Authentication of Rhodiola Roots and Root Extracts by HPTLC

Reviewed: Khokhlova K, Zdoryk O. Authentication of Rhodiola rosea, Rhodiola quadrifida and Rhodiola rosea liquid extract from the Ukrainian market using HPTLC chromatographic profiles. Nat Prod Res. 2020; 34(19):2842-2846.

Keywords: Rhodiola crenulata, Rhodiola quadrifida, Rhodiola rosea, HPTLC

The quality and authenticity of dietary supplements made from the root of rhodiola (Rhodiola rosea, syn. Sedum roseum, Crassulaceae) has been the subject of several publications,^1-3 including the BAPP Bulletin on Adulteration of Rhodiola (Rhodiola rosea) Rhizome and Root and Extracts.³ In this investigation, nine high-performance thin-layer chromatography (HPTLC) methods were compared to establish the most suitable conditions as a test assay for the authentication of R. rosea roots in the Ukrainian Pharmacopoeia. The test methods included conditions outlined in the United States Pharmacopeia (USP),⁴ the Russian Pharmacopoeia,⁵ and the Pharmacopoeia of the USSR from 1990,⁶ in addition to several methods developed by the authors. Ultimately, the USP method was proposed to be included as the official method for authentication of rhodiola in the Ukrainian Pharmacopoeia.

Using the HPTLC conditions outlined in the USP, eleven samples of commercial whole, chopped, or powdered R. rosea roots from various geographical origins (Altai: n = 7, Carpathian Mountains: n = 1, not specified: n = 3), ten samples of R. quadrifida roots, and one sample of R. crenulata roots were analyzed. Also evaluated were three commercial products obtained from the Ukrainian market containing liquid extracts of rhodiola.

The rhodiola root samples could be separated into two groups based on the HPTLC fingerprint. Seven samples showed a consistent fingerprint with prominent bands for rosavin, rosarin, and salidroside, while the remaining four samples were devoid of these marker compounds. These four samples generally had a ‘weak” fingerprint (i.e., barely visible bands) but exhibited a similar chemical composition. The authors hypothesized that these four samples may not have been properly processed, and the results could be due to enzymatic degradation. This underscores the importance of obtaining multiple authenticated samples and processing them in the same manner to determine the intraspecific variations and establish relevant baselines for identification.

The HPTLC fingerprints of the commercial liquid extracts all looked similar but were more consistent with profiles for R. crenulata than R. rosea, but the results could also be due to degradation of the main marker compounds, use of low-quality root material, or inefficient extraction techniques.

Comment: The occurrence of two chemically different groups of rhodiola materials raises questions about the variability in the chemical composition of rhodiola roots. The authors indicated that all crude test samples complied with macroscopic and microscopic identification specifications, and also had the characteristic odor of rose that helps to differentiate R. rosea from other Rhodiola species. As such, the four samples that showed an unusual fingerprint appear be authentic but do not comply with pharmacopeial specifications. Additional information on the exact collection site, and data on the root age and on post-harvest processing might have helped to explain some of these differences.

Based on the HPTLC fingerprints of the commercial liquid extracts, it appears that these extracts were made with R. crenulata. This is consistent with other publications that have reported R. crenulata as a common substituent of R. rosea.³ Dietary supplement manufacturers that list Rhodiola rosea on their label must ensure that that their identity tests can unequivocally distinguish among the various Rhodiola species in commerce, and that their product contains solely R. rosea as ingredient.

References

1. Booker A, Jalil B, Frommenwiler D, Reich E, Zhai L, Kulic Z, Heinrich M. The authenticity and quality of Rhodiola rosea products. Phytomedicine. 2016;23(7):754-762.
2. 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.
3. Bejar E, Upton R, Cardellina II JH. Adulteration of Rhodiola (Rhodiola rosea) rhizome and root and extracts. Botanical Adulterants Prevention Bulletin. Austin, TX: ABC-AHP-NCNPR Botanical Adulterants Prevention Program. 2017:1–8.
   
4. Rhodiola rosea. USP 40 - NF 35. Rockville, MD: United States Pharmacopeial Convention; 2017:6805-6807.
5. Russian Pharmacopoeia. XIII ed. Moscow, Russia: Ministry of Health of the Russian Federation; 2016. Available at: http://pharmacopoeia.ru/fs-2-5-0036-15-rodioly-rozovoj-kornevishha-i-korni. Accessed November 12, 2020. [Russian].
6. Arzamastsev AP, Kosyireva NS, editors. Gosudarstvennaya farmakopeya SSSR [State SSSR Pharmacopoeia]. 11th ed. Moscow, Russia: Meditsina; 1990. [Russian].