Abstract

In our previous work, we have demonstrated that Thymus broussonetii exerts a significant analgesic activity, which was more potent than the reference analgesic drug (acetyl salicylic acid; ASA). In this study, we examined the antinociceptive effect of three Moroccan Thyme species, i.e. Thymus satureioides, Thymus maroccanus and Thymus leptobotrys. The effect of aqueous, butanolic and ethyl acetate extracts of each species were tested on the nociceptive response in mice using a formalin test as a model of nociception. The results obtained showed that the treatment with aqueous and butanolic extracts (50, 100, 200 and 300 mg/kg, i.p.) of the three species induced a marked inhibition of the nociceptive response in both neurogenic and inflammatory phases of formalin test. The ethyl acetate extracts had a weak effect on the neurogenic phase, but it had a significant effect on the inflammatory phase. These results suggest that the aqueous and butanolic extracts act both peripherally and centrally to inhibit the nociceptive response, while the ethyl acetate extracts act rather peripherally. According to ID₅₀ values and the maximal inhibition of the nociceptive behaviour, we could conclude that T. satureioides was more potent and efficacious in inhibiting the formalin nociceptive response. Phytochemical screening carried out on these species showed the presence of quinons, saponins, tannins, terpenes and flavonoids. Our results provide evidence that T. satureioides, T. maroccanus and T. leptobotrys possess active principles that exhibit marked analgesic effect, thus confirming and justifying the popular uses of these plants to relieve some pains.

Key words: Analgesic effect, formalin test, Mice, Thymus satureioides, Thymus maroccanus, Thymus leptobotrys.