Novel matrix metalloproteinase inhibitors derived from quinoxalinone scaffold (Part I)

Rational Design of Long-Circulating Bright Fluorescent Probe for In Vivo Imaging of Amyloid-β Plaques in Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the pathological accumulation of amyloid-β (Aβ) plaques, which serve as crucial biomarkers for disease diagnosis and therapeutic evaluation. While fluorescence imaging has emerged as a powerful technique for Aβ detection, current probes face limitations in clinical application due to insufficient photostability and short blood half-life, resulting in compromised signal-to-noise ratios (SNRs) and imaging resolution. Herein, two bright quinoxalinone-based fluorescent probes (QNO-AD-PEGs) were presented, which incorporate hydrophilic poly(ethylene glycol) (PEG) chains for enhanced biocompatibility and an Aβ-specific N,N-dimethylaminophenyl recognition unit. QNO-AD-PEG1 demonstrated exceptional binding affinity for Aβ42 aggregates (Kd = 42 nM) and a remarkable 49-fold fluorescence enhancement upon target engagement, with a quantum yield (ΦAβ) of 11.45%. In vivo imaging revealed that QNO-AD-PEG1 effectively crossed the blood-brain barrier (BBB) and exhibited a prolonged half-life (315 min). Notably, the probe successfully visualized age-dependent Aβ plaque progression in AD mouse models. This study presents a significant breakthrough in molecular imaging for neurodegenerative diseases, offering a versatile tool for both fundamental AD research and potential clinical applications.

Rational Design of Quinoxalinone-Based Red-Emitting Probes for High-Affinity and Long-Term Visualizing Amyloid-β In Vivo

Alzheimer's disease (AD) is a progressive neurodegenerative disease with insidious onset, and the deposition of amyloid-β (Aβ) is believed to be one of the main cause. Fluorescence imaging is a promising technique for this task, but the Aβ gold standard probe ThT developed based on this still has shortcomings. The development of a new fluorescent probe to detect Aβ plaques is thought to be essential. Herein, a series of red to near-infrared emitting fluorescent probes QNO-ADs with newly quinoxalinone skeleton are designed to detect Aβ plaques. They all demonstrate excellent optical properties and high binding affinity (∼K_d = 20 nM) to Aβ aggregates. As the most outstanding candidate, QNO-AD-3 shows significant signal-to-noise (S/N) ratio at the level of in vitro binding studies, and the brilliant fluorescence staining results in favor of grasping the approximate distribution of Aβ plaques in the brain slice. In vivo Aβ plaques imaging suggests that QNO-AD-3 can cross the BBB and have a long retention time in the brain with low biological toxicity. In addition, the results of docking theoretical calculation also provide some references for the design of Aβ probe. Overall, given the high affinity of QNO-AD-3 and the ability to monitor Aβ plaques for a long time that is not common now, we believe QNO-AD-3 will be an effective tool for an Aβ-related matrix and AD disease research in the future.

Functionalized quinoxalinones as privileged structures with broad-ranging pharmacological activities

Quinoxalinones are a class of heterocyclic compounds which attract extensive attention owing to their potential in the field of organic synthesis and medicinal chemistry. During the past few decades, many new synthetic strategies toward the functionalization of quinoxalinone based scaffolds have been witnessed. Regrettably, there are only a few reports on the pharmacological activities of quinoxalinone scaffolds from a medicinal chemistry perspective. Therefore, herein we intend to outline the applications of multifunctional quinoxalinones as privileged structures possessing various biological activities, including anticancer, neuroprotective, antibacterial, antiviral, antiparasitic, anti-inflammatory, antiallergic, anti-cardiovascular, anti-diabetes, antioxidation, etc. We hope that this review will facilitate the development of quinoxalinone derivatives in medicinal chemistry.

Design, synthesis, and biological evaluation of 4-phenoxybenzenesulfonyl pyrrolidine derivatives as matrix metalloproteinase inhibitors

A series of 4-phenoxybenzenesulfonyl pyrrolidine derivatives were designed, synthesized, and evaluated as matrix metalloproteinases (MMPs) inhibitors. All of the synthesized compounds displayed inhibitory activity against MMP-2 and MMP-9. Compounds 4a, 4e, and 4i displayed more potent activity than the other compounds. While the three compounds mildly or moderately inhibited the proliferation of cancer cells, they significantly suppressed the migration and invasion of cancer cells at relatively low concentrations as determined by a wound healing assay and transwell assay. In addition, compound 4e suppressed vascular endothelial cell tube formation and sprouting of microvessels from aortic rings in vitro in a dose-dependent manner. Compound 4e markedly suppressed the pulmonary metastasis of H22 cells in mice. These findings along with molecular docking results suggested that compound 4e might be a promising candidate for further structural optimization to develop MMP inhibitors as potential anticancer agents.

Synthetic routes and structure-activity relationships (SAR) of anti-HIV agents: A key review

The worldwide increase of AIDS, an epidemic infection in constant development has an essential and still requires potent antiretroviral chemotherapeutic agents for reducing the integer of deaths caused by HIV. Thus, there is an urgent need for new anti-HIV drug candidates with increased strength, new targets, superior pharmacokinetic properties, and compact side effects. From this viewpoint, we first review present strategies of anti-HIV drug innovation and the synthesis of heterocyclic or natural compound as anti-HIV agents for facilitating the development of more influential and successful anti-HIV agents.

Reaction-Based Color-Convertible Fluorescent Probe for Ferroptosis Identification

Ferroptosis is an iron-mediated, caspase-independent pathway of cell death that is accompanied with the accumulations of reactive oxygen species (ROS) and oxygenases, as well as being involved in many other pathophysiological procedures. However, specific and rapid monitoring of ferroptosis in living cells or tissues has not been achieved so far. Herein, a quinoxalinone-based fluorescent probe (termed as Quinos-4, or QS-4) with a reactive aromatic thioether moiety was designed for ferroptosis identification. Upon exposing it to high levels of ROS and hemeoxygenase-1 (HO-1), which are considered as the biochemical characteristics of ferroptosis, QS-4 could be oxidized into a sulfoxide derivative (QSO-4) and its original aggregation-induced enhanced red fluorescence emission could be converted to green fluorescence emission sharply. On the basis of this unique reaction-induced color conversion, this molecular probe can be employed for identifying the occurrence of ferroptosis both in vitro and in vivo.

Recent opportunities in matrix metalloproteinase inhibitor drug design for cancer

INTRODUCTION

The overexpression of matrix metalloproteinase (MMP) plays an important role in the context of tumor invasion and metastasis, and MMP-2 has been characterized as the most validated target for cancer. Therefore, it is necessary to design matrix metalloproteinase inhibitors (MMPIs) that would be active and selective against MMP-2 but non-selective toward other MMPs. Areas covered: This article clearly describes the structural character of MMP-2 followed by a review of the recent development of selective MMP-2 inhibitors based on their basic structures. Expert opinion: Over the past 30 years, MMPs have been considered to be attractive cancer targets, and several different types of synthetic inhibitors have been identified as anticancer agents, but only a small number of small MMPIs have been examined in clinical trials, and none of these molecules has been established as anticancer drugs due to their adverse effects. One major possibility is that the MMPIs used in clinical trials were broad-spectrum drugs that also inhibited the anti-tumor effects and influenced the mediation of the normal physiological processes of MMPs. MMP-2 has recently been characterized as the most validated target for cancer. Therefore, the design and synthesis of selective MMP-2 inhibitors would be helpful for the treatment of cancer.

Spectral and kinetic properties of radicals derived from oxidation of quinoxalin-2-one and its methyl derivative

The kinetics and spectral characteristics of the transients formed in the reactions of •OH and •N3 with quinoxalin-2(1H)-one (Q), its methyl derivative, 3-methylquinoxalin-2(1H)-one (3-MeQ) and pyrazin-2-one (Pyr) were studied by pulse radiolysis in aqueous solutions at pH 7. The transient absorption spectra recorded in the reactions of •OH with Q and 3-MeQ consisted of an absorption band with λmax = 470 nm assigned to the OH-adducts on the benzene ring, and a second band with λmax = 390 nm (for Q) and 370 nm (for 3-MeQ) assigned, inter alia, to the N-centered radicals on a pyrazin-2-one ring. The rate constants of the reactions of •OH with Q and 3-MeQ were found to be in the interval (5.9-9.7) × 109 M-1·s-1 and were assigned to their addition to benzene and pyrazin-2-one rings and H-abstraction from the pyrazin-2-one nitrogen. In turn, the transient absorption spectrum observed in the reaction of •N3 exhibits an absorption band with λmax = 350 nm. This absorption was assigned to the N-centered radical on the Pyr ring formed after deprotonation of the respective radical cation resulting from one-electron oxidation of 3-MeQ. The rate constant of the reaction of •N3 with 3 MeQ was found to be (6.0 ± 0.5) × 109 M-1·s-1. Oxidation of 3-MeQ by •N3 and Pyr by •OH and •N3 confirms earlier spectral assignments. With the rate constant of the •OH radical with Pyr (k = 9.2 ± 0.2) × 109 M-1·s‒1, a primary distribution of the •OH attack was estimated nearly equal between benzene and pyrazin-2-one rings.

Exploring QSAR and pharmacophore mapping of structurally diverse selective matrix metalloproteinase-2 inhibitors

Objectives and Methods

Matrix metalloproteinase-2 (MMP-2) is a potential target in metastases. Regression (conventional 2D QSAR) and classification (recursive partitioning (RP), Bayesian modelling) QSAR, pharmacophore mapping and 3D QSAR (comparative molecular field analysis and comparative molecular similarity analysis) were performed on 202 MMP-2 inhibitors.

Key findings

Quality of the regression models was justified by internal (Q2) and external (R2Pred) cross-validation parameters. Stepwise regression was used to develop linear model (Q2 = 0.822, R2Pred = 0.667). Genetic algorithm developed linear (Q2 = 0.845, R2Pred = 0.638) and spline model (Q2  = 0.882, R2Pred = 0.644). The RP and Bayesian models showed cross-validated area under receiver operating characteristic curve (AUCROC_CV) of 0.805 and 0.979 respectively. QSAR models depicted importance of descriptors like five-membered rings, fractional positively charged surface area, lipophilocity and so on. Higher molecular volume was found to be detrimental. Pharmacophore mapping was performed with two tools – Hypogen and PHASE. Both models indicated that one hydrophobic and three hydrogen bond acceptor features are essential. The Pharmacophore-aligned structures were used for CoMFA (Q2 of 0.586 and R2Pred of 0.689) and CoMSIA (Q2 of 0.673 and R2Pred of 0.758), results of which complied with the other analyses.

Conclusions

All modelling techniques were compared to each other. The current study may help in designing novel MMP-2 inhibitors.

Concise route to a series of novel 3-(tetrazol-5-yl)quinoxalin-2(1H)-ones

This report presents a novel three step solution phase protocol to synthesize 3-(tetrazol-5-yl)quinoxalin-2(1H)-ones. The strategy utilizes ethyl glyoxalate and mono-N-Boc-protected-o-phenylenediamine derivatives in the Ugi-Azide multi-component reaction (MCR) to generate a unique 1,5-disubstituted tetrazole. Subsequent acid treatment stimulates a simultaneous Boc deprotection and intramolecular cyclization leading to bis-3,4-dihydroquinoxalinone tetrazoles. Direct oxidation using a stable solid-phase radical catalyst (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) with ceric ammonium nitrate (CAN) in catalytic fashion initiating aerobic oxidation, completes the entire procedure to generate a series of original unique bis-quinoxalinone tetrazoles. The method was also expanded to produce a bis-benzodiazepine tetrazole.