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Devil's claw

harpago-collecte600
Harpagophytum procumbens
Pedaliaceae
Devil's claw
Grapple plant, Wood spider
Root

Devil’s claw has been used in traditional African medicine to treat a variety of disorders including cough, diarrhea, constipation, syphylis and gonoorrhea.The Namibian Herero also used a tea of the dried roots of Devil's claw  for the treatment of pain. Devil's claw preparations were used agaist lumbago and of wounds at the Okawango. Another African traditional use of locally applied Devil's claw preparations is to ease pain in childbirth. The treatment was continued after giving birth with an orally applied powder of dried roots [1]. 

The discovery of Harpagophytum procumbens is generally ascribed to the German settler Hubertus Mehnert [1], who most likely found out about the medicinal virtues when he was in an internation camp during World War II (see also the entry on Gottreich Hubertus Mehnert under "Who is who" in www.namibiana.de).  Since these first studies the roots of Devil's claw have become an important part of European phytotherapy, especially for the treatment of osteoarthritis, rheumatic pain and back pain.

The first reference on the use of aqueous Harpagophytum extract for arthritis dates back to 1958. Since then, powdered crude plant material, aqueous and ethanolic extracts from the roots have been part of European traditional medicines for osteoarthritic and low back pain [2, 3]. Officialy authorised uses in medicinal products are, e.g., the 

Supportive treatment of mild back, neck und muscle pain, morning stiffness and mild pain in tendons and joints, as in rheumatic disorders of knee, hip or shoulders.

 

References

[1] Anon. (1996). Harpagophytum procumbens (Burchell) DC. ex Meisner subsp. procumbens. In: Eberhard v. Koenen: Heil- Gift- und essbare Pflanze in Namibia. Klaus Hess Verlag, Göttingen 1996, Edition Namibia, Vol. 2, p.126

[2] Vlachojannis J, Roufogalis BD, Chrubasik S. (2008). Systematic review on the safety of Harpagophytum preparations for osteoarthritic and low back pain. Phytotherapy Research 22(2):149-152.

[3] EMA: Final Community Herbal Monograph on Harpagphytum procumbens DC and/or Harpagophytum zeyheri DECNA, radix. EMEA, HMPC 251323/2006

Harpago-CultureWeedy, perennial herb with creeping stems that spread from a thick primary root that is surrounded by tuberous secondary roots. It bears greyish-green leaves, tubular yellow and violet flowers and large, hooked, claw-like fruit.

The common name is derived from the unusual appearance of the fruits, which appear to be covered in small hooks. The appearence of the fruits is reflected in the scientific name: "Harpago" refers to "grapple", "phytum" to "plant" - grapple plant. "procumbens" means prostrate, and refers to the ground-hugging, creeping growth form of the aerial plant parts. 

 

Habitat

Harpagophytum procumbens DC. ex Meisn., most commonly referred to as devil's claw (also grapple plant, or wood spider), is from the Pedaliaceae or sesame family, and native to Southern Africa. 

Harpagophytum is a bitypic genus, with both species being native to Southern Africa. The two species are Harpagophytum procumbens and H. zeyheri: however, distinguishing between the species can be problematic due to the variety of morphotypes. Reliable identification of species is generally by the fruit [1]. Both species grow in the Kalahari sands (albeit their habitats do hardly overlap), but the fruits of H. zeyheri have much shorter spiny arms than those of H. procumbens.

Harpagophytum procumbens is mainly found in the eastern and southeastern parts of Namibia, Southern Botswana and the Kalahari region of the Northern Cape, South Africa. Harpagophytum zeyheri, is found in the northern parts of Namibia (North of the Etosha plain) and southern Angola.  

Devil's claw grows mostly in sandy soils. It usually occupies plains, dune bases and interdunes. Soils are usually sandy or rocky and most often nutrient poor. The plants are geophytes, being dormant in winter and can therefore probably withstand some frost.

Botany

Harpagophytum procumbens  is a prostrate, sprawling plant with a stout, perennial rootstock with a group of secondary storage tubers arising from it. It is a perennial herb with a succulent taproot. The annual, creeping stems can be up to 2 m long. They grow from a primary (or “mother”) tuber whose taproot can be up to 2 m deep. Secondary tubers (called “babies”) develop on root strings growing from the primary tuber. The secondary roots are usually around 25 cm long and 6 cm thick. The secondary tubers contain stachyose, a photosynthetic storage product, thought to be an adaptation to drought conditions. Trailing annual stems bear opposite leaves. These are irregularly 3-5-lobed and appear grey- green due to a covering of tiny white mucilage cells which may help cut down water loss.

The flowers are trumpet-shaped, tubular, 5-6 cm long, and range in colour from pale pink to red. The tube base and mouth are yellowish; they can be all yellow, all purple or white. The very distinctive spiny fruits, from which many of the common names are derived, are woody, oval and flattened capsules armed with two central spines and two lateral rows of twelve to sixteen horny arms bearing hooked spine. The many seeds are roughly oblong and dark brown or black. The plants flower mainly from about November to April (summer) and have fruits from about January.

Conservation Status

Devil’s claw is assessed as Least Concern (LC) according to IUCN Red Data List criteria in South Africa and Namibia, it is however assessed as Near Threatened in Botswana. Devil’s claw is classified as a protected species in Botswana, Namibia and South Africa. Permits are required for harvesting and exporting it. Both species of Harpagophytum are listed under CITES in Annex D. No part of the tubers or roots can be traded within the European Union without proper licenses.

The main threat to devil's claw is over-harvesting for medicinal use. The tubers are an important source of income for many people living in the Kalahari. Wild harvesting of devil’s claw tubers can be sustainable if only some of the tubers are taken and if enough are left behind for the plants to regenerate. However, in some regions the tubers have been over-collected and the species is becoming rarer. Most of the world's supply of Devil’s claw comes from Namibia, with lesser quantities from South Africa and Botswana. Since Devil's claw has been exported to Germany and first been clinically examined in 1958, the international demand has risen substantially. Namibia has exported 1018 tons of dried tubers in 2002, involving the harvest of millions of plants [2].

A major impediment to sustainable harvesting is the low price paid to harvesters. The Sustainably Harvested Devil's Claw (SHDC) project in Namibia (which began in 1997) suggests that improved benefit sharing for harvesters leads to better resource management and conservation by giving harvesters a financial incentive to ensure the tubers are not over-harvested. The project also shows the importance of traditional knowledge (e.g. the best time to harvest, and how to avoid damaging the plants). The project contributed to the development of Namibia's policy on devil's claw and scientific research on the impact of harvest on growth rates to determine annual sustainable yields.

So far the theory. Devil's claw could easily be grown in cultivation or at least obtained by controlled collection, but with the exception of few cultivation projects the effort has not been made so far for economic reasons. After the rarification of the plant in Namibia due to overharvesting the reaction of the EU regulators was not to encourage cultivation, but rather to include the related species H. zeyheri as a replacement species. Although H. zeyheri has an inferior quality, frequently not meeting the standards defined by the European Pharmacopeia, the blending of roots of Harpagophytum procumens easily meeting the standard with roots of inferior H. zeyheri allows reaching the defined limits at mimimum costs. Harpagophytum zeyheri is collected in Angola, where the workers are paid even much less than in Namibia. Blending is therefore economically interesting.

However, in both cases the roots are from uncontrolled wild crafting with no measures taken to procect sustainability. It is only a matter of time until for H. zeyheri as well there will be a rarification of this species as well, or until the availability of Harpagophytum procumens becomes so scarce that the minimum contents of harpagoside defined by the European Pharmacopeia can no longer be guaranteed. When this point is reached the cultivation may again become an economically viable option. The corresponding cultivation techniques have already been developed and allow growing Harpagophytum without the use of herbicides or pesticides, and a minimum of water for irrigation, delivering roots with extraordinaryly high contents of active constituents.

References

[1] Muzila M, Setshogo MP, Mpoloka SW (2011). Multivariate analysis of Harpagophytum DC. ex Meisn (Pedaliaceae) based on fruit characters. International Journal of Biodiversity and Conservation. 3(3):101-109.

[2] Stewart KM, Cole D (2005). The commercial harvest of devil's claw (Harpagophytum ssp.) in southern Africa: the devil's in the details. Journal of Ethnopharmacology 100(3): 225-236.

Devil’s claw contains 0.5 to 3% iridoid glucosides primarily the bitter tasting harpagoside, and the slightly sweetly tasting harpagide, as well as 8-(4-coumaroyl)-harpagide, procumbide, its 6’-4’-coumaroyl ester and procumboside.

Devil’s claw also contains sugars including stachyose, raffinose and monosacchararides; as well as flavonol glycosides including verbascoside (= acteoside) and isoacteoside; triterpenes, mainly oleanic acid, phytosterols, mainly b-sitosterol, stigmasterol and their glycosides. 

The European Pharmacopoeia specified a content of 1.2 % harpagoside in the dried roots. Harpagoside as a so-called iridoid compound has been associated with antimicrobial and anti-inflammatory effects, which explains the use of Devil’s claw preparations against degenerative-rheumatic complaints such as arthrosis.

In screening studies in Namibia a range of 1.7 to 3.8 % total iridoids, and 1.1 to 2.8 % harpagoside were found in samples of authenticated Harpagophytum procumbens. In contrast, the replacement species Harpagophytum zeyheri showed distinctly lower contents with 0.8 to max. 1.7 % harpagoside, but very similar total iridoid contents [1]. H. zeyheri contains a second major iridoid: 8-p-coumaroyl-harpagide. This latter constituent provides a tool for the assessment of the presence of Harpagophytum zeyheri in root material of Devil’s claw [1,2].

Another constituent potentially contributing to the anti-inflammatory efficacy is acteoside [3], also known as verbascoside. In the screening studies acteoside contents ranged from 1.5 to 2.5 %. Acteoside has been shown effective in models of inflammation [4], and would therefore deserve more attention in future studies on Devil’s claw.

References

[1] Eich J, Schmidt M, Betti G (1998). HPLC-Analysis of iridoid compounds of Harpagophytum taxa: Quality control of pharmaceutical drug material. Pharmaceutical and Pharmacological Letters 8(4): 75-78.

[2] Baghdikian B, Lanhers MC, Fleurentin J, Ollivier E, Maillard C, Balansard G, Mortier F (1997). An Analytical Study, Anti-Inflammatory and Analgesic Effects of Harpagophytum procumbens and Harpagophytum zeyheri. Planta Medica 63: 171-176.

[3] Burger J, Brandt E, Vincent E, Ferreira D (1987). Iridoid and phenolic glucosides from Harpagophytum procumbens. Phytochemistry 26(5): 1453-1457.

[4] He J, Hu XP, Zeng Y, Li Y, Wu HQ, Qiu RZ, Ma WJ, Li T, Li CY, He ZD (2011). Advanced research on acteoside for chemistry and bioactivities. Journal of Asian Natural Products Research 13(5): 449-464.

harpago-contrle-biomasse 600Medicinal usage is from the thick lateral tubers, which are cut into slices and dried.

The root is collected at the end of the rainy season. The traditional use of devil’s claw by African tribes involved chopping and drying the root in the sun for three days to make medicinal preparations. Devil’s claw has been used in traditional African medicine to treat a variety of disorders including cough, diarrhea, constipation, syphylis and gonoorrhea. Another African traditional use of locally applied Devil's claw preparations is to ease pain in childbirth. The treatment was continued after giving birth with an orally applied powder of dried roots. The Namibian Herero also used a tea of the dried roots of Devil's claw  for the treatment of pain. Devil's claw preparations were also used agaist lumbago and of wounds at the Okawango [1].  Harpagophytum procumbens and H. zeyheri, both known locally as Ekakataf in the Ohshikoto region of Namibia, is traditionally used long term for epilepsy [2].

The discovery of Harpagophytum procumbens is generally ascribed to the German settler Hubertus Mehnert [1], who most likely found out about the medicinal virtues when he was in an internation camp during World War II (see also the entry on Gottreich Hubertus Mehnert in the section "Who is sho" of www.namibiana.de). The running story about Mehnert having discovered the plant by followong an African healer with the aid of a hunting dog after the healer was unwilling to reveal the source of his miracle cure is obviously just a myth, traceable to a very successful marketing story of the first pharmaceutical companies selling Harpagophytum in Germany [3]. More serious sources refer to first scientific studies by Zorn (1958), who received the plant material for his studies on the treatment of rheumatic complaints by Mehnert himself [4]. Traces of Mehnerts life can still be found in Namibia, among others his tomb on his farm in the region of Maltahöhe.

Modern day use of devil's claw is frequently by standardised tablets that retain the bitter substances. Devil’s claw is also available as a tincture, liquid extract and tea. The European Pharmacopoia requests that the plant material for the manufacture of the galenical formulations must contain no less than 1.2 percent of harpagoside.

References

[1] Anon. (1996). Harpagophytum procumbens (Burchell) DC. ex Meisner subsp. procumbens. In: Eberhard v. Koenen: Heil- Gift- und essbare Pflanze in Namibia. Klaus Hess Verlag, Göttingen, Edition Namibia, Vol. 2, p.126

[2] Cheikhyoussef A, Shapi M, Matengu K, Ashekele HM (2011). Ethnobotanical study of indigenous knowledge on medicinal plant use by traditional healers in Oshikoto region, Namibia. Journal of ethnobiology and ethnomedicine. 7:10.

[3] Anon. (1973). Die Teufelskralle aus der Kalahari-Wüste Südwestafrikas jetzt auch in Europa. Afrikaner heilen Rheuma mit Harpago! Heim und Welt, Issue 42.

[4] Zorn B (1958). Über die antiarthritische Wirkung der Harpagophytum-Wurzel. (Vorläufige Mitteilung). Z. f. Rheumaforschung 17: 134-138.

Uses

  • Folks medicine: Cardiovascular diseases, musculoskeletal disorders including arthritis, gout and rheumatoid arthritis, digestive disorders including anorexia, digestive weakness and diarrhoea, anxiety, migraine, neuralgia.
  • Britisch Herbal Pharmacopoeia (BHP): Rheumatism, arthritis, gout, myalgia, fibrositis, lumbago, pleurodynia. Specific indication: rheumatic disease
  • World Health Organisation (WHO): Treatment of pain associated with rheumatic conditions. Treatment of loss of appetite and dyspeptic complaints; supportive treatment of degenerative rheumatism, painful arthrosis and tendonitis
  • European Scientific Cooperative on Phythotherapy (ESCOP): Symptomatic treatment of painful osteoarthritis, relief of lower back pain, loss of appetite and dyspepsia
  • German Commission E: Loss of appetite, dyspepsia, degenerative disorders of the locomotive system

The foundation for European marketing authorisations is the monograph of the European Medicines Agency's Herbal Medicinal Product Committtee:

  • European Medicines Agency (EMA) / Herbal Medicinal Procucts Committee (HMPC): Traditional herbal medicinal product for relief of minor articular pain / Traditional herbal medicinal product used for the relief of mild digestive disorders such as bloating and flatulence and where there is loss of appetite [1].

In typical products on the EU market, this may translate into

Supportive treatment of mild back, neck und muscle pain, morning stiffness and mild pain in tendons and joints, as in rheumatic disorders of knee, hip or shoulders.

References

[1] EMA: Final Community Herbal Monograph on Harpagphytum procumbens DC and/or Harpagophytum zeyheri DECNA, radix. EMEA, HMPC 251323/2006

 

The monograph of the European Medicines Agency (EMA) defines the doses traditionally used for the relief of minor articular pain  and minor digestive disorders such as bloating and flatulence and where there is loss of appetite [1]. Specifically for the use against rheumatic complaints the EMA monographs gives dosing recommendations for different forms, among others: 

  • Tea: 4.5 g in 500 ml of water, divided in thee single doses
  • Root powder: 1.35 g/day, divided in three doses
  • Dry extract with water, drug-extract ratio = 1.5-2.5:1 (i.e., 1 g of extract corresponds to 2 g of dry root material): 300 mg to 2.4 g daily, divided in 2-3 doses.

A typical medicinal product containing devil's claw extract would, for example, contain 600 mg of dry extract (1,5-2.5:1, extraction solvent water), to be taken at a dose of 3-4 tablets daily, e.g., two tablets in the morning and two in the evening.

Patients should be advised that it might take three to four months for maximum pain relief to occur and not give up too soon [2]. 

References

[1] EMA: Final Community Herbal Monograph on Harpagphytum procumbens DC and/or Harpagophytum zeyheri DECNA, radix. EMEA, HMPC 251323/2006

[2] Thanner J, Kohlmann T, Kunzel O, Chrubasik S (2009). Retrospective evaluation of biopsychosocial determinants and treatment response in patients receiving devil's claw extract (doloteffin). Phytotherapy research 23(5): 742-744.

 

The European Medicines Agency's monograph on Harpagophytum procumbens calls for the following potential adverse events to be mentioned in product informations of herbal medicinal products containing devil's claw roots:

  • Gastrointestinal disorders (diarrhea, nasea, vomiting, abdominal pain
  • Headache, dizziness
  • Allergic skin reactions

The frequency of these potential adverse reactions is not known [1]. 

Caution is recommended for patients suffering from gastric or duodenal ulcers, or patients with cardiovascular disorders [1].

Devil’s claw has a very low toxicity [2,3] 1,2. A safety review of devil’s claw preparations for osteoarthritic and low back pain published in 2008 analysed 28 studies published over a period of nearly 30 years (from 1980 to 2007, involving a total of 6892 patients). In none of the double-blind studies was the incidence of adverse events during treatment with devil’s claw higher than during placebo treatment. Minor adverse events occurred in around 3 % of the patients, mainly gastrointestinal adverse events. A few reports of acute toxicity were found but there were no reports on chronic toxicity [4].

The contra-indication for patients with cardiovascular disorders is not derived from clinical observations, but from a model of an isolated rabbit heart treated with a crude devil's claw extract prepared with methanol as an extraction solvent [5,6] - such an extract does not exist as an active constituent in medicinal products. In this model, perfusion of the isolated rabbit heart with compareatively high quantities of the extract resulted in a protection against arrhythmia. The authors hypothesised that devl's claw might have a verapamil-like effect on intracellular calcium currents, and that therefore it should be  used with caution in patients affected by cardiovascular disorders. Apparently this clinically non-confirmed hypothesis was sufficient to include a warning label in the product information of devil's claw preparations as a precautionary measure.

Drug interactions

Little is known about possible herb-drug interactions arising from effects of Devil's Claw on the major drug metabolizing enzymes or transporters.  A recent study evaluated the effects of devil’s claw on the multidrug transporter ABCB1/P-glycoprotein in vitro. Devil’s claw extracts were able to inhibit P-glycoprotein activity, even if to a different extent, while pure harpagoside was almost ineffective [7].  The clinical significance of this finding is unknown. There are no published case reports of drug interactions. 

Experience shows that in vitro studies on pharmacokinetic interactions are not of great worth to predict interactions in humans. Interactions on the level of PGP, a transporter system involved in the excretion and thus detoxification of drugs, would normally be observed as a lack of efficacy of concomitantly taken drugs metaboised through the same system, which is the majority of drugs. Correspondingly, such an effect would most likely be known from clinical observations in cases of drugs where the concomitant intake of other drugs is rather the rule than the exception, as it is the case with rheumatic disorders. The monograph of the European Medicines Agency conclusively states that interactions with other drugs are not known [1].

References

[1] EMA: Final Community Herbal Monograph on Harpagphytum procumbens DC and/or Harpagophytum zeyheri DECNA, radix. EMEA, HMPC 251323/2006

[2] Erdös A, Fontaine R, Friehe H, Durand R, Poppinghaus T (1978). Beitrag zur Pharmakologie und Toxikologie verschiedener Extrakte, sowie des Harpagosids aus Harpagophytum procumbens DC. Planta Medica 34(1):97-108.

[3] ESCOP (2009): Harpagophyti Radix. Devil's Claw Root. In: ESCOP Monographs - The Scientific Foundation for Herbal Medicinal products. Thieme, Stuttgart, Ed. 2, p. 135-146.

[4] Vlachojannis J, Roufogalis BD, Chrubasik S (2008). Systematic review on the safety of Harpagophytum preparations for osteoarthritic and low back pain. Phytotherapy Research 22(2): 149-152.

[5] Circosta C, Occhiuto F, Ragusa S, Trovato A, Tumino G, Briguglio F, De Pasquale A (1984). A drug used in traditional medicine: Harpagophytum procumbens DC. II. Cardiovascular activity. Journal of Ethnopharmacology 11(3): 259-274.

[6] Costa De Pasquale R, Busa G, Circosta C, Iauk L, Ragusa S, Ficarra P, Occhiuto F (1985). A drug used in traditional medicine: Harpagophytum procumbens DC. III. Effects on hyperkinetic ventricular arrhythmias by reperfusion. Journal of Ethnopharmacology 13(2):193-199.

[7] Romiti N, Tramonti G, Corti A, Chieli E (2009). Effects of Devil's Claw (Harpagophytum procumbens) on the multidrug transporter ABCB1/P-glycoprotein. Phytomedicine 16(12): 1095-1100.

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Preparations of the roots of the South African medicinal plant "Devil’s claw“ (Harpagophytum procumbens) are traditionally used for the treatment of rheumatic complaints, mainly of the degenerative type (arthrosis). Typical applications are back pain and osteoarthritis [1].

The practical applicability of Devil’s claw in medical practise has been described in studies, many of them open trials or case reports, but also reference- or placebo-controlled double-blind trials. The effect against osteoarthritis was found as good as with the reference diacerein [2,3]. The use of this comparator medicine is justified by a meta- analysis of clinical studies confirming an advantage of diacerein over placebo [4], thus retrospectively validating the conclusion of mild effects of Devil’s claw against osteoarthritis.

 Similarly, Devil’s claw had been found efficacious against back pain, e.g., in a clinical double-blind study with rofecoxib as a comparator [5]. Again, the efficacy of rofecoxib (and therefore also of Devil’s claw) has been demonstrated in clinical double-blind trials in the treatment of back pain [6,7]. The muscle pain-relief through Devil’s claw has also been shown in a placebo-controlled trial [8], as was the efficacy against rheumatic disorders of the hip joint [9].

Warnock et al. (2007) consider Devil’s claw as an effective and well-tolerated serious treatment option for mild to moderate degenerative rheumatic disorders [10]. The analgesic efficacy has also been accepted in a Cochrane review [11].

Summarising, Devil’s claw clearly is efficacious at least in mild to moderate cases of rheumatic complaints. Even as an on-top therapy on-top therapeutic option it may contribute to improving the quality of life of patients suffering from degenerative and painful symptoms of rheumatism.

References

[1] Vlachojannis J, Roufogalis BD, Chrubasik S. (2008). Systematic review on the safety of Harpagophytum preparations for osteoarthritic and low back pain. Phytotherapy Research 22(2):149-152.

[2] Chantre et al. (2000)

[3] Leblan et al. (2000)

[4] Bartels et al. (2010)

[5] Chrubasik et al. (2003)

[6] Fine (2002)

[7] Katz et al. (2004)

[8| Goebel et al. (2001)

[9] Frerick et al. (2001)

[10] Warnock et al. (2007)

[11] Gagnier et al. (2007)