performance size exclusion chromatography coupled with multi angle laser light scattering and refractive index detection (HPSEC-MALLS-RID).

A HPTLC triterpene fingerprint similar to authentic reishi was obtained for eight (42.1%) of the 19 samples. The colorimetric assay, a simple assay to detect starch-like polysaccharides using the iodine-potassium iodide reagent, suggested that starch had been added to 13 (68.4%) of the samples. This was confirmed by the results of the gel electrophoresis, the GC-MS data, and the high-performance size exclusion chromatograms. One sample that did not show the presence of starch had a markedly different polysaccharide composition than authentic G. lucidum. Based on the overall results, only five products (26.3%) complied with the ingredient claim stated on the label.

Comment: Several species of Ganoderma can be sold as reishi according to the second edition of the American Herbal Product’s Association’s Herbs of Commerce.² These include G. lucidum, G. japonicum, and G. tsugae. The common name for G. applanatum, which is also present in the US market, is artist’s conk. One difficulty in investigating the authenticity of reishi supplements is that the taxonomy of this genus has been described by botanical authorities as “chaotic”.^3,4 There is a nomenclatural debate as to how Ganoderma should be classified, with some authors recognizing that G. lucidum is not a valid name for ‘reishi’ originating in Asia. Rather it is proposed that G. lucidum is a European species and that materials labeled as G. lucidum from Asia are actually G. lingzhi.⁵ In addition, some reishi products labeled to contain “mushroom” may have been made of mycelium. Mycelia are often grown on grain containing substantial amounts of starch, which could partially explain why starch was found in 13 of the 19 samples.

One aspect of reishi analyses that complicates identification at the species level is that chemically, the fruiting bodies of Ganoderma species are comparatively similar, with polysaccharides, glycoproteins, proteins, and triterpenes as the main constituents.^1,6,7 However, extracts of the fruiting body are readily distinguished from mycelium extracts, e.g., using the HPTLC triterpene fingerprint or analyzing the polysaccharide hydrolysate. While the fruiting body hydrolysate contains various amounts of glucose, galactose, mannose and fucose, the mycelium hydrolysate is almost exclusively composed of glucose.

The fact that only 26.3% of the tested products were found to be authentic suggests an immediate need for improved quality control measures. While the authors acknowledge that the sample size in this study is limited, they indicate that these 19 products “almost represented the G. lucidum dietary supplements available in USA market.”

References

1. Upton R. American Herbal Pharmacopoeia and Therapeutic Compendium: Reishi mushroom: Ganoderma lucidum: Standards of Analysis, Quality Control and Therapeutics. Scotts Valley, CA: American Herbal Pharmacopoeia; 2000.
2. McGuffin M, Leung A, Tucker AO. Herbs of Commerce. 2^nd edition. Silver Spring, MD: American Herbal Products Association; 2000.
3. Zhou L-W, Cao Y, Wu S-H, et al. Global diversity of the Ganoderma lucidum complex (Ganodermataceae, Polyporales) inferred from morphology and multilocus phylogeny. Phytochemistry. 2015;114:7-15
4. Liao B, Chen X, Han J, et al. Identification of commercial Ganoderma (Lingzhi) species by ITS2 sequences. Chin Med. 2015;10:22.
5. Cao Y, Wu S-H, Dai Y-D. Species clarification of the prize medicinal Ganoderma mushroom “Lingzhi.” Fungal Diversity. 2012;56(1):49-62.
6. Ha DT, Loan LT, Hung TM, et al. An improved HPLC-DAD method for quantitative comparisons of triterpenes in Ganoderma lucidum and its five related species originating from Vietnam. Molecules. 2015;20:1059-1077.
7. Ferreira ICFR, Heleno SA, Reis FS, et al. Chemical features of Ganoderma polysaccharides with antioxidant, antitumor and antimicrobial activities. Phytochemistry. 2015;114:38-55.