Evaluation Of Writhing And Paw Edema In Swiss Male Mice Of Sesquiterpene Lactones Fraction Obtained From Artemisia annua L.

Introduction: Artemisia annua L. is known for antimalarial properties. The artemisinin production process generates high yields of sesquiterpene lactones fraction (1,72% artemisinin) by-products. In order to enable to access the pharmacological potency of the fraction an antiinflamatory experimental model was evaluated on writhing and paw edema assay induced by carrageenan in Swiss male mice. Methods: In both tests groups of Swiss mice (n = 6) were treated i.p with vehicle (10 ml/kg) and sesquiterpene lactones sample using 100, 300, and 500 mg/kg (i.p.) doses. Writhings were induced by an i.p. injection of 0.8% acetic acid solution (10 ml/kg), 30 min after treatment. After this injection, the numbers of writhings (abdominal constrictions) were cumulatively counted over 15 min, for nociception evaluation. For assessment of edema, 25µL of a 3% solution carrageenan were injected subcutaneously into the plantar region of the left hind paw. Paw measurements (plethysmometer) were taken at 2, 4, 6 and 24hours. Results: Values are expressed as mean ± standard error. Data were analyzed by analysis for variance (ANOVA) and Tukey's test. In the writhing test values obtained were G1 (control) 48 ± 5,2; G2 (500 mg/kg) 9,5 ± 3,23; G3 (300 mg/kg) 31,5 ± 3,5; G4 (100 mg/kg) 48,5 ± 7,58). P < 0,05 G1 vs. G2, G2 vs. G3, G2 vs. G4. Paw edema induced by carrageenan are shown in the graph (Figure 1)

Fig. 1: Evaluation of different doses of sesquiterperne lactones fraction on inflammatory response post-carrageenan injection

Conclusions: In the writhing test the 500 mg/kg dose sesquiterpene lactones fraction proved to be the most effective in reducing abdominal constrictions, possibly by a nociceptive mechanisms. In the assessment of paw edema after 2 hours at 500 and 300 mg/kg doses proved to be more effective than the positive control, and this profile was maintained for up to 4 hours, suggesting an anti-inflammatory property of the sample. Further tests are needed to confirm these properties.