Chemical composition and antinociceptive effect of aqueous extract from Rourea induta Planch. leaves in acute and chronic pain models

Ethnopharmacological relevanceRourea induta Planch. is a small tree or shrub growing wild in Brazil and belonging to the Connaraceae family. It is used for the treatment of Chagas disease and as antirheumatic in folk medicine. This study was designed to investigate the antinociceptive activity of the aqueous extract (AERi) of Rourea induta leaves in rodents, as well as isolate and identify components that can be responsible for its effect.Material and methodsThe antinociceptive effect of orally administered AERi was evaluated in behavioral models of acute (formalin) and chronic [complete Freund׳s adjuvant (CFA)] pain in mice. We also investigated the possible involvement of opioid receptors and proinflammatory cytokines (interleukin-1β and tumor necrosis factor-α) in the antinociceptive effect of the AERi. In addition, a nonspecific effect of AERi was evaluated by measuring locomotor activity and corporal temperature. Finally, we performed a phytochemical analysis of AERi.ResultsHPLC titration revealed the presence of hyperin (21.6 mg/g), quercetin-3-O-β-xyloside (4.4 mg/g), quercetin-3-O-α-arabinofuranoside (12.0 mg/g), and quercetin (2.1 mg/g). It was also possible to isolate minor constituents׳ chlorogenic acid, neochlorogenic acid and procyanidin C1. The oral administration of AERi (100 mg/kg) significantly inhibited the neurogenic (37±5%) and inflammatory (34±7%) phases of formalin-induced pain. Acute and repeated treatment of animals with AERi (100 mg/kg, p.o.) once a day markedly reduced the mechanical hypersensitivity response induced by CFA, and this effect was evident until the day 10. Moreover, repeated treatment with AERi (100 mg/kg, p.o.) significantly reduced the levels of IL-1β and TNF-α in the paw (22±7% and 50±19%) and in the spinal cord (100% and 100%) when compared to the CFA group. The AERi (100 mg/kg, p.o.) markedly reduced biting behavior induced by intrathecal injection of TNF-α (81±11%). Finally, the effect of AERi was not associated with changes in locomotor activity or the corporal temperature of animals.ConclusionThese data show that aqueous extract of Rourea induta has significant antinociceptive action, which seems to be associated with an inhibition of pro-inflammatory cytokines activated pathways. These findings support the ethnomedical uses of this plant.

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