Design,Synthesis, and Evaluation of Novel Ferroquine and Phenylequine Analogues as Potential Antiplasmodial Agents

7‐Chloroquinoline‐based antimalarial drugs are effective in the inhibition of hemozoin formation in the food vacuole of the Plasmodium parasite, the causative agent of malaria. We synthesized five series of ferroquine (FQ) and phenylequine (PQ) derivatives, which display good in vitro efficacy toward both the chloroquine‐sensitive (CQS) NF54 (IC₅₀: 4.2 nm ) and chloroquine‐resistant (CQR) Dd2 (IC₅₀: 33.7 nm ) strains of P. falciparum. Several compounds were found to have good inhibitory activity against β‐hematin formation in an NP‐40 detergent assay, with IC₅₀ values ranging between 10.4 and 19.2 μm .     

Adsorption to the Surface of Hemozoin Crystals: Structure-Based Design and Synthesis of Amino-Phenoxazine β-Hematin Inhibitors

In silico adsorption of eight antimalarials that inhibit β-hematin (synthetic hemozoin) formation identified a primary binding site on the (001) face, which accommodates inhibitors via formation of predominantly π-π interactions. A good correlation (r²=0.64, P=0.017) between adsorption energies and the logarithm of β-hematin inhibitory activity was found for this face. Of 53 monocyclic, bicyclic and tricyclic scaffolds, the latter yielded the most favorable adsorption energies. Five new amino-phenoxazine compounds were pursued as β-hematin inhibitors based on adsorption behaviour. The 2-substituted phenoxazines show good to moderate β-hematin inhibitory activity (<100 μM) and Plasmodium falciparum blood stage activity against the 3D7 strain. N¹,N¹-diethyl-N⁴-(10H-phenoxazin-2-yl)pentane-1,4-diamine ( P2a ) is the most promising hit with IC₅₀ values of 4.7±0.6 and 0.64±0.05 μM, respectively. Adsorption energies are predictive of β-hematin inhibitory activity, and thus the in silico approach is a beneficial tool for structure-based development of new non-quinoline inhibitors.