Thursday, 23 April 2015

What the devil is in your phytomedicine? Exploring species substitution in Harpagophytum through chemometric modeling of 1H-NMR and UHPLC-MS datasets

Phytochemistry
Volume 106, October 2014, Pages 104–115

What the devil is in your phytomedicine? Exploring species substitution in Harpagophytum through chemometric modeling of 1H-NMR and UHPLC-MS datasets


doi:10.1016/j.phytochem.2014.06.012
Get rights and content

Highlights

•
Harpagophytum procumbens and H. zeyheri are currently used interchangeably.
•
UHPLC-MS analysis shows that harpagoside content is higher in H. procumbens (0.17–4.37%) than in H. zeyheri (0.00–3.07%).
•
PCA and OPLS-DA analysis revealed cluster formation based on species.
•
Biomarkers (retention time-mass/charge ratio pairs) were identified using OPLS-DA.
•
Harpagophytum procumbens and H. zeyheri are not chemically equivalent.

Abstract

Harpagophytum procumbens (Pedaliaceae) and its close taxonomical ally Harpagophytum zeyheri, indigenous to southern Africa, are being harvested for exportation to Europe where phytomedicines are developed to treat inflammation-related disorders. The phytochemical variation within and between natural populations of H. procumbens (n = 241) and H. zeyheri (n = 107) was explored using proton nuclear magnetic resonance (1H-NMR) and ultra-high performance liquid chromatography coupled to mass spectrometry (UHPLC-MS) in combination with multivariate data analysis methods. The UHPLC-MS results revealed significant variation in the harpagoside content: H. procumbens (0.17–4.37%); H. zeyheri (0.00–3.07%). Only 41% of the H. procumbens samples and 17% of the H. zeyheri samples met the pharmacopoeial specification of ⩾1.2%. Both principal component analysis (PCA) and orthogonal projections to latent structures discriminant analysis (OPLS-DA) indicated separation based on species (UHPLC-MS data OPLS-DA model statistics: R2X = 0.258, R2Y (cum) = 0.957 and Q2(cum) = 0.934; 1H-NMR data OPLS-DA model statistics: R2X = 0.830, R2Y = 0.865 (cum) and Q2(cum) = 0.829). It was concluded that two species are not chemically equivalent and should not be used interchangeably.

Graphical abstract

The results showed that Harpagophytum procumbens and H. zeyheri are not chemically equivalent and therefore should not be used interchangeably as a source of Devil’s Claw as proposed in the pharmacopoeias.
Full-size image (29 K)

Keywords

  • Harpagophytum procumbens;
  • Harpagophytum zeyheri;
  • Pedaliaceae;
  • Devil’s Claw;
  • Chemometrics;
  • Nuclear magnetic resonance;
  • Ultra-high performance liquid chromatography-mass spectrometry;
  • Iridoid glycosides;
  • Harpagoside

Corresponding author at: Department of Pharmaceutical Sciences, Tshwane University of Technology, Private Bag X680, Pretoria 0001, South Africa. Tel.: +27 12 382 6373; fax: +27 12 382 6243.
Copyright © 2014 Elsevier Ltd. All rights reserved.
at