Harpagophytum

Harpagophytum (/ˌhɑːrpəˈɡɒfɪtəm/ HAR-pə-GOF-it-əm), also called grapple plant, wood spider, and most commonly devil's claw, is a genus of plants in the sesame family, native to southern Africa. Plants of the genus owe their common name "devil's claw" to the peculiar appearance of their hooked fruit. Several species of North American plants in the genus Proboscidea and certain species of Pisonia, however, are also known by this name. Devil's claw's tuberous roots are used in folk medicine to reduce pain.[1]

Devil's claw
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Lamiales
Family: Pedaliaceae
Genus: Harpagophytum
DC. ex Meisn.
Species
Dry fruit of H. procumbens - MHNT
Plate from "Icones selectae plantarum", vol. 5: t. 94 (1846)
San man collecting devil's claw in Namibia (2017)

Range

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

Folk medicine and research

The ethnobotanical use of devil's claw originated in southern Africa.[2] H. procumbens is one of the floral emblems of Botswana where it is thought to be useful in treating a variety of pain conditions.[3]

Preparations of the plant or its extracts, such as harpagoside,[4] are presumed to have uses in folk medicine and phytotherapy as an anti-inflammatory herbal drug or dietary supplement.[1] Although there is no accepted clinical evidence of its efficacy and bioavailability, limited effects were noted for treating lower back pain and osteoarthritis.[1]

A Cochrane review of clinical research noted that devil's claw seems to reduce low back pain more than placebo, although evidence was of moderate quality at best.[5]

Adverse reactions

Side effects and drug interactions with nonsteroidal anti-inflammatory drugs may occur, and caution exists for a variety of conditions, such as pregnancy and cardiovascular disorders.[1] Devil's claw may cause diarrhea and may interfere with the action of ticlopidine and warfarin.[1]

Ecology and management

Harpagophytum procumbens inhabits deep, sandy soils, and occurs in areas with low annual rainfall (150–300 mm/year). It is a perennial, tuberous plant with annually produced creeping stems. The above-ground stems emerge after the first rains and die back during droughts or after frosts. The stems grow from a persistent primary tuber and several secondary tubers (the harvested organs) grow from the primary tuber at the end of fleshy roots. The plant gets its scientific and common names from the hooked spines of its woody capsules (see photo). The mature fruit opens slowly so that, in a given year, only 20-25% of its seeds may establish soil contact. Seeds have a high degree of dormancy. They have a low respiration rate and may remain viable in the seed bank for more than 20 years.

The sustainability of the trade in devil’s claw has been questioned for several years. The governments of the each of the countries in which it occurs (range states; Namibia, Botswana, and South Africa) have developed policies and regulations to protect the species, to determine a sustainable harvest, and to provide for continued livelihoods for the harvesters. At various times, the species has been proposed for protection by the Convention of International Trade in Endangered Species (CITES). However, the range states have implemented measures to manage the trade sustainably and the proposal to protect the species by CITES was withdrawn.[6]

Various studies have examined the biological and ecological requirements of harvested and unharvested populations. Several early short-term studies in Botswana examined the ecological requirements of the species.[7][8][9][10][11][12] Other, somewhat more recent studies inventoried the resource and examined sustainable harvesting methods.[13][14][15]

The ecological requirements of a harvested species must be known to manage the harvest of the species to ensure it is sustainable. Stewart and Cole (2005)[6] examined the complex economic, social, and cultural factors involved in the harvest of the species. Stewart (2009)[16] examined population structure, density, growth, mortality, and seed and fruit production in harvested and unharvested populations in the Kalahari savannas of South Africa. Plant density and population structure differed significantly between overgrazed and grass-dominated areas, suggesting that the differences may be due to competition for scarce water and nutrients. Experimental removal of secondary tubers (harvest) was not a significant factor for mortality in any of the harvested size classes. Harvest also did not affect growth, although plants in the medium size class grew more during the study period in both the harvested and unharvested populations. Fruit production was highly variable, and mature fruits were produced only under favorable conditions. Under the conditions of this experimental harvest, the species appears to be resilient to harvest, with plants subjected to harvest surviving as well as unharvested plants. However, due to the spatially variable nature of its habitat and the plasticity of the plants themselves, harvesting data from actual harvested areas from a large number of plants is required to better understand the life history of the species.

References
  1. "Devil's claw". MedlinePlus, US National Library of Medicine, National Institute of Medicine. 2015. Retrieved 29 April 2015.
  2. Mncwangi, N.; Chen, W.; Vermaak, I.; Viljoen, A.M.; Gericke, N. (2012). "Devil's Claw - a review of the ethnobotany, phytochemistry and biological activity of Harpagophytum procumbens". J Ethnopharmacol. 143 (3): 755–71. doi:10.1016/j.jep.2012.08.013. PMID 22940241.
  3. Pelontle, Kedirebofe (13 May 2014). "Department unveils national symbols". DailyNews. Botswana Press Agency (BOPA). Retrieved 12 July 2016.
  4. "Harpagoside". PubChem, US National Library of Medicine. 2016. Retrieved 13 July 2016.
  5. Gagnier, J. J.; Oltean, H.; Van Tulder, M. W.; Berman, B. M.; Bombardier, C; Robbins, C. B. (2016). "Herbal Medicine for Low Back Pain: A Cochrane Review". Spine. 41 (2): 116–33. doi:10.1097/BRS.0000000000001310. PMID 26630428.
  6. Stewart, K.M.; Cole, D. (2005). "The commercial harvest of devil's claw (Harpagophytum spp.) in southern Africa: the devil's in the details". Journal of Ethnopharmacology. 100: 225–236. doi:10.1016/j.jep.2005.07.004.
  7. LeLoup S. (1984). An ecophysiological approach of the influence of harvest on the population dynamics of the grapple plant Harpagophytum procumbens DC. The Grapple Plant Project: Second Progress Report. Report prepared for the National Institute for Development and Research and Documentation of Botswana.
  8. Veenendaal, E.M. (1984). Regeneration and productivity of the grapple plant Harpagophytum procumbens DC under harvesting pressure. The Grapple Plant Project: First progress report. Report prepared for the National Institute for Development and Research and Documentation of Botswana.
  9. Burghouts, T. (1985). Water balances and productivity of the grapple plant Harpagophytum procumbens DC. The Grapple Plant Project: Fourth Progress Report. The Grapple Plant Project: First progress report. Report prepared for the National Institute for Development and Research and Documentation of Botswana.
  10. De Jong, F.E. (1985). Further aspects of regeneration and productivity of the grapple plant Harpagophytum procumbens DC under harvesting pressure. The Grapple Plant Project: Third Progress Report. Report prepared for the National Institute for Development and Research and Documentation of Botswana.
  11. Kok, E. (1986). Regrowth and tuber quality of juvenile grapple plants, Harpagophytum procumbens DC and their transpiration. The Grapple Plant Project: Third Progress Report. Report prepared for the National Institute for Development and Research and Documentation of Botswana.
  12. Hulzebos, E. (1987). Fruit development and tuber production of a desert perennial, Harpagophytum procumbens. The Grapple Plant Project: Sixth Progress Report. Report prepared for the National Institute for Development and Research and Documentation of Botswana.
  13. Hachfeld, B.; Schippmann, U. (2002). Occurrence and density of Harpagophytum procumbens in Namibia and South Africa. Proceedings of the Regional Devil’s Claw Conference 26–28 February 2002. Windhoek, Namibia (Ed CRIAASA-DC).
  14. Hachfeld, B. (2003). Ecology and utilization of Harpagophytum procumbens (devil’s claw) in southern Africa. Federal Agency for Nature Conservation, Bonn. Plant Species Conservation Monograph No. 2.
  15. Strobach, M., Cole, D. & Schippmann, U. (2007). Population dynamics and sustainable harvesting of the medicinal plant Harpagophytum procumbens in Namibia. Unpublished report prepared for the Federal Agency for Nature Conservation, Bonn Germany.CS1 maint: multiple names: authors list (link)
  16. Stewart, K.M. (2009). "Effects of secondary-tuber harvest on populations of devil's claw (Harpagophytum procumbens) in the Kalahari savannas of South Africa". Journal of African Ecology. 48: 146–154. doi:10.1111/j.1365-2028.2009.01093.x.

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