Design and synthesis of potent inhibitors of plasmepsin I and II: X-ray crystal structure of inhibitor in complex with plasmepsin II.

New and potent inhibitors of the malarial aspartic proteases plasmepsin (Plm) I and II, from the deadliest malaria parasite Plasmodium falciparum, have been synthesized utilizing Suzuki coupling reactions on previously synthesized bromobenzyloxy-substituted statine-like inhibitors. The enzyme inhibition activity has been improved up to eight times by identifying P1 substituents that effectively bind to the continuous S1-S3 crevice of Plasmepsin I and II. By replacement of the bromo atom in the P1 p-bromobenzyloxy-substituted inhibitors with different aryl substituents, several inhibitors exhibiting K(i) values in the low nanomolar range for both Plm I and II have been identified. Some of these inhibitors are also effective in attenuating parasite growth in red blood cells, with the best inhibitors, compounds 2 and 4, displaying 70% and 83% inhibition, respectively, at a concentration of 5 microM. The design was partially guided by the X-ray crystal structure disclosed herein of the previously synthesized inhibitor 1 in complex with plasmepsin II

Synthesis of malarial plasmepsin inhibitors and prediction of binding modes by molecular dynamics simulations.

A series of inhibitors of the malarial aspartic proteases Plm I and II have been synthesized with L-mannitol as precursor. These inhibitors are characterized by either a diacylhydrazine or a five-membered oxadiazole ring replacing backbone amide functionalities. Molecular dynamics simulations were applied in the design process. The computationally predicted Plm II Ki values were generally in excellent agreement with the biological results. The diacylhydrazine was found to be superior over the oxadiazole as an amide bond replacement in the Plm I and II inhibitors studied. An extensive flexibility of the S2' pocket was captured by the simulations predicting the binding mode of the unsymmetrical inhibitors. Plm I and II inhibitors with single digit nanomolar Ki values devoid of inhibitory activity toward human Cat D were identified. One compound, lacking amide bonds, was found to be Plm IV selective and very potent, with a Ki value of 35 nM

Design and synthesis of potent inhibitors of the malaria aspartyl proteases plasmepsin I and II. Use of solid-phase synthesis to explore novel statine motifs.

Picomolar to low nanomolar inhibitors of the two aspartic proteases plasmepsin (Plm) I and II, from the malaria parasite Plasmodium falciparum, have been identified from sets of libraries containing novel statine-like templates modified at the amino and carboxy terminus. The syntheses of the novel statine templates were carried out in solution phase using efficient synthetic routes and resulting in excellent stereochemical control. The most promising statine template was attached to solid support and diversified by use of parallel synthesis. The products were evaluated for their Plm I and II inhibitory activity as well as their selectivity over cathepsin D. Selected inhibitors were, in addition, evaluated for their inhibition of parasite growth in cultured infected human red blood cells. The most potent inhibitor in this report, compound 16, displays Ki values of 0.5 and 2.2 nM for Plm I and II, respectively. Inhibitor 16 is also effective in attenuating parasite growth in red blood cells showing 51% inhibition at a concentration of 5 microM. Several inhibitors have been identified that exhibit Ki values between 0.5 and 74 nM for both Plm I and II. Some of these inhibitors also show excellent selectivity vs cathepsin D

Biological and computational evaluation of resveratrol inhibitors against Alzheimer’s disease

It has been reported that beta amyloid induces production of radical oxygen species and oxidative stress in neuronal cells, which in turn upregulates β-secretase (BACE-1) expression and beta amyloid levels, thereby propagating oxidative stress and increasing neuronal injury. A series of resveratrol derivatives, known to be inhibitors of oxidative stress-induced neuronal cell death (oxytosis) were biologically evaluated against BACE-1 using homogeneous time-resolved fluorescence (TRF) assay. Correlation between oxytosis inhibitory and BACE-1 inhibitory activity of resveratrol derivatives was statistically significant, supporting the notion that BACE-1 may act as pivotal mediator of neuronal cell oxytosis. Four of the biologically evaluated resveratrol analogs demonstrated considerably higher activity than resveratrol in either assay. The discovery of some “hits” led us to initiate detailed docking studies associated with Molecular Dynamics in order to provide a plausible explanation for the experimental results and understand their molecular basis of action