Atividade anti-inflamatória e antinociceptiva do extrato metanólico das folhas de Annona squamosa e da sua substância isolada, palmatina

Abstract

Inflammation and the pain, a cardinal sign of the former, are complex processes involving multiple signaling pathways and cell types. Its deregulation, however, serves as a basis for the development of different types of diseases and causes a considerable burden on health systems. Moreover, the pharmacological treatment for inflammation and pain has several severe side effects. Considering the need of developing new medicines, the study of pharmacological properties from medicinal plants and their isolated substances could be a good option. The leaves, or the entirety of Annona squamosa, also popularly known as custard apple, pine cone, custard apple, or, seetha pazham, are used by the population to treat pain and arthritis. Furthermore, palmatine, an alkaloid isolated from A. squamosa leaves contains several pharmacological effects already described in scientific literature. Its antiinflammatory and analgesic potential, however, has not yet been fully elucidated. Considering this information, this paper aimed to evaluate the analgesic (anti-nociceptive and antihyperalgesic), antiarthritic and anti-inflammatory effect, through animal models of inflammation, related to nociception and hyperalgesia, and the leukocyte viability, in vitro, of the methanolic extract from Annona squamosa leaves and palmatine. In order to achieve the goal, at first, the A. squamosa methanolic extract was prepared and submitted to a chemical analysis (chemical profile and presence of alkaloids), through ultra-high performance liquid chromatography with electrospray ionization coupled to sequential mass spectrometry (UHPLC -ESI-MS/MS). In addition, EMAS (30, 100 and 300 mg/kg) and palmatine (0.3, 1 and 3 mg/kg) were administered orally in the carrageenan-induced pleurisy test where leukocyte migration, protein extravasation and Nitric Oxide (NO) levels were analyzed. EMAS (100 mg/kg) and palmatine (1 mg/kg), administrated orally, were tested in zymosaninduced arthritis (joint inflammation) and in formalin models. Furthermore, the animals were treated with 3 and 30 pg/paw of palmatine, to evaluate this substance's actions on the mechanical hyperalgesia induced by tumor necrosis factor (TNF), 3 and 4 hours after the application of this cytokine. Leukocytes viability treated with EMAS and palmatine was evaluated in vitro using MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium) test. Among these tests results, the analysis of the chemical profile. In carrageenan-induced pleurisy, treatment with EMAS (100 and 300 mg/kg) and palmatine (1 and 3 mg/kg) significantly inhibited leukocyte migration and NO production. EMAS and palmatine inhibited parameters (mechanical hyperalgesia, leukocyte migration and edema) of zymosaninduced joint inflammation. In the formalin test, EMAS (100 mg/kg) and palmatine (1mg/kg) inhibited mechanical and cold hyperalgesia. Moreover, palmatine reduced the nociception of formalin test's second phase (inflammatory phase). Through palmatine's intraplantar treatment (3 and 30 pg/paw), mechanical hyperalgesia was inhibited 3 and 4 hours after tumor necrosis factor (TNF) administration. Therewithal, EMAS and palmatine did not show cytotoxicity in vitro. Considering these results, it can be concluded that EMAS and palmatine have analgesic, anti-arthritic and anti-inflammatory effects, which may partly explain this plant's popular use in pain and arthritis treatments.