Efficacy and safety of freeze-dried cat's claw in osteoarthritis of the knee: mechanisms of action of the species Uncaria guianensis

Aim: The purpose of this investigation was to evaluate the ability of cat's claw, an Amazonian medicinal plant, to treat osteoarthritis of the knee, c ollect safety and tolerance information and compare the antioxidant, and an ti-inflammatory actions of Uncaria guianensis and Uncaria tomentosa in vitr o. Materials and methods: Forty-five patients with osteoarthritis of the knee were recruited, 30 were treated with freeze-dried U. guianensis, and 15 wit h placebo. Hematological parameters were assessed on entry and exit of the four-week trial. Pain, medical and subject assessment scores and adverse ef fects were collected at weeks 1, 2 and 4. The antioxidant and anti-inflamma tory activity of the cat's claw species was determined by the alpha,alpha - diphenyl-beta -picrylhydrazyl (DPPH) free radical scavenging method. Inhibi tion of TNF alpha and prostaglandin E-2 (PGE(2)) production was determined in RAW 264.7 cells by ELISA. Results: Cat's claw had no deleterious effects on blood or liver function o r other significant side-effects compared to placebo. Pain associated with activity, medical and patient assessment scores were all significantly redu ced, with benefits occurring within the first week of therapy. Knee pain at rest or at night, and knee circumference were not significantly reduced by cat's claw during this brief trial. In vitro tests indicated that U. guian ensis and U tomentosa were equivalent at quenching DPPH radicals (EC50, 13. 6-21.7 mug/ml) as well as inhibiting TNF alpha production. However, the lat ter action was registered at much lower concentrations (EC50, 10.2-10.9 ng/ ml). Cat's claw (10 mug/ml) had no effect on basal PGE(2) production, but r educed LPS-induced PGE(2) release (P < 0.05), but at higher concentrations than that required for TNF alpha inhibition. Conclusion: Cat's claw is an effective treatment for osteoarthritis. The sp ecies, U. guianensis and U. tomentosa are equiactive. They are effective an tioxidants, but their antiinflammatory properties may result from their abi lity to inhibit TNF alpha and to a lesser extent PGE(2) production.