Antipyretic and antinociceptive properties of Mentha longifolia Huds. (Lamiaceae) leaf aqueous extract in rats and mice.

The antipyretic and antinociceptive properties of Mentha longifolia Huds. (Lamiaceae) leaf aqueous extract were investigated using lipopolysaccharide (LPS)-induced pyrexia in rats, and acetic acid and hot plate analgesia tests in mice. Pentoxifylline, paracetamol and morphine were used as standard drugs for comparison. M. longifolia leaf aqueous extract and pentoxifylline (37.5-150 mg/kg i.p.) significantly (P < 0.05-0.02) reduced the LPS (50 g/kg i.m.)-elicited pyrexia. Pentoxifylline (50 mg/kg i.p.) also significantly (P < 0.01) reduced LPS (50 g/kg i.m.)-induced pyrexia. M. longifolia leaf aqueous extract (6.25-100 mg/kg i.p.) and paracetamol (500 mg/kg i.p.) profoundly inhibited the writhes produced by 3% acetic acid. Furthermore, the plant extract (25-400 mg/kg i.p.) and morphine (10 mg/kg i.p.) significantly (P < 0.001) delayed the hot plate reaction time in mice. The LD(50) values for oral and intraperitoneal administration of the plant extract were > 3200 mg/kg and 1730 mg/kg, respectively. Phytochemical analysis revealed the presence of flavonoids, saponins, tannins, reducing sugars, cardiac glycosides and triterpene steroids in the leaves of M. longifolia. These data indicate that M. longifolia leaf aqueous extract has antipyretic and antinociceptive properties. Furthermore, the relatively high LD(50) values obtained for oral and intraperitoneal administration of the plant extract demonstrate that the plant extract is non-toxic to mice.