Synthetic compounds from an in house library as inhibitors of falcipain-2 from Plasmodium falciparum

Abstract

Falcipain-2 (FP-2) is a key cysteine protease from the malaria parasite Plasmodium falciparum. Many previous studies have identified FP-2 inhibitors; however, none has yet met the criteria for an antimalarial drug candidate. In this work, we assayed an in-house library of non-peptidic organic compounds, including (E)-chalcones, (E)-N’-benzylidene-benzohydrazides and alkyl-esters of gallic acid, and assessed the activity toward FP-2 and their mechanisms of inhibition. The (E)-chalcones 48, 54 and 66 showed the lowest IC₅₀ values (8.5 ± 0.8 µM, 9.5 ± 0.2 µM and 4.9 ± 1.3 µM, respectively). The best inhibitor (compound 66) demonstrated non-competitive inhibition, and using mass spectrometry and fluorescence spectroscopy assays, we suggest a potential allosteric site for the interaction of this compound, located between the catalytic site and the hemoglobin binding arm in FP-2. We combined structural biology tools and mass spectrometry to characterize the inhibition mechanisms of novel compounds targeting FP-2.

• Chalcones
• falcipain-2 inhibitors
• malaria
• Plasmodium falciparum

Acknowledgements

We thank Taisa Regina Stumpf for technical support in some of the chemical synthesis.

Declaration of interest

We thank CNPq and CAPES for financial support.

Supplementary material available online

Supplementary Table 1 and Figures S1–S4.