Synthesis, mechanistic and synergy studies of diarylidenecyclohexanone derivatives as new antiplasmodial pharmacophores

Diarylidene-N-Methyl-4-Piperidones and Spirobibenzopyrans as Antioxidant and Anti-Inflammatory Agents

Curcumin has antioxidant properties resulting from its radical scavenging ability and inhibition of inflammation-associated factors. However, its lack of solubility, instability, and poor bioavailability are impediments to its therapeutic use. As potential alternatives, we synthesized and performed chemical analysis of thirty diarylidene-N-methyl-4-piperidone (DANMP), diheteroarylidene-N-methyl-4-piperidone (DHANMP), and spirobibenzopyran (SBP) derivatives, one of which was also characterized by single crystal X-ray diffraction. All compounds were evaluated for antioxidant activity via 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay and for drug-like properties in silico. A subset of five compounds was investigated in terms of aqueous solubilities, which were significantly improved compared to that of curcumin. In vitro assessments of cellular and anti-inflammatory effects were conducted via real time polymerase chain reaction (RT-PCR) and Griess assays to evaluate the presence of inflammatory/activated (M1) markers and production of nitric oxide (NO) species, which are associated with inflammation. The five compounds reduced levels of markers and NO to extents similar to or better than curcumin in inflamed cells, and showed no adverse effects on cell viability. We show that these compounds possess anti-inflammatory properties and may be used as curcumin-substitutes with improved characteristics.

Structure-activity relationship of dibenzylideneacetone analogs against the neglected disease pathogen, Trypanosoma brucei

Trypanosoma brucei is a protozoan parasite that causes Human African Trypanosomiasis (HAT), a neglected tropical disease (NTD) that is endemic in 36 countries in sub-Saharan Africa. Only a handful drugs are available for treatment, and these have limitations, including toxicity and drug resistance. Using the natural product, curcumin, as a starting point, several curcuminoids and related analogs were evaluated against bloodstream forms of T. b. brucei. A particular subset of dibenzylideneacetone (DBA) compounds exhibited potent in vitro antitrypanosomal activity with sub-micromolar EC₅₀ values. A structure-activity relationship study including 26 DBA analogs was initiated, and several compounds exhibited EC₅₀ values as low as 200 nM. Cytotoxicity counter screens in HEK293 cells identified several compounds having selectivity indices above 10. These data suggest that DBAs offer starting points for a new small molecule therapy of HAT.

Antiplasmodial and Antimalarial Activity of 3,5-Diarylidenetetrahydro-2H-pyran-4(3H)-ones via Inhibition of Plasmodium falciparum Pyridoxal Synthase

A series of 22 different 3,5-diarylidenetetrahydro-2H-pyran-4(3H)-ones (DATPs) were synthesized, characterized, and screened for their in vitro antiplasmodial activities against chloroquine (CQ)-sensitive Pf3D7, CQ-resistant PfINDO, and artemisinin-resistant PfMRA-1240 strains of Plasmodium falciparum. DATP 19 (3,5-bis(4-hydroxy-3,5-dimethoxybenzylidene)tetrahydro-2H-pyran-4(3H)-one) was found to be the most potent (IC₅₀ 1.07 μM) against PfMRA-1240, whereas 21 (3,5-bis(3,4,5-trimethoxybenzylidene)tetrahydro-2H-pyran-4(3H)-one) showed IC₅₀ values of 1.72 and 1.44 μM against Pf3D7 and PfINDO, respectively. Resistance indices (RI) as low as 0.2 to 0.5 for 10 (3,5-bis(4-nitrobenzylidene)tetrahydro-2H-pyran-4(3H)-one) and 20 (3,5-bis(3-nitrobenzylidene)tetrahydro-2H-pyran-4(3H)-one), and <1 for most other DATPs reveals their greater potency against resistant strains than the sensitive one. The single-crystal XRD data for DATP 21 are reported. In silico support was obtained through docking studies. Killing all three strains within 4-8 h, these DATPs showed rapid kill kinetics toward the trophozoite stage. Furthermore, DATP 18 (3,5-bis(quinolin-4-ylmethylene)tetrahydro-2H-pyran-4(3H)-one) inhibited PfPdx1 enzyme activity with IC₅₀ 20.34 μM, which is about twofold lower than that (IC₅₀ 43 μM) for an already known inhibitor 4PEHz. At an oral dose of 300 mg/kg body weight, DATPs 19 and 21 were found to be nontoxic to mice, and at 100 mg/kg body weight, DATP 19 was found to suppress parasitaemia, which led to an increase in median survival time by three days relative to untreated control mice in a malaria curative study.

Synthesis, in vitro anti-plasmodial potency, in-silico-cum-SPR binding with inhibition of PfPyridoxal synthase and rapid parasiticidal action by 3,5-bis{(E) arylidene}-N-methyl-4-piperidones

DANMPs have been identified as new pharmacophores that have the ability to target PfPyridoxal synthase and cause rapid killing of the malaria parasite.