Síntese e avaliação da atividade anti-Trypanosoma cruzi de novos derivados de licarina A: estudos in silico, in vitro e in vivo

Abstract

Chagas disease, a neglected tropical disease, affects mainly Latin America and is caused by the flagellate protozoan Trypanosoma cruzi, which lives and reproduces in different cells and tissues. The signs and symptoms of this disease are quite variable, being characterized by having an acute phase and a chronic phase, the latter related to the most serious effects of the disease, leading to serious complications and often death. Drugs for the treatment of the disease are scarce, with benznidazole being the one of choice, which acts mainly in the acute phase and has significant adverse effects. In this sense, the need to discover new trypanocidal drugs is imperative and natural products are potential sources in this context. Neolignans are secondary metabolites found in certain plant species and one of their representatives, licarin A, exerts several well-reported biological activities, including trypanocide. Thus, it represents a promising substance as a starting point for the development of optimized trypanocidal agents. With this in mind, the objective of this work was the synthesis and biological evaluation of derivatives of licarin A, with a view to discovering more active and less toxic trypanocidal products, in order to collaborate with the discovery of a new agent against the T. cruzi. Licarin A was obtained by a biosynthetic method using isoeugenol, coconut water (Cocos nucifera L.) and hydrogen peroxide. Subsequently, structural modifications were carried out, mainly directed to the phenolic hydroxyl of licarin A (via etherification reactions) and its propenyl chain (via oxidation reactions). The final products were obtained in suitable yields to the objetives with this work and were characterized by the usual spectroscopic and spectrometric methods. Afterwards, they were submitted to an in vitro evaluation of their trypanocidal potential against different evolutionary forms of the parasite, in addition to cytotoxicity in Vero ® cells. Only lycarin A and derivatives with modifications in the propenyl side chain had good results in the anti- epimastigote assay and, therefore, They both were evaluated against amastigote and trypomastigote forms. In these tests, the dihydroxy derivative DL07 was the most active compound, which presented an IC 50 value of 1.23 µg.mL -1 against amastigote forms. In view of these results, this compound and licarin A, for comparision, were used for in vivo tests in mice pre-infected with T. cruzi, in which it was possible to notice an important reduction in parasitemia in animals treated with DL07 at a dose of 100 mg.kg -1 . In addition to this in vivo antiparasitic effect, a longer survival rate was observed in animals treated with DL07 than in those submitted to licarin A, indicating its lower toxicity compared to the precursor. Additionally, molecular docking studies of the substances synthesized with the enzyme trypanothione reductase, an important molecular target in the search for new agents against T. cruzi, were carried out, and it was found that DL07 was the compound that showed the most stable interaction with this enzyme. The computational results obtained showed that the presence of a dihydroxylated side chain instead of the propenyl group and the 4- chloro benzyl group as a substitute in the licarin A phenol are important points for interaction with the active site of the enzyme under study. Additional computational studies to predict physicochemical and pharmacokinetic properties also pointed out that the DL07 derivative has a good probability of being absorbed by the gastrointestinal tract and not crossing the blood-brain barrier, in addition to not having any region of its structure that has a negative impact on the activity. Thus, it was found in this study that the dihydroxy derivative DL07 is superior to licarin A as a trypanocidal agent, as well as in terms of safety. Associated with good in silico interaction profiles with trypanothione reductase and physicochemical and pharmacokinetic properties, DL07 is defended as an excellent prototype for future chemical-medicinal studies with a view to discovering new candidates for trypanocidal drugs.