shihulimonin-a and Pain

The antinociceptive effect of the limonexic acid isolate of Raulinoa echinata Cowan in four models of pain in mice is described. When evaluated against acetic acid-induced abdominal constrictions, limonexic acid (10, 30 and 60 mg kg(-1), i.p.) produced dose-related inhibition of the number of constrictions, with a mean ID50 value of 43 (2.3-79) micromol kg(-1), and was more potent than some standard drugs. In the formalin test, limonexic acid inhibited both the first and second phases of formalin-induced pain. Furthermore, the effect was more pronounced in the second phase, with a mean ID50 value of 13.66 (9.35-19.61) micromol kg(-1), and had a pharmacological profile that was similar to standard drugs such as acetaminophen and acetyl salicylic acid. Limonexic acid also produced dose-related inhibition of glutamate- and capsaicin-induced pain, with mean ID50 values of 11.67 (8.51-16.0) micromol kg(-1) and 47.17 (36.51-60.93) micromol kg(-1), respectively. The mechanism of action is not completely understood, but seems to involve direct interaction with the GABAergic and nitroxidergic pathways.

Topics: Acetaminophen; Analgesics; Animals; Aspirin; Disease Models, Animal; Dose-Response Relationship, Drug; gamma-Aminobutyric Acid; Inhibitory Concentration 50; Limonins; Male; Mice; Nitrergic Neurons; Pain; Pain Measurement; Phytotherapy; Plant Extracts; Plant Roots; Plant Stems; Rutaceae