Synthesis and antikinetoplastid activities of 3-substituted quinolinones derivatives

Discovery of Quinolinone Hybrids as Dual Inhibitors of Acetylcholinesterase and Aβ Aggregation for Alzheimer's Disease Therapy

The development of multitargeted therapeutics has evolved as a promising strategy to identify efficient therapeutics for neurological disorders. We report herein new quinolinone hybrids as dual inhibitors of acetylcholinesterase (AChE) and Aβ aggregation that function as multitargeted ligands for Alzheimer's disease. The quinoline hybrids (AM1-AM16) were screened for their ability to inhibit AChE, BACE1, amyloid fibrillation, α-syn aggregation, and tau aggregation. Among the tested compounds, AM5 and AM10 inhibited AChE activity by more than 80% at single-dose screening and possessed a remarkable ability to inhibit the fibrillation of Aβ42 oligomers at 10 μM. In addition, dose-dependent screening of AM5 and AM10 was performed, giving half-maximal AChE inhibitory concentration (IC50) values of 1.29 ± 0.13 and 1.72 ± 0.18 μM, respectively. In addition, AM5 and AM10 demonstrated concentration-dependent inhibitory profiles for the aggregation of Aβ42 oligomers with estimated IC50 values of 4.93 ± 0.8 and 1.42 ± 0.3 μM, respectively. Moreover, the neuroprotective properties of the lead compounds AM5 and AM10 were determined in SH-SY5Y cells incubated with Aβ oligomers. This work would enable future research efforts aiming at the structural optimization of AM5 and AM10 to develop potent dual inhibitors of AChE and amyloid aggregation. Furthermore, the in vivo assay confirmed the antioxidant activity of compounds AM5 and AM10 through increasing GSH, CAT, and SOD activities that are responsible for scavenging the ROS and restoring its normal level. Blood investigation illustrated the protective activity of the two compounds against lead-induced neurotoxicity through retaining hematological and liver enzymes near normal levels. Finally, immunohistochemistry investigation revealed the inhibitory activity of β-amyloid (Aβ) aggregation.

Vibronic spectra of jet-cooled 1-methyl-2(1H)-quinolinone studied by Fluorescence spectroscopy and Quantum chemical calculation

1-methyl-2(1H)-quinolinone (MeQone) forms the framework of several hundred quinolone alkaloid molecules, both natural and synthetic, which are being used in various biological applications. In this work, we present experimental and theoretical spectroscopic investigation on the MeQone in its ground and first electronic excited states. The vibronically resolved fluorescence excitation (FE) spectrum of MeQone is recorded within 700 cm^-1 to the electronic origin under the supersonic jet-cooled condition. The dispersed fluorescence (DF) spectra for bands observed in the FE spectrum were also recorded. Bands observed in DF spectra were identified and assigned with the help of Density Functional Theory (DFT) calculated harmonic vibrational frequencies. Based on the assignments of bands in the ground electronic state and TD-DFT calculated frequencies for the first excited state, we have identified and successfully assigned the bands observed in FE spectrum. This study could be helpful to understand the photophysical properties of MeQone derivatives, the quinolone alkaloids.

Key role of the macrophage microtubule network in the intracellular lifestyle of Leishmania amazonensis

We conducted a study to decipher the mechanism of the formation of the large communal Leishmania amazonensis-containing parasitophorous vacuole (PV) and found that the macrophage microtubule (MT) network dynamically orchestrates the intracellular lifestyle of this intracellular parasite. Physical disassembly of the MT network of macrophage-like RAW 264.7 cells or silencing of the dynein gene, encoding the MT-associated molecular motor that powers MT-dependent vacuolar movement, by siRNA resulted in most of the infected cells hosting only tight parasite-containing phagosome-like vacuoles randomly distributed throughout the cytoplasm, each insulating a single parasite. Only a minority of the infected cells hosted both isolated parasite-containing phagosome-like vacuoles and a small communal PV, insulating a maximum of two to three parasites. The tight parasite-containing phagosome-like vacuoles never matured, whereas the small PVs only matured to a small degree, shown by the absence or faint acquisition of host-cell endolysosomal characteristics. As a consequence, the parasites were unable to successfully complete promastigote-to-amastigote differentiation and died, regardless of the type of insulation.

Ab initio and NBO studies of methyl internal rotation in 1-methyl-2(1H)-quinolinone: effect of aromatic substitution to 1-methyl-2(1H)-pyridone

1-methyl-2(1H)-quinolinone (MeQone) forms the framework of several hundred alkaloid molecules both natural and synthetic being used for various biological applications. From chemical structure point of view, the molecules can also be seen as an aromatic ring fused to 1-methyl-2(1H)-pyridone (1-MPY). In this work, we present theoretical investigations on internal rotation of methyl group in MeQone in light of 1-MPY. We looked into the change in the three-fold (V₃) methyl internal rotation barrier resulted from the aromatic ring substitution to 1-MPY. The V₃ term in two molecules were calculated using density functional theory and Hartree-Fock theory with different basis sets. MeQone has calculated V₃ term (in S₀ state) three times higher in magnitude compared with that of 1-MPY. The role of aromatic substitution in increase of V₃ term is investigated using natural bond orbital (NBO) analyses. In the NBO analysis, it is found that the aromatic ring as highly delocalized π-system lowers the magnitude of hyperconjugation energy in MeQone compared with 1-MPY. This is due to the extension of delocalization of π-electrons to pyridone ring which lowers the orbital overlap. However, the Lewis energy increases substantially and make the overall barrier energy higher in MeQone compared with 1-MPY. From our study, we conclude that in the molecules such as 1-MPY and MeQone where the methyl group has two single bonds vicinal to it, the overall hyperconjugation energy is always barrier forming with nonlocal interactions playing significant role. Also, the Lewis energy plays the decisive role in barrier formation, and its magnitude can be tuned by tuning the π-electron delocalization. We have also looked into the change in methyl group conformation upon electronic excitation to S₁ state. In 1-MPY, the methyl group rotated by 60° upon excitation whereas in MeQone, there was no conformational change. Strong π*-σ* interaction in LUMO in top-of-barrier conformation is responsible for the change in the methyl group conformation in 1-MPY, whereas same π*-σ* interaction in LUMO of minimum energy conformation results in unchanged excited state conformation in MeQone. Graphical abstract.

Aryldiazoquinoline based multifunctional small molecules for modulating Aβ42aggregation and cholinesterase activity related to Alzheimer's disease

Novel series of aryldiazoquinoline multifunctional molecules controls amyloid formation and neuro-protective role by inhibiting esterase enzymes.

Design, synthesis and evaluation of quinolinone derivatives containing dithiocarbamate moiety as multifunctional AChE inhibitors for the treatment of Alzheimer's disease

A series of novel quinolinone derivatives bearing dithiocarbamate moiety were designed and synthesised as multifunctional AChE inhibitors for the treatment of AD. Most of these compounds exhibited strong and clearly selective inhibition to eeAChE. Among them, compound 4c was identified as the most potent inhibitor to both eeAChE and hAChE (IC₅₀ = 0.22 μM for eeAChE; IC₅₀ = 0.16 μM for hAChE), and it was also the best inhibitor to AChE-induced Aβ aggregation (29.02% at 100 μM) and an efficient inhibitor to self-induced Aβ aggregation (30.67% at 25 μM). Kinetic and molecular modelling studies indicated that compound 4c was a mixed-type inhibitor, which could interact simultaneously with the catalytic anionic site (CAS) and the peripheral anionic site (PAS) of AChE. In addition, 4c had good ability to cross the BBB, showed no toxicity on SH-SY5Y neuroblastoma cells and was well tolerated in mice at doses up to 2500 mg/kg (po).

A palladium-catalyzed intramolecular carbonylative annulation reaction for the synthesis of 4,5-fused tricyclic 2-quinolones

A new method for the synthesis of 4,5-fused tricyclic 2-quinolones via a palladium-catalyzed intramolecular carbonylative annulation reaction is described.

"Squalenoylcurcumin" nanoassemblies as water-dispersible drug candidates with antileishmanial activity

Curcumin, a natural polyphenolic compound, showed antiparasitic potential, including trypanocidal and leishmanicidal activity, in several in vitro and in vivo models. The molecule is well tolerated in humans. However, it is insoluble in water and displays poor oral bioavailability as a result of low absorption. New derivatives of curcumin were prepared by esterification of one or two of its phenolic groups with 1,1',2-tris-norsqualenic acid. These "squalenoylcurcumins" were formulated as water-dispersible nanoassemblies of homogeneous size, and they proved to be stable. Squalenoylcurcumins were inactive against Trypanosoma brucei brucei trypomastigotes, even as nanoassemblies, in contrast with curcumin. However, against Leishmania donovani promastigotes, the activities of the squalenoylcurcumins and their nanoassemblies were enhanced relative to that of curcumin. In L. donovani axenic and intramacrophagic amastigotes, they showed activity in the range of miltefosine, with good selectivity indexes. In regard to their dispersibility in water and to the safety of curcumin, these nanoassemblies are promising candidates for preclinical study toward the treatment of visceral leishmaniasis.

Design, synthesis and in vitro antikinetoplastid evaluation of N-acylated putrescine, spermidine and spermine derivatives

A structure-activity relationship study on polyamine derivatives led to the synthesis and the determination of antikinetoplastid activity of 17 compounds. Among them, a spermidine derivative (compound 13) was specifically active in vitro against Leishmania donovani axenic amastigotes (IC50 at 5.4μM; Selectivity Index >18.5) and a spermine derivative (compound 28) specifically active against Trypanosoma brucei gambiense (IC50 at 1.9μM; Selectivity Index >52).

Novel hybrid selenosulfonamides as potent antileishmanial agents

Diselenide and sulfonamide derivatives have recently attracted considerable interest as leishmanicidal agents in drug discovery. In this study, a novel series of sixteen hybrid selenosulfonamides has been synthesized and screened for their in vitro activity against Leishmania infantum intracellular amastigotes and THP-1 cells. These assays revealed that most of the compounds exhibited antileishmanial activity in the low micromolar range and led us to identify three lead compounds (derivatives 2, 7 and 14) with IC50 values ranging from 0.83 to 1.47 μM and selectivity indexes (SI) over 17, much higher than those observed for the reference drugs miltefosine and edelfosine. When evaluated against intracellular amastigotes, hybrid compound 7 emerged as the most active compound (IC50 = 2.8 μM), showing higher activity and much less toxicity against THP-1 cells than edelfosine. These compounds could potentially serve as templates for future drug-optimization and drug-development efforts for their use as therapeutic agents in developing countries.

Synthesis and anti-parasitic activity of a novel quinolinone-chalcone series

A series of novel quinolinone-chalcone hybrids and analogues were designed, synthesized and their biological activity against the mammalian stages of Trypanosoma brucei and Leishmania infantum evaluated. Promising molecular scaffolds with significant microbicidal activity and low cytotoxicity were identified. Quinolinone-chalcone 10 exhibited anti-parasitic properties against both organisms, being the most potent anti-L. infantum agent of the entire series (IC50 value of 1.3±0.1 μM). Compounds 4 and 11 showed potency toward the intracellular, amastigote stage of L. infantum (IC50 values of 2.1±0.6 and 3.1±1.05 μM, respectively). Promising trypanocidal compounds include 5 and 10 (IC50 values of 2.6±0.1 and 3.3±0.1 μM, respectively) as well as 6 and 9 (both having IC50 values of <5 μM). Chemical modifications on the quinolinone-chalcone scaffold were performed on selected compounds in order to investigate the influence of these structural features on antiparasitic activity.

11-(4-Methyl-phen-yl)-8,9-dihydro-7H-benzo[f]cyclo-penta-[b]quinolin-10(11H)-one

In the title compound, C₂₃H₁₉NO, the naphthalene ring system and the cyclo­pent-2-enone ring exhibit planar conformations with maximum deviations of 0.034 (1) and 0.02 (1) Å, respectively. The 1,4-dihydro­pyridine ring adopts an envelope conformation with the C atom bearing the p-tolyl ring as the flap atom. Inter­molecular N—H⋯O hydrogen bonds and C—H⋯π inter­actions stabilize the crystal packing.