Anti-inflammatory, antinociceptive effects and involvement of opioid receptors in the antinociceptive activity of Eugenia uniflora leaves obtained with water, ethanol, and propylene glycol mixture

Abstract

Ethnopharmacological relevanceEugenia uniflora (Myrtaceae) is a species native to Brazil and has a traditional use in the treatment of inflammation. Aim of the studyTo evaluate the anti-inflammatory and antinociceptive effects, and the involvement of opioid receptors in the antinociceptive activity of extract and fractions from Eugenia uniflora leaves. Materials and methodsTLC and HPLC were used to characterize the spray-dried extract (SDE) and fractions. In the in vivo assays, Swiss (Mus musculus) mice were used. Carrageenan-induced hind-paw edema and carrageenan-induced peritonitis models were used to determine the anti-inflammatory effect of the extract (50, 100, or 200 mg/kg). Acetic acid-induced writhing, tail-flick, and formalin tests were used to determine the antinociceptive effect of the extract (50, 100, or 200 mg/kg). The aqueous (AqF) and ethyl acetate (EAF) fractions (6.25, 12.5, and 25 mg/kg) were then combined with naloxone to evaluate the involvement of opioid receptors in the antinociceptive activity. ResultsIn this work, the TLC and HPLC analysis evidenced the enrichment of EAF, which higher concentration of gallic acid (5.29 ± 0.0004 %w/w), and ellagic acid (1.28 ± 0.0002 %w/w) and mainly myricitrin (8.64 ± 0.0002 %w/w). The extract decreased the number of total leukocytes and neutrophils in the peritoneal cavity (p < 0.05), at doses of 100 and 200 mg/kg and showed significant inhibition in the increase of paw edema volume (p < 0.05). The treatment per oral route (doses of 50, 100, and 200 mg/kg) significantly reduced the nociceptive response in acetic acid-induced abdominal writhing (p < 0.05). The effect of the extract on the tail-flick test showed a significant increase in latency time of animals treated at doses of 200 and 100 mg/kg (p < 0.05). The extract and ethyl acetate fraction reduced the nociceptive effect in both phases of formalin at all tested doses. The naloxone reversed the antinociceptive effect of EAF, suggesting that opioid receptors are involved in mediating the antinociceptive activity of EAF of E. uniflora in the formalin test. ConclusionThe current study demonstrates the anti-inflammatory and analgesic activities of water: ethanol: propylene glycol spray-dried extract from E. uniflora leaves using in vivo pharmacological models in mice. Our findings suggest that spray-dried extract and ethyl acetate fraction exhibit peripheral and central antinociceptive activity with the involvement of opioid receptors that may be related to the presence of flavonoids, mainly myricitrin.