Investigation into the Quality of Rhodiola spp. Raw Materials Using ¹H NMR and HPTLC

 

Reviewed: Booker A, Zhai L, Gkouva C, Li S, Heinrich M. From traditional resource to global commodities:–A comparison of Rhodiola species using NMR spectroscopy–metabolomics and HPTLC. Front Pharmacol. 2016;7:254. doi: 10.3389/fphar.2016.00254.

 

Keywords: Rhodiola rosea, Rhodiola crenulata, Rhodiola spp., adulteration, substitution, ¹H NMR, HPTLC

 

The roots of Rhodiola rosea (syn. Sedum rosea,* S. roseum, Crassulaceae) are frequently used in herbal medicine as an adaptogen, and are indicated for temporary relief of symptoms of stress, such as fatigue and sensation of weakness.¹ However, overharvesting and habitat destruction have led to lower availability, an increase in pricing, and an increased risk of adulteration. In this study, the phytochemical profiles among samples of Rhodiola spp. sold as a crude drug, decoction pieces, or in the form of a teabag cut were evaluated by proton nuclear magnetic resonance (¹H NMR) spectroscopy and high-performance thin-layer chromatography (HPTLC). The results were compared to profiles of authentic R. rosea, R. crenulata, R. fastigiata, R. quadrifida, and R. sachalinensis root and rhizome using multivariate statistics (¹H NMR) or visual analysis (HPTLC).

 

According to the supplemental information, 46 samples were obtained from various institutes (n=5), the Internet (n=5), markets (n=14), and retailers (n=22). Of these samples, three were considered standard materials, but were also submitted to analytical testing. Results of one rhodiola tea sample from Russia were not included in the paper. The origin of the materials was predominantly China, with only one sample from Russia and one sample from Germany. The samples were labeled to contain R. rosea (n=11), R. crenulata (n=7), R. quadrifida (n=3), R. sachalinensis (n=4), or an unspecified Rhodiola species (n=20). Overall, 30% of the market samples did not contain the species declared on the label. Over half of the samples with an undisclosed Rhodiola species contained R. crenulata (n=11), while the remainder consisted of R. serrata (n=2), R. gelida (n=1), or could not be attributed (n=6). The paper does not detail what criteria were used to identify samples as R. gelida and R. serrata (listed only in the supplemental information), but one of the authors explained in a personal communication that species determination was performed by DNA analysis (A. Booker email communication, December 1, 2016).

 

Both the ¹H NMR method and the HPTLC method allowed the distinction of the Rhodiola species with the exception of R. rosea and R. sachalinensis, the differentiation of which proved to be challenging. Rhodiola sachalinensis has a similar array of secondary metabolites, including rosavin, which has been proposed as a marker compound to authenticate R. rosea, and some botanical databases even list the two species as synonyms for the same plant.^2,3 Rhodiola crenulata, on the other hand, is readily distinguished from R. rosea: admixture of 20% R. crenulata to R. rosea could be detected with both ¹H NMR and HPTLC methods. The ability to detect lower amounts of adulterants was not investigated by the authors.

 

Comment: The appropriately chosen title of the paper, “from traditional resource to global commodities,” provides an insight into the rationale behind some of the quality issues that are observed in the herbal supply chain. Increased demand, combined with a limited growing range and slow reproduction of R. rosea, has put pressure on the supply chain. The fact that R. rosea is listed in the European Medicines Agency’s (EMA) community herbal monograph,¹ but R. crenulata is the official species in the Chinese Pharmacopoeia,⁴ causes important problems in the trade (M. Heinrich email communication, December 1, 2016). In addition, the interchangeable use of Rhodiola species in local traditional medicine systems, the similar Chinese Pinyin names, and the introduction of more abundant and thus lower-cost Rhodiola species have led to a situation where the authenticity and quality of crude R. rosea root material is highly variable. The results of this investigation confirm data from a previous investigation into the authenticity of rhodiola material sold as decoction pieces in the Chinese market,⁵ and at the same time the authors have provided appropriate analytical methods to evaluate the identity and quality of R. rosea raw materials.

 

*According to relevant botanical texts,^6-9 the accepted scientific name of rhodiola is Sedum rosea (S. roseum). However, the American Herbal Products Association’s Herbs of Commerce, 2nd ed.,¹⁰ lists Rhodiola rosea as the scientific name, and this is the name that is used in the herbal community, and by the dietary supplement industry for labeling commercial products.

 

References

1.     European Medicines Agency Committee on Herbal Medicinal Products (HMPC). Community herbal monograph on Rhodiola rosea L., rhizoma et radix. London, UK: European Medicines Agency; 2012. Available at: http://www.ema.europa.eu/docs/en_GB/document_library/Herbal_-_Community_herbal_monograph/2012/05/WC500127863.pdf. Accessed December 13, 2016.

2.     Sedum roseum (L.) Scop. The Plant List. Version 1.1 (September 2013). Available at: http://www.theplantlist.org/tpl1.1/record/kew-2475525. Accessed December 13, 2016.

3.     Sedum roseum (L.) Scop., Fl. Carniol., ed. 2, 1: 326 (1771). Medicinal Plant Names Services Portal. Surrey, UK: Royal Botanic Gardens, Kew. Available at: http://mpns.kew.org/mpns-portal/plantDetail?plantId=475525&query=sedum+roseum&filter=&fuzzy=false&nameType=all&dbs=wcsCmp. Accessed December 13, 2016.

4.     Chinese Pharmacopoeia Commission. Rhodiola crenulata. Pharmacopoeia of the People’s Republic of China. Vol 1. English ed. Beijing, China: China Medical Science and Technology Press; 2010:376-377.

5.     Xin T, Li X, Yao H, et al. Survey of commercial Rhodiola products revealed species diversity and potential safety issues. Sci Rep. 2015;5:8337. doi: 10.1038/srep08337.

6.     The Plant List. Version 1.1 (September 2013). Available at: http://www.theplantlist.org/. Accessed December 13, 2016.

7.     Tropicos.org. Missouri Botanical Garden. Available at: http://www.tropicos.org/. Accessed December 13, 2016.

8.     Mabberley DJ. Mabberley’s Plant-Book: A Portable Dictionary of Plants, their Classification and Uses. 3rd ed. Cambridge, UK: Cambridge University Press; 2008.

9.     Fernald ML. Sedum rosea, not S. roseum. Rhodora. 1947;49(579):79-81.

10.  McGuffin M, Kartesz JT, Leung AY, Tucker AO. Herbs of Commerce. 2nd ed. Silver Spring, MD: American Herbal Products Association; 2000.