Analgesic effect of aqueous extract of Olea europaea L. in experimental models of pain in male rat

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Abstract

The medicinal plant Olea europaea L. is a valuable one whose fruit and its oil are considered as food. There are some reports in ancient medical literature that aqueous extract of its leaves has analgesic effects. This prompted us to investigate the analgesic effect of aqueous extract of its leaves using formalin and tail-flick tests. For this purpose, male NMRI rats weighting 220-260 g were used in all experiments. The aqueous extract of this plant was intraperitoneally injected at doses of 200, 400, and 600 mg/kg. In this study, sodium salicylate (300 mg/kg) and distilled water were used as positive and negative controls respectively. The results obtained were analyzed using one-way ANOVA and Tukey-Kramer tests. Our data showed that intraperitoneal injection of aqueous extract of the leaves of this plant (200, 400, and 600 mg/kg) produces a significant analgesia in both phases of the formalin test (P<0.001). Meanwhile, different doses of this plant did not produce any analgesic effect in tail-flick test. On the other hand, sodium salicylate (300 mg/kg, i.p.) induced analgesia in the second phase of the formalin test. Aqueous leaf extract of Olea europaea at doses of 200, 400, and 600 mg/kg had a more potent anti-nociceptive effect in comparison with sodium salicylate (300 mg/kg, i.p.) in formalin test. Since the aqueous extract of Olea europaea l. exert analgesic effects in both phases of the formalin test. Therefore, it may be concluded that it produces anti-nociception through the central mechanisms. In this respect, flavonoid and steroid compounds of the plant may be involved in its anti-nociceptive effects in rats.