Avaliação do potencial antimicobacteriano da Caulerpina e seus derivados em modelos in silico e in vitro

Abstract

Human tuberculosis (TB) is an infectious disease caused mainly by Mycobacterium tuberculosis (Mtb), a pathogenic, micro-aerophilic bacterium that commonly affects the lungs and is one of the most infectious diseases in the world. Due to the emergence of resistant bacterial strains, TB is still a particularly challenging disease, a fact attributed mainly to poor adherence to treatment protocols, spontaneous mutations in the genome of these microorganisms, and drug side effects. Thus, continuous efforts are needed for the discovery and development of new anti-TB drugs. The marine environment is a valuable source of diverse natural products. The chemical diversity of its molecules has provided the discovery of many novel products, among them caulerpine, the major substance of the species Caulerpa racemosa, a bis-indolic alkaloid, with proven antioxidant, antifungal, antispasmodic, antinociceptive, anti-inflammatory, antiviral, and leishimanicidal biological activity. According to the pharmacological potential of this molecule, studies have been conducted to develop analogues by the introduction of new substituents, which resulted in significant chemical differences and different pharmacokinetic properties. The present work aimed to synthesize and evaluate the antimycobacterial potential of PLC and its derivatives in Mtb models, through in silico and in vitro studies, as an initial step towards the development of prototype drug candidates for TB treatment. Therefore, molecular modeling studies were performed using Mtb target proteins and as ligands the indolic alkaloid CLP and its analogues, with the construction of a predictive model using in silico methodologies, followed by the isolation of CLP, synthesis of derivatives with different substituents in the ester function. In vitro tests were performed to determine the susceptibility of mycobacteria to the compounds by determining the minimum inhibitory concentration (MIC) of those with higher activity in Mtb culture and in silico evaluation of oral bioavailability and absorption, distribution, excretion and toxicity (ADMET) properties. The molecular docking study of synthetic CLP derivatives of the four proteins analyzed (DpE1, Pantothenate synthetase, Enoil-ACP reductase and Dihydrofolate reductase) showed that the synthetic CLP derivatives obtained negative energies in all enzymes under study, thus revealing that interaction occurred with all targets, highlighting the diisobutyl CLP, which showed greater affinity in the Pantothenate synthetase target. The in vitro evaluation of the most promising molecules was carried out, aiming to determine the susceptibility of mycobacteria to the compounds, finding that the diisobutyl CLP analog showed the most promising results (=125 μM). In the in silico evaluation for determination of theoretical oral bioavailability parameters, seven analogues showed promising pharmacokinetic activities and, with regard to the evaluation of theoretical ADMET, most showed good results.