harmine and Malaria--Falciparum

Malaria remains one of the major health problems worldwide. The lack of an effective vaccine and the increasing resistance of Plasmodium to the approved antimalarial drugs demands the development of novel antiplasmodial agents that can effectively prevent and/or treat this disease. Harmiquins represent hybrids that combine two moieties with different mechanisms of antiplasmodial activity in one molecule, i.e., a chloroquine (CQ) scaffold, known to inhibit heme polymerization and a β-carboline ring capable of binding to P. falciparum heat shock protein 90 (PfHsp90). Here we present their synthesis, evaluation of biological activity and potential mechanism of action. The synthesized hybrids differed in the type of linker employed (triazole ring or amide bond) and in the position of the substitution on the β-carboline core of harmine. The antiplasmodial activity of harmiquins was evaluated against the erythrocytic stage of the Plasmodium life cycle, and their cytotoxic effect was tested on HepG2 cells. The results showed that harmiquins exerted remarkable activity against both CQ-sensitive (Pf3D7) and CQ-resistant (PfDd2, PfK1, and Pf7G8). P. falciparum strains. The most active compound, harmiquine 32, displayed single-digit nanomolar IC

Topics: Antimalarials; Chloroquine; Harmine; Heme; Humans; Malaria, Falciparum; Plasmodium falciparum

Cancer and malaria are both global health threats. Due to the increase in the resistance to the known drugs, research on new active substances is a priority. Here, we present the design, synthesis, and evaluation of the biological activity of harmicens, hybrids composed of covalently bound harmine/β-carboline and ferrocene scaffolds. Structural diversity was achieved by varying the type and length of the linker between the β-carboline ring and ferrocene, as well as its position on the β-carboline ring. Triazole-type harmicens were prepared using Cu(I)-catalyzed azide-alkyne cycloaddition, while the synthesis of amide-type harmicens was carried out by applying a standard coupling reaction. The results of in vitro biological assays showed that the harmicens exerted moderate antiplasmodial activity against the erythrocytic stage of P. falciparum (IC50 in submicromolar and low micromolar range) and significant and selective antiproliferative activity against the MCF-7 and HCT116 cell lines (IC50 in the single-digit micromolar range, SI > 5.9). Cell localization experiments showed different localizations of nonselective harmicene 36 and HCT116-selective compound 28, which clearly entered the nucleus. A cell cycle analysis revealed that selective harmicene 28 had already induced G1 cell cycle arrest after 24 h, followed by G2/M arrest with a concomitant drastic reduction in the percentage of cells in the S phase, whereas the effect of nonselective compound 36 on the cell cycle was much less pronounced, which agreed with their different localizations within the cell.

Topics: Antineoplastic Agents; Apoptosis; Carbolines; Cell Line, Tumor; Cell Proliferation; Drug Screening Assays, Antitumor; G2 Phase Cell Cycle Checkpoints; Harmine; Humans; Malaria, Falciparum; Metallocenes; Structure-Activity Relationship

Infection by Plasmodium falciparum is the leading cause of malaria in humans. The parasite contains a unique and essential plastid-like organelle called the apicoplast that, similar to the mitochondria and chloroplast, houses its own genome that must undergo replication and repair. The putative apicoplast replicative DNA polymerase, POM1, has no direct orthologs in mammals, making the P. falciparum POM1 an attractive antimalarial drug target. Here, we report on a fluorescent high-throughput DNA polymerase assay that relies on the ability of POM1 to perform strand-displacement synthesis through the stem of a DNA hairpin substrate, thereby separating a Cy3 dye from a quencher. Assay-validation experiments were performed using 384-well plates and resulted in a signal window of 7.90 and aZ' factor of 0.71. A pilot screen of a 2880-compound library identified 62 possible inhibitors that cause more than 50% inhibition of polymerase activity. The simplicity and statistical robustness of the assay suggest it is well suited for the screening of novel apicoplast polymerase inhibitors that may serve as lead compounds in antimalarial drug-discovery efforts.

Topics: Antimalarials; Apicoplasts; Chloroplasts; DNA; DNA-Directed DNA Polymerase; Drug Discovery; Exonucleases; Humans; Kinetics; Malaria, Falciparum; Mitochondria; Multienzyme Complexes; Nucleic Acid Synthesis Inhibitors; Peptide Library; Plasmodium falciparum; Protozoan Proteins; Spectrometry, Fluorescence