Ação anti-helmíntica in vitro e modificações ultraestruturais em Haemonchus contortus induzidas por uma fração alcaloídica de Annona tomentosa

Abstract

The alkaloids, secondary metabolites of plants, exhibit diverse bioactivities, including anthelmintic effects. Considering the resistance of nematodes to most commercial drugs, the investigation of natural products with anthelmintic properties becomes increasingly relevant for the development of new anthelmintic drugs. Among the nematodes affecting sheep and goats, Haemonchus contortus stands out due to its high prevalence and pathogenicity in tropical and subtropical regions. This study aimed to obtain an alkaloidal fraction (Alk.F) from Annona tomentosa and evaluate its in vitro anthelmintic activity as well as its hemolytic activity. Alk.F was obtained from the methanolic extract of the stem bark of A. tomentosa. The detection and identification of alkaloids in Alk.F were performed through thin-layer chromatography and

high-performance liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI- IT-MS), respectively. The evaluation of Alk.F's in vitro anthelmintic activity on H. contortus

larvae was conducted through artificial exsheathment and larval development assays. Changes in the ultrastructure of H. contortus L3 larvae induced by Alk.F were assessed through atomic force microscopy. The in vitro hemolytic activity of Alk.F was evaluated by measuring the lysis of sheep erythrocytes. Among the nine predominant peaks obtained, seven alkaloids were identified in Alk.F: reticuline, reticuline N-oxide, reticuline N-oxide isomer, cyclanoline, asimilobine, tetrahydropalmatine, and anonaine. Alk.F exhibited low hemolytic activity, with only 2.7% hemolysis at 0.5 mg/mL. Additionally, it inhibited larval development and exsheathment, with 50% inhibitory concentrations (IC50) of 0.026 mg/mL and 0.36 mg/mL, respectively. At a concentration of 0.026 mg/mL, Alk.F induced changes in the cuticle of H. contortus larvae, resulting in reduced adhesion and increased height. In conclusion, Alk.F demonstrates in vitro activity against H. contortus larvae, disrupting the cuticle structure, and holds potential for the development of new strategies to control this nematode.