The drug-extract-ratio of aqueous/ethanolic Harpagophyti radix extracts has to be revised

The ratio of the herbal substance to the herbal preparation (drug-extract ratio=DER) is one of the most important criteria to approve the therapeutic equivalence of different herbal preparations. The approval itself is very important in simplified registration procedures. The herbal guideline of SWISSMEDIC [1] is an example thereof: DER is placed on second position of totally nine criteria. Dingermann [2] called for a DER-declaration in its natural range. Actually, there is a discrepancy between the published DER and the DER in its natural range of ethanolic Devil's Claw [Harpagophytum progumbens (Burch.) DC ex Meissn.] root extracts. A DER of 4.4–5:1 is declared for most of the products in Germany. This is not the DER of the native extract in its natural range. A study with ethanol/water mixtures of 0 to 95% of ethanol showed a low DER for all mixtures up to 70%. The results are reproducible. DER has therefore to be reduced to 1.5–2.5:1 as it is correctly done for water extracts. A native ethanolic (60%) extract has been analytically compared with a commercially available extract of a declared DER 4.4–5:1. No phytochemical differences could be detected: Iridoid glycosides, saccharides, phenylethyl-derivatives [3, 4] and plant acids have been analysed by HPLC quantitatively; TLC-fingerprint has been adapted additionally to the lipophilic fraction. A percolation of the cutted, dried root showed no differences in the chemical composition of the three main fractions. In all the extracts and fractions, a high amount of stachyose (ca 45%) has been detected. We conclude that the declared DER of most of the ethanolic Devil's Claw products is not in accordance with the natural range. A special extraction procedure can be excluded due to phytochemical equivalence. A revision is necessary. As a consequence, the ESCOP [5] (and other) recommendations for the dosage of Devil's Claw roots have to be corrected from 2–5g of the drug per day down to 1.5–3g/day for painful osteoarthritis or to 1000mg/day for extracts.

References: 1. Swissmedic (2004), Anleitung zum Einreichen von Zulassungsgutachten für pflanzliche Arzneimittel der Humanmedizin (Phyto-Anleitung), Paragraph IV A1). 2. Dingermann, T. (2000), Transparenzkriterien für pflanzliche, homöopathische und anthroposophische Arzneimittel. Karger-Verlag, Freiburg und Basel. ISBN 3–8055–7045–7. 3. Boje, K. et al. (2003), Planta Med. 69: 820–825. 4. Munkombwe, N.M. (2003), Phytochem. 62: 1231–1234. 5. The Scientific Foundation for Herbal Medicinal Products (2003), ESCOP-Monographs, Second Edition, Harpagophyti radix, Thieme, Stuttgart, New York, pp. 233–240.