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Identification of Major and Minor Constituents of Harpagophytum procumbens (Devil's Claw) Using HPLC-SPE-NMR and HPLC-ESIMS/APCIMS

Cailean Clarkson,^† Dan Strk,^† Steen Honoré Hansen,^‡ Peter J. Smith,^§ and Jerzy W. Jaroszewski*^†

Department of Medicinal Chemistry and Department of Pharmaceutics and Analytical Chemistry, The Danish University of Pharmaceutical Sciences, Universitetsparken 2, DK-2100 Copenhagen, Denmark, and Division of Pharmacology, Department of Medicine, University of Cape Town, K-45 OMB, Groote Schuur Hospital, Observatory 7925, Cape Town, South Africa

J. Nat. Prod., 2006, 69 (9), pp 1280–1288

DOI: 10.1021/np0601612

Publication Date (Web): August 15, 2006

†

Department of Medicinal Chemistry, The Danish University of Pharmaceutical Sciences.

‡

Department of Pharmaceutics and Analytical Chemistry, The Danish University of Pharmaceutical Sciences.

Department of Medicine, University of Cape Town.

Corresponding author. Tel: (45) 35306372. Fax: (45) 35306040. E-mail: jj@dfuni.dk.

Abstract

The HPLC-SPE-NMR technique, supported by HPLC-MS measurements, was used to determine structures of major as well as some minor constituents of ethanol and petroleum ether extracts of Harpagophytum procumbens (Devil's claw) roots. This method was also shown to be applicable for rapid and precise on-line identification of secondary metabolites present in commercial herbal products of H. procumbens. A total of 15 compounds (1−14 and 17) were identified from the ethanol and petroleum ether extracts, including a novel Diels−Alder dimer 14. Optimization of the HPLC-SPE-NMR experiments included quantitative ¹H NMR measurements, determination of trapping and elution efficiency, effect of multiple trapping of analytes, use of various deuterated solvents for SPE cartridge elution, and effect of post-column dilution ratio of eluent with water. Linear accumulation of apolar and relatively polar analytes was demonstrated for at least 8−10 repeated trappings, resulting in greatly improved signal-to-noise ratios in NMR spectra and reduced acquisition times. Thus, the HPLC-SPE-NMR technique provides an efficient means of identification of multiple components of crude extracts. By allowing on-line generation of high-quality 2D NMR data without traditional purification of extract components, the HPLC-SPE-NMR methodology represents a paradigm shift in natural products research with respect to structure elucidation.

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