Computational Design of Novel Allosteric Inhibitors for Plasmodium falciparum DegP.

The serine protease, DegP exhibits proteolytic and chaperone activities, essential for cellular protein quality control and normal cell development in eukaryotes. The P. falciparum DegP is essential for the parasite survival and required to combat the oscillating thermal stress conditions during the infection, protein quality checks and protein homeostasis in the extra-cytoplasmic compartments, thereby establishing it as a potential target for drug development against malaria. Previous studies have shown that diisopropyl fluorophosphate (DFP) and the peptide SPMFKGV inhibit E. coli DegP protease activity. To identify novel potential inhibitors specific to PfDegP allosteric and the catalytic binding sites, we performed a high throughput in silico screening using Malaria Box, Pathogen Box, Maybridge library, ChEMBL library and the library of FDA approved compounds. The screening helped identify five best binders that showed high affinity to PfDegP allosteric (T0873, T2823, T2801, RJC02337, CD00811) and the catalytic binding site (T0078L, T1524, T2328, BTB11534 and 552691). Further, molecular dynamics simulation analysis revealed RJC02337, BTB11534 as the best hits forming a stable complex. WaterMap and electrostatic complementarity were used to evaluate the novel bio-isosteric chemotypes of RJC02337, that led to the identification of 231 chemotypes that exhibited better binding affinity. Further analysis of the top 5 chemotypes, based on better binding affinity, revealed that the addition of electron donors like nitrogen and sulphur to the side chains of butanoate group are more favoured than the backbone of butanoate group. In a nutshell, the present study helps identify novel, potent and Plasmodium specific inhibitors, using high throughput in silico screening and bio-isosteric replacement, which may be experimentally validated.

Fabrication of Mupirocin-Loaded Nanostructured Lipid Carrier and Its In Vitro Characterization.

In the present study, mupirocin (MP), an antimicrobial agent, was formulated as a nanostructured lipid carrier (NLC) by using a novel method named as melt emulsion ultrafiltration method. For the formulation of NLC, glyceryl monostearate and watermelon seed oil were used as solid and liquid lipids, respectively. The method was optimized for various parameters by Taguchi design of experiment and prepared NLCs were characterized for particle size, polydispersity index (PDI), shape, zeta potential, % drug loading, and in vitro release profile. The optimized NLCs were found to be smooth, monodisperse with PDI 0.229 ± 0.093. NLCs were found to have an average particle size of 139 ± 0.75 nm and +21.9 ± 0.98 mV as zeta potential. The % drug loading of optimized NLCs was found to be 59% ± 0.13%. The optimized NLCs were able to release the drug up to 24 h. The release kinetic study revealed mixed-order kinetics. Hence, it was concluded that the novel method is simple and able to fabricate MP-loaded NLCs with sustained release property and being stable in terms of particle size, PDI, and % drug loading.

High throughput in silico identification and characterization of Plasmodium falciparum PRL phosphatase inhibitors.

Kinases and phosphatases are involved in many essential processes in Plasmodium lifecycle. Among the identified 67 Plasmodium falciparum phosphatases, Phosphatase of Regenerating Liver (PRL) family protein homolog, PfPRL, is an essential parasite tyrosine phosphatase. PfPRL is shown to be prenylated, secreted, and involved in the host invasion process. In the present study, a structure-based high throughput in silico screening of PfPRL binders, using ChEMBL-NTD compounds lead to the identification of nine compounds based on binding energy, Lipinski rule of five, and QED score. The most of the shortlisted compounds are known to inhibit parasite growth at a concentration (EC50) ≤2 µm in in vitro P. falciparum culture assays. MD simulations were carried out on the shortlisted nine potential enzyme-inhibitor complexes to analyze specificity, stability, and to calculate the free binding energies of the complexes. The study identifies PfPRL as one of the potential drug targets for selected ChEMBL-NTD compounds that may be exploited as a scaffold to develop novel antimalarials.