Extracts of the secondary roots of the southern African plant Harpagophytum procumbens (Devil's Claw) provide an herbal drug with a variety of traditional indications. It is a member of the sesame family (Pedaliaceae), and the genus Harpagophytum contains the species (Fig. 6.1) H. zeyheri, extracts of which were also mixed with Hp extracts in earlier studies. Monographs state Hp as the sole source of the medicinal drug.
The natives of the Kalahari and Savannah desert regions of southeast and southern Africa used the dried secondary roots of the plant to treat a variety of ailments including fever, malaria and indigestion. Since its introduction into Europe during
the middle of the last century, the anti-inflammatory properties of extracts of Devil's Claw  have attracted the most attention. The European Scientific Cooperative on Phytotherapy (ESCOP) issued a monograph recommending its use in the symptomatic treatment of painful osteoarthritis, relieving lower back pain, loss of appetite and dyspepsia , and the EMEA Committee on Herbal Medicinal Products (HMPC) have recently issued a draft monograph for discussion in which an indication for treatment of mild articular pain and mild digestive disorders is proposed on the basis of traditional use . Its use in the treatment of inflammatory disorders of the musculoskeletal system and of lower back pain has become particularly popular in recent years. The clinical evidence of Devil's Claw use in treating painful osteoarthritis is generally good and has been the topic of several recent reviews. However, more studies are required in order to establish this drug as a definitive therapeutic option. Issues such as the optimal dose and duration of treatment need to be resolved .
This chapter will review the published evidence that Hp extracts exert anti-inflammatory effects that are of relevance to the therapeutic use of Hp extracts in os-teoarthritis. Although osteoarthritis is generally considered a degenerative disease, recent new insight into the pathophysiology of osteoarthritis reveals that inflammatory processes are involved in the early stages of the disease and are not only secondary processes following tissue degeneration. The breakdown of cartilage is probably the initial problem in osteoarthritis, but there is good evidence from human studies that this process involves the release of proinflammatory cytokines such as TNF and IL1 from chondrocytes within the cartilage .
There is good in vitro and in vivo pharmacological evidence of the anti-inflammatory and analgesic properties of Hp, although some negative findings have also been reported . Generally, the pharmacological profile of Hp extracts is supportive of its therapeutic potential as an anti-inflammatory agent. More evidence is, however, needed in more clinically relevant models. Also, more information on the mode of action of extracts of Hp and of its constituents, and especially the identification of the cellular and molecular targets, is required before the full potential of this highly promising therapeutic plant can be appreciated. Its anti-inflammatory properties certainly warrant further research.
Treatment of painful inflammatory diseases has received a major blow with the "fall from grace" of the cyclooxygenase (COX)2 inhibitor drugs due to problems of cardiovascular risk. Thus, there is a desperate need for new anti-inflammatory drugs. The therapeutic potential of novel anti-inflammatory drugs appears to extend beyond chronic inflammatory diseases such as osteoarthritis, rheumatoid arthritis and chronic inflammatory bowel disease. Inflammatory processes are seen today as playing a significant pathophysiological role in many common modern diseases such as cardiovascular disease, diabetes, osteoporosis, neurode-generative diseases, dementia and Alzheimer's disease, as well as in carcinogenesis.
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