Artemisinin and deoxyartemisinin isolated from Artemisia annua L. promote distinct antinociceptive and anti-inflammatory effects in an animal model

Abstract

Artemisia annua L., known for antimalarial activity, has demonstrated evidence of anti-inflammatory potential. Previously our research group reported the anti-inflammatory and antinociceptive effect of a sesquiterpene lactone-enriched fraction (Lac-FR) obtained from plant, containing artemisinin and deoxyartemisinin. Both the isolated compounds and Lac-FR evaluated on experimental animal models, in the formalin test showed that deoxyartemisinin reduced both neurogenic pain (56.55 %) and inflammatory pain (45.43 %). These findings were superior to the effect of artemisinin (reduction of 28.66 % and 33.35 %, respectively). In the tail flick test, the antinociceptive effect reported as a percentage of the maximum possible effect (%MPE), deoxyartemisinin showed a lower antinociceptive effect (41.57 %) compared to morphine (75.94 %) in 0.5 h. After 1.5 h, the MPE of deoxyartemisinin (87.99 %) exceeded the effect of morphine (47.55 %), without reversal with naloxone. The MPE of artemisinin (23.3 %) observed after 2 h was lower than deoxiartemisinin, without reversal with the opioid antagonist. Lac-FR and artemisinin demonstrated reductions in ear edema of 43.37 % and 48.19 %, respectively, higher than the effect of deoxyartemisinin (33.64 %). Artemisinin reduced tumor necrosis factor alpha (TNF-α) (76.96 %) more selectively when compared to interleukin-1beta (IL-1β) (48.23 %) and interleukin-6 (IL-6) (44.49 %). Lac-FR showed greater selectivity in IL-6 reduction (56.49 %) in relationship to TNF-α (46.71 %) and IL-1β (45.12 %), whereas deoxyartemisinin selectively reduced TNF-α (37.37 %). The results of our study indicate that the lactones isolated did not have relationship with the opioid system. Deoxyartemisinin showed a higher antinociceptive potential than artemisinin. Whereas, artemisinin showed a higher reduction of inflammation and mediators, with a better anti-inflammatory activity outcome.

Keywords: Anti-inflammatory; Antinociceptive; Artemisia annua L.; Edema; Pain; Sesquiterpene lactones.