Antinociceptive and antiedematogenic properties and acute toxicity of Tabebuia avellanedae Lor. ex Griseb. inner bark aqueous extract

BACKGROUND: Tabebuia avellanedae is a tree from the Bignoniaceae family. Commonly know as "pau d'arco" in Brazil, its inner bark is used as analgesic, anti-inflammatory, antineoplasic and diuretic at the Brazilian northeast. A validation of the plant usage has not been previously performed. RESULTS: Antinociceptive and antiedematogenic effects of Tabebuia avellanedae Lor. ex Griseb. inner bark were measured by nociceptive experimental models in mice. A rat paw edema test induced by carrageenan (1%) was also performed in rats to access the plant's antiedematogenic effect. The inner bark aqueous extract, administered via oral in three different concentration, namely 100, 200 and 400 mg/Kg, reduced the nociception produced by acetic acid (0.6% in water, i.p.) by 49.9%, 63.7% and 43.8%, respectively. The aqueous extract (200 and 400 mg/Kg, p.o.) reduced formalin (1%) effects only at the second phase of the experiment by 49.3% and 53.7%, respectively. Naloxone (5 mg/Kg, i.p.) was not able to revert the extract effect, however caffeine (10 mg/Kg, i.p.) reverted its effect by 19.8% at the second phase of the formalin test. The aqueous extract (200 mg/Kg, p.o.) inhibited edema by 12.9% when we used the rat paw edema model. The acute toxicity was low in mice. CONCLUSION: The T. avellanedae inner bark aqueous extract presented antinociceptive and antiedematogenic activities at the used models, with a possible antinociceptive effect associated to the adenosine system.