Comparison of different Rhodiola species using NMR- metabolomics and HPTLC techniques

 

The fast developing international trade of products based on local and traditional knowledge and their associated value chains have become an important aspect of the ethnopharmacological debate. The structure and diversity of value chains and their impact on the phytochemical composition of herbal medicinal products (HMPs) has been overlooked in quality issues in transnational trade. Medicinal Rhodiola species, including R. rosea L. and R. crenulata (Hook.f. & Thomson) H.Ohba, abbreviate genus have been widely used as traditional herbal medicines with numerous claims for their therapeutic effects [1]. Faced with resource depletion and environment destruction, R. rosea and R. crenulata are becoming endangered, making them more economically valuable to collectors and middlemen, and also increasing the risk of adulteration and low quality. This study compares the phytochemical differences among Rhodiola raw materials available on the market and provides a practical method for Rhodiola authentication. Nuclear magnetic resonance (NMR) spectroscopy coupled with multivariate analysis software and high performance thin layer chromatography (HPTLC) techniques were used to analyse the phytochemical differences between five Rhodiola species. We compared the phytochemical composition of collected Rhodiola samples to authenticated samples. Rosavin and rosarin were mainly present in R. rosea whereas an unknown compound was only present in R. crenulata. 30% of the Rhodiola samples purchased from the Chinese market were adulterated by other Rhodiola spp. 7% of the raw-material samples were not labelled properly and the species information was not clearly illustrated. Both ¹H-NMR and HPTLC methods provided an integrated analysis of the phytochemical differences between the species studied. This study provided an identification method for R. rosea and R. crenulata and provided further analytical data that could form the basis for the identification of other species. The integrated identification approach combining these two analytical platforms offers an innovative and practical way of assessing the chemical variability along the value chains of medicinal plants.

Acknowledgements: Anthony Booker's research position is funded through a charitable donation by Dr. Willmar Schwabe GmbH & Co. KG, Germany.

Keywords: Rhodiola, quality, adulteration, metabolomics, NMR, HPTLC.

References:

[1] Shikov AN, Pozharitskaya ON, Makarov VG, Wagner H, Verpoorte R, Heinrich M. Medicinal plants of the Russian pharmacopoeia; their history and applications. J Ethnopharmacol 2014; 154: 481 – 536