Admixture and Substitution of Eleutherococcus senticosus and Rhodiola rosea Dietary Supplements with Materials from the Genus Eleutherococcus and Rhodiola, Respectively

Reviewed: Ruhsam M, Hollingsworth PM. Authentication of Eleutherococcus and Rhodiola herbal supplement products in the United Kingdom. J Pharm Biomed Anal. 2018;149:403-409.

Keywords: Adulteration, DNA barcoding, Eleutherococcus senticosus, Eleutherococcus sessiliflorus, Rhodiola rosea, Rhodiola spp.

Using DNA barcoding, these researchers from the Royal Botanical Garden in Edinburgh, Scotland, analyzed 25 eleuthero (Eleutherococcus senticosus, Araliaceae) and 13 rhodiola (Rhodiola rosea, Crassulaceae) dietary supplements purchased in the United Kingdom at herbalist shops or from the internet.

The eleuthero samples consisted of cut root (9), powdered root (7), extracts (8), or a mixture of powdered root and extract (1). The matK region was chosen as the barcode since previously published work had shown that this region can distinguish E. senticosus from other Eleutherococcus species.¹ Each sample was extracted multiple times, and those for which more than one matK sequence was obtained (i.e., those that contained a mixture of species) were submitted to DNA barcoding using the internal transcribed spacer 2 (ITS2) sequence. The ITS2 sequences were compared to those deposited in the GenBank library using the BLAST search tool in order to determine the identity of the added material.

All of the 25 eleuthero materials contained the matK sequence of E. senticosus. However, nine samples provided additional sequences, which matched E. sessiliflorus, E. divaricatus, and E. seoulensis. The authors point to E. sessiliflorus as the most likely adulterant, since its geographic distribution overlaps with eleuthero, and it is also known as “Siberian ginseng” by the local people. (In the United States the common name “Siberian ginseng” is still used for eleuthero, even if the name ‘ginseng’ is now restricted to members of the genus Panax, and shipments labeled as “Siberian ginseng” are considered to be misbranded by the US Food and Drug Administration [FDA]).

The rhodiola dietary supplements were made from powdered root/rhizome (6) cut root (3), extracts (2), or a mixture of an extract with powdered root and rhizome (2). The identity of rhodiola materials was assessed using the ITS2 genetic region by comparison to sequence data published by Zhang et al.² Out of the 10 products that provided DNA of sufficient quality to establish the identity, only five (50%) products were made solely with R. rosea. In two products, the substitute material was identified as R. himalensis, while in two other products, the exact species could not be determined. One sample consisted of a mixture of R. rosea with an unknown Rhodiola species. No Rhodiola DNA was found in the remaining three samples; these products may have contained too highly fragmented rhodiola DNA, and as such were unsuitable for the identity assessment by DNA barcoding.

Comment: This paper raises legitimate concerns about the composition of eleuthero and rhodiola dietary supplements. In Europe and North America, products labeled to contain eleuthero are expected to contain E. senticosus. However, the Chinese common name wu jia pi is used for several Eleutherococcus species, including E. senticosus, E. nodiflorus (syn. E. gracilistylus), E. henryi, and E. sessiliflorus.³ Similarly, the Chinese pin yin name hong jing tian is used for several Rhodiola species which are considered as acceptable substitutes for one another.⁴ Therefore, manufacturers that specify a particular species (i.e., E. senticosus or R. rosea) on their product label should be aware of the interchangeable use of these species in Chinese trade, and implement adequate quality control measurements, e.g., by genetic and/or by chemical means, to ensure that the purchased materials comply with the identity specifications for the desired species.

References

1.     Zhu S, Bai Y, Oya M, Tanaka K, Komatsu K, Maruyama T, Goda Y, Kawasaki T, Fujita M, Shibata T. Genetic and chemical diversity of Eleutherococcus senticosus and molecular identification of Siberian ginseng by PCR-RFLP analysis based on chloroplast trnK intron sequence. Food Chem. 2011;129:1844–1850.

2.     Zhang JQ, Meng SY, Wen J, Rao GY. DNA barcoding of Rhodiola (Crassulaceae): a case study on a group of recently diversified medicinal plants from the Qinghai-Tibetan Plateau. PLoS One. 2015;10(3):e0119921.

3.     Bensky D, Gamble A, Kaptchuk TJ. Chinese Herbal Medicine: Materia Medica. Seattle, WA: Eastland Press.1986.

4.     Bejar E, Upton R, Cardellina II JH. Adulteration of rhodiola (Rhodiola rosea) rhizome and root and extracts. Austin, TX: ABC-AHP-NPNCR Botanical Adulterants Program; 2017. Botanical Adulterants Bulletin.