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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, collect safety and tolerance
information and compare the antioxidant, and anti-inflammatory
actions of in vitro. 

Materials and methods: Forty-five patients with osteoarthritis
of the knee were recruited, 30 were treated with freezedried, and 15 with placebo. Hematological
parameters were assessed on entry and exit of the four-week
trial. Pain, medical and subject assessment scores and
adverse effects were collected at weeks 1, 2 and 4. The
antioxidant and anti-inflammatory activity of the cat’s claw
species was determined by the a,a-diphenyl-b-picrylhydrazyl
(DPPH) free radical scavenging method. Inhibition of
TNFa and prostaglandin E2 (PGE2) production was determined
in RAW 264.7 cells by ELISA. 

Results: Cat’s claw had no deleterious effects on blood or liver
function or other significant side-effects compared to
placebo. Pain associated with activity, medical and patient
assessment scores were all significantly reduced, 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.
indicated that
were equivalent
at quenching DPPH radicals (EC50 , 13.6–21.7 mg/ml) as
well as inhibiting TNFa production. However, the latter
action was registered at much lower concentrations (EC50,
10.2–10.9 ng/ml). Cat’s claw (10 mg/ml) had no effect on
basal PGE2 production, but reduced LPS-induced PGE2
release (P < 0.05), but at higher concentrations than that
required for TNFa inhibition. 

Conclusion: Cat’s claw is an effective treatment for
osteoarthritis. The species,
are equiactive. They are effective antioxidants, but their antiinflammatory
properties may result from their ability to
inhibit TNFa and to a lesser extent PGE2 production.