The South African „Devil’s claw“ carries the scientific botanical name Harpagophytum procumbens De Candolle. The roots of this plant are traditionally used against joint disorders. This use is supported by a monograph of the Herbal Medicinal Product Committee(HMPC) of the European Medicines Agency. The quality of Devil’s claw roots is specified by a monograph of the European Pharmacopoeia (Ph. Eur.), which calls for a minimum content of 1.2 % of harpagoside as a quality marker.
Both, the HMPC and the Ph.Eur.-monograph, also allow the use of a second species of the same gender: Harpagophytum zeyheri Decaisne. The possibility for using this replacement species seems, however, more dictated by economic realities than by a real exchangeability between species. There is little evidence proving that both species are in fact equally valuable for medicinal use. When offered the choice between both roots – which are virtually undistinguishable, especially when dried and cut – the native Ovahimba from North-West Namibia will always give preference to H. procumbens, and reject H. zeyeri (personal observation of G. Betti). There are also distinct differences with respect to the content of harpagoside: H. zeyheri shows much lower contents than H. procumbens, to an extent that it is difficult to reach the minimum of 1.2 % without blending materials from the two species.
According to our observations, there are no significant observations of transition forms or hybrids on site. The habitats of Harpagophytum procumbensare found well South of Etosha National Park in Namibia, all the way down South to the Republic of South Africa. In our field work we found increasing harpagoside contents from North to South and from West to East, decreasing again towards the extreme South of Namibia/North of the Republic of South Africa. The characteristics are obviously genetically defined: Plant material taken from a site (Inselberg) with roots containing high quantities of harpagoside would not change their rate of harpagoside formation when re-planted in other zones by vegetative multiplication.
The findings of our field project in Namibia and adjacent countries allowed us to establish the method for a sustainable cultivation of high qualityHarpagophytum procumbens in Namibia (Schmidt M et al., 1998).
Schmidt M, Eich J, Kreimeyer J & Betti G. 1998. Anbau der Teufelskralle. Ein Projekt in Namibia zur Sicherung der pharmazeutischen Qualität. Dtsch. Apotheker Ztg. 138, 4540-4549.