Evaluation of the antinociceptive, anti-inflammatory and antipyretic activities of Ruta Graveolens L. in mice and rats

Abstract

Evaluation of the antinociceptive, anti-inflammatory and antipyretic activities of Ruta graveolens L. in mice and rats FIRDOWS LOONAT M. Pharm. Pharmaceutical Sciences thesis: School of Pharmacy, University of the Western Cape Ruta graveolens (Rutaceae) L. is a medicinal plant that is commonly used to manage and treat essential events such as pain, inflammation and fever. Despite its popularity, particularly as a medicinal plant in the Calvinia district and Bredasdorp region of South Africa, scientific data to substantiate its widespread traditional use and the possible mechanisms of action for this plant species is lacking. Therefore, the objectives of this study were: to scientifically evaluate and validate the antinociceptive, anti-inflammatory and antipyretic activities of Ruta graveolens using the acetic-acid writhing test and hot-plate test, the carrageenan rat paw oedema test, and the E. coli-induced pyrexia test, respectively; to investigate the possible mechanisms of the antinociceptive, anti-inflammatory and antipyretic activities of the plant using interaction studies; to determine some secondary metabolites present in the plant species using standard phytochemical analytical procedures; to characterise the plant species using HPLC techniques; and to determine the safety profile of the plant species using an acute toxicity study.Three percent (3 %) acetic acid (0.25 ml, i.p.) produced a substantial number of writhes in mice. The leaf methanol extract of Ruta graveolens (100 mg/kg, i.p.) significantly reduced the number of writhes induced by 3 % acetic acid (0.25 ml, i.p.). R. graveolens (100 mg/kg,i.p.) produced 54 % inhibition of 3 % acetic acid-induced writhes. Indomethacin (20 mg/kg,i.p.) and paracetamol (500 mg/kg, i.p.) significantly reduced the number of 3 % acetic acidinduced writhes. Indomethacin (20 mg/kg, i.p.) and paracetamol (500 mg/kg, i.p.) produced 57 % and 80 % inhibition of 3 % acetic acid-induced writhes, respectively. R. graveolens (25– 50 mg/kg, i.p. and 200 – 400 mg/kg, i.p.) and indomethacin (10 mg/kg, i.p.) did not significantly reduce the number of writhes induced by 3 % acetic acid. However, combined therapy of the leaf methanol extract of R. graveolens (25 mg/kg, i.p.) and indomethacin (10 mg/kg, i.p.) significantly reduced the number of 3 % acetic acid-induced writhes. The combined therapy of the lowest and sub-effective doses of the leaf methanol extract of R. graveolens (25 mg/kg, i.p.) and indomethacin (10 mg/kg, i.p.) produced 59 % inhibition of the writhes elicited by 3 % acetic acid. The leaf methanol extract of R. graveolens (50 – 400 mg/kg, i.p.) greatly delayed the reaction time in mice to thermal stimulation produced with hot-plate. 50 – 400 mg/kg (i.p.) of the leaf methanol extract of R. graveolens significantly antagonised rat paw oedema induced by 1 % carrageenan (0.1 ml, subplantar) over the 4 h period of testing. In addition, indomethacin (10 mg/kg, i.p.) significantly antagonised 1 % carrageenan-induced rat paw oedema. R. graveolens (25 mg/kg, i.p.) and indomethacin (2mg/kg, i.p.) given separately did not significantly alter rat paw oedema induced by 1 % carrageenan. However, combined therapy of the leaf methanol extract of R. graveolens (25 mg/kg, i.p.) and indomethacin (2 mg/kg, i.p.) significantly reduced 1 % carrageenan-induced rat paw oedema. The leaf methanol extract of R. graveolens (400 mg/kg, i.p.) significantly reduced the mean rectal temperature of normothermic rats. Ruta graveolens (100 – 400 mg/kg, i.p.) significantly reduced pyrexia induced by E. coli (50 μg/kg, i.m.) over the 5 h period of testing. In addition, pentoxifylline (50 mg/kg, i.p.) significantly reduced E. coliinduced pyrexia. Ruta graveolens (25 – 50 mg/kg, i.p.), paracetamol (500 mg/kg, i.p.) and pentoxifylline (10 mg/kg, i.p.) did not significantly reduce pyrexia induced by E. coli.However, combined therapy of the leaf methanol extract of R. graveolens (25 mg/kg, i.p.)and pentoxifylline (10 mg/kg, i.p.) significantly reduced E. coli (50 μg/kg, i.m.)-induced pyrexia.The phytochemical studies of the powdered leaves of Ruta graveolens indicated the presence of alkaloids, cardiac glycosides, flavonoids, saponins, tannins and triterpene steroids. The HPLC fingerprint indicated characteristic peaks at the following retention times; 1.654 min,2.271 min, 2.403 min, 4.705 min and 7.691 min. The LD50 obtained for Ruta graveolens after oral administration was probably greater than 4000 mg/kg which shows that the plant extract is non-toxic to mice.In conclusion, the data obtained indicate that Ruta graveolens possesses antinociceptive, antiinflammatory and antipyretic activities. Since prostaglandins have been shown to mediate acetic acid-induced writhes, prostaglandins, histamine, serotonin, capsaicin and bradykinin implicated in carrageenan-induced rat paw oedema, and tumor necrosis factor-α (TNF-α) implicated in E.coli-induced pyrexia, it is possible that R. graveolens may be producing its antinociceptive, anti-inflammatory and antipyretic activities by affecting these chemical mediators. The data obtained also justify the use of the plant species by traditional medicine practitioners for the treatment of painful and inflammatory conditions, and pyrexia.