A Dual In vitro and In silico Approach to Evaluate 1,4-Naphthoquinone-1,2,3-triazole Hybrids Against Atovaquone-Resistant Malaria

Malaria continues to pose a major global health burden affecting millions annually. Despite advancements in treatment, the emergence of drug-resistant Plasmodium strains has undermined current treatment strategies, including atovaquone. Atovaquone is a key mitochondrial inhibitor targeting the cytochrome bc1 (cyt bc1) complex, with resistance primarily driven by mutation in the cytochrome b gene. Moreover, atovaquone’s reliance on a single target site and its pharmacokinetic limitations further underscore the urgent need for alternative drugs. To address these challenges, this dual in vitro and in silico study evaluated ten 1,4-naphthoquinone-1,2,3-triazole hybrids targeting atovaquone-resistant (FCR3) P. falciparum. Molecular modelling studies were performed on Saccharomyces cerevisiae (PDB ID 3CX5), involving the building of a mutant model to simulate the Y279S mutation (equivalent to Y268S mutation in P. falciparum), in order to rationalise the observed results. Additionally, pharmacokinetic properties and drug-likeness of these hybrids were predicted in silico. Hybrids D12 and D13 exhibited strong antiplasmodial activities, 61- and 52-fold, respectively, more than atovaquone. Molecular modelling studies indicated a strong correlation between in silico and in vitro activities by displaying binding interactions between the ligand and the mutant model. Structure-activity relationships (SAR) analysis identified key structural features essential for favourable binding interactions with target binding site residues. Furthermore, in silico evaluations of these hybrids suggested good oral bioavailability and high gastrointestinal absorption, with no significant risk of severe toxicity. Hybrids D12 and D13 exhibit potential as lead candidates, with their strong in vitro efficacy well-supported by in silico data, warranting further optimisation and development.