Efeito anti-inflamatório tópico associado à atividade antioxidante do extrato aquoso das folhas da Annona muricata L

Abstract

Annona muricata L., also known as "soursop", is popularly used to treat diseases related to inflammatory and oxidative processes. In addition, the scientific literature investigates the biological effects of different parts of this medicinal plant. However, the anti-inflammatory effect of the aqueous extract of its leaves via topical administration still needs to be better elucidated. In this context, the objective of this study was to investigate the effect of topical application of the aqueous extract of the leaves of A. muricata L. (AEAM) in acute model of skin inflammation and evaluation of the role of its antioxidant activity. In vitro experiments were performed to quantify total phenolic compounds and flavonoids; characterization of phenolic compounds by HPLC; AEAM antioxidant capacity tests (12.5, 25, 50, 100 and 200 μg/mL) by eliminating the radicals 2,2-diphenyl-1-picryl-hydrazil (DPPH) and nitric oxide (NO), inhibition of lipidic peroxidation and analysis of the iron-reducing potential (FRAP). In addition, cell viability and the release of reactive oxygen species (ROS) tests were developed in L929 fibroblasts. In the in vivo experiments, after the approval of the Animal Research Ethics Committee at UFS (nº 9256010719), the topical anti-inflammatory activity of AEAM (0.3, 1 and 3 mg/ear) was evaluated in the model of ear edema induced by 12-O-tetradecanoil-phorbol-13-acetate (TPA) (1 μg/ear, vehicle) in male Swiss mice. Dexamethasone (0.05 mg/ear, control) was used as a standard treatment. After 6 hours, the edema of ear biopsies, myeloperoxidase activity (MPO), histological changes and oxidative parameters were measured. The results were expressed as mean ± SEM and the statistical evaluation of the data was performed using one-way ANOVA followed by the Tukey test, with p<0.05 considered significant. The amount of total phenolics in the EAAM was 164.52±1.13 mg of gallic acid equivalent/g of extract and the amount of total flavonoids was 77.02±0.01 mg of catechin equivalent/g of extract. In the HPLC analysis, five phenolic compounds were identified: quercetin 3-glycoside, rutin, chlorogenic acid, catechin and gallic acid. In antioxidant tests, we observed a reduction in the DPPH radical (IC50=97.1 μg/mL) and NO (IC50=44.1 μg/mL), as well as an increase in the iron-reducing potential and reduction of spontaneous (IC50=122.8 μg/mL) and induced (IC50=401.5 μg/mL) lipid peroxidation. In L929 fibroblasts, AEAM did not alter cell viability, but it reduced ROS release (p<0.01). Topical treatment with EAAM promoted a decrease in ear edema (p<0.001; 1 and 3 mg/ear), myeloperoxidase activity (p<0.001; 1 and 3 mg/ear) and inflammatory histological parameters, represented by the lower number of leukocytes (p<0.001; 3 mg/ear) and lesser dermis thickness (p<0.001; 3 mg/ear) compared to the vehicle group. In addition, a reduction in total hydroperoxides (p<0.05) and modulation of catalase (p<0.05; 3 mg/ear) was observed, but there was no change in the enzymatic activity of superoxide dismutase (SOD). Thus, these results indicate a potential topical anti-inflammatory effect of A. muricata L. associated with the antioxidant capacity suggested by the action of phenolic compounds present in the aqueous extract of its leaves.