2’-Hydroxy-4’,5’-dimethyl-4-dimethylaminochalcone, a novel fluorescent flavonoid with capacity to detect aluminium in cells and modulate Alzheimer’s disease targets

Fluorescence of 2-Hydroxy Chalcone Analogs with Extended Conjugation: ESIPT vs. ICT Pathways

The chalcone derivatives with hydroxy group (2) have been examined using low-temperature fluorescence spectroscopy. The study aimed to freeze the intramolecular charge transfer (ICT) motion in order to reveal the potential hidden transition(s) that are difficult to observe at room temperature. Although chalcone 2 revealed one emission peak at ~667 nm at room temperature, it exhibited two emission peaks (λem = 580 and 636 nm) in EtOH at liquid N2 temperatures (77 K). With the aid of model compound 3 with methoxy group and aluminum complex 2-Al3+, attempts were made to assign these emission peaks. The results point towards the possibility of the coexistence of ICT and excited state intramolecular proton transfer (ESIPT) in the chalcone derivatives with extended conjugation.

An ultra-sensitive fluorescent probe for recognition of aluminum ions and its application in environment, food, and living organisms

The concentration of aluminum ions (Al3+) is closely related to the ecological environment, food safety, and human health, with excessive accumulation of Al3+ causing irreversible damage to both the ecological balance and human health. Therefore, a fluorescent probe ABHS, based on aminobenzoylhydrazide Schiff-base, was designed and synthesized in one step with a high yield. ABHS can form a 1:1 coordination complex with Al3+ in a pure water system. It exhibits ultra-sensitive and accurate detection of Al3+ even at low concentration of Al3+, with the detection limit of 6.7 nM. Furthermore, ABHS demonstrated significant enhancement of specific fluorescence for Al3+, with rapid response speed, good stability, and robust resistance to interference. Importantly, ABHS has shown excellent detection and imaging capabilities even in complex real environmental samples, food samples, and living organisms.

A coumarin-based multifunctional chemosensor for Cu2+/Al3+ as an AD theranostic agent: Synthesis, X-ray single crystal analysis and activity study

The pathogenesis of Alzheimer's disease (AD) is complex. So far there is no effective drug to treat the disease. The pathological changes of AD began 30 years before symptoms, so early diagnosis is considered to be important for AD treatment. Integrating diagnosis and therapy into a single regent has provided a new opportunity for AD treatment. Given that metal dyshomeostasis is thought to be one of the key factors to cause AD, a Schiff base substituted coumarin (probe 1) has been designed and synthesized as a selective metal chelator for multi-factor anti-AD in this work. The results of metal ions recognition showed that probe 1 had high selective fluorescent turn-on response to Al3+ and fluorescent turn-off response to Cu2+, due to intramolecular charge transfer (ICT) mechanism. Meanwhile, the results of both in vitro and in vivo bioactivities evaluation including metal chelation, reactive oxide species (ROS) elimination, self-/Cu2+-induced Aβ aggregation showed that 1 and 1-Cu(II) complex had excellent synergistic anti-AD activities. In addition, 1 had low cytotoxicity and was predicted to cross the blood-brain barrier (BBB). Noticeably, X-ray single crystal diffraction of 1-Cu(II) provided molecular level information to explain the structure and theranostic activity relationship. To sum up, 1 may be a promising candidate for the development of AD theranostic agent.

A julolidine-chalcone-based fluorescent probe for detection of Al3+ in real water sample and cell imaging

A fluorescent probe 1 based on julolidine-chalcone derivative, which can specifically recognize aluminum ion with high selectivity and anti-interference, was developed. Probe 1 has good fluorescence stability and can detect Al³⁺ with turn-on fluorescence in a wide pH range of 4.0-9.0. The probe has good repeatability for the detection of Al³⁺ and fluorescence turn-on and off can be repeated with the alternate Al³⁺ and EDTA. The sensing mechanism is speculated that Al³⁺ will coordinate with hydroxyl oxygen and carbonyl oxygen on the probe through in situ ¹H NMR and HRMS combing with Job's plot. The probe can also detect Al³⁺ in actual water samples and applied to monitor Al³⁺ in biological system.

A multifunctional metal regulator as the potential theranostic agent: Design, synthesis, anti-AD activities and metallic ion sensing properties

Although there is no cure for Alzheimer's disease (AD) due to its complex pathogenesis, early detection and treatment can help delay the development of the disease. So, it is necessary to develop multifunctional metal regulators that can integrate the therapeutics and diagnostics effect against AD. In this work, N-(anthracene-9-ylmethylene)benzohydrazide (probe 1), a fluorescent probe with imine and carbonyl as chelating sites was designed and synthesized. Results showed that 1 had good activities related to AD, such as regulation of metal homeostasis, inhibition of β-amyloid (Aβ) aggregation and scavenging of reactive oxygen species. The selectivity experiment showed that probe 1 had a good recognition effect on Cu²⁺. Fluorescence imaging assay also indicated that probe 1 had a good fluorescence imaging effect on Cu²⁺ in living cells. Furthermore, probe 1 had showed no cytotoxicity and good BBB permeability. These results indicated that probe 1 had potential diagnostic and therapeutic capabilities, and can be used as the multifunctional theranostic agent for AD.

Complexation of 1,3-dihetaryl-5-phenyl-2-pyrazoline Derivatives with Polyvalent Metal Ions: Quantum Chemical Modeling and Experimental Investigation

1,3,5-Triaryl-2-pyrazoline derivatives with a pyridine ring in position 1 and 2-benzimidazolyl or 2-benzothiazolyl bicycles in position 3 were synthesized. Spectral properties in solvents of similar polarity, i.e. aprotic acetonitrile and in protic methanol, were studied, complexation with cadmium and mercury ions in acetonitrile was elucidated as well. Quantum-chemical modeling with application of the elements of Bader's atoms-in-molecules (AIM) theory of the title molecules conformational structure and 1:1 stoichiometry complexes formed with polyvalent metals of various nature (Mg, Zn, Cd, Pb, Hg, Ba) was conducted. The principal possibility of “nitrogen-sulfur” switching of the metal ions binding sites for the benzothiazole derivative was revealed, and makes possible to classify this compound as “smart ligand”.

Multitarget 2'-hydroxychalcones as potential drugs for the treatment of neurodegenerative disorders and their comorbidities

The complex nature of neurodegenerative diseases (NDDs), such as Alzheimer's disease (AD) and Parkinson's disease (PD) calls for multidirectional treatment. Restoring neurotransmitter levels by combined inhibition of cholinesterases (ChEs) and monoamine oxidases (MAOs, MAO-A and MAO-B), in conjunction with strategies to counteract amyloid β (Aβ) aggregation, may constitute a therapeutically strong multi-target approach for the treatment of NDDs. Chalcones are a subgroup of flavonoids with a broad spectrum of biological activity. We report here the synthesis of 2'-hydroxychalcones as MAO-A and MAO-B inhibitors. Compounds 5c (IC50 = 0.031 ± 0.001 μM), 5a (IC50 = 0.084 ± 0.003 μM), 2c (IC50 = 0.095 ± 0.019 μM) and 2a (IC50 = 0.111 ± 0.006 μM) were the most potent, selective and reversible inhibitors of human (h)MAO-B isoform. hMAO-B inhibitors 1a, 2a and 5a also inhibited murine MAO-B in vivo in mouse brain homogenates. Molecular modelling rationalised the binding mode of 2'-hydroxychalcones in the active site of hMAO-B. Additionally, several derivatives inhibited murine acetylcholinesterase (mAChE) (IC50 values from 4.37 ± 0.83 μM to 15.17 ± 6.03 μM) and reduced the aggregation propensity of Aβ. Moreover, some derivatives bound to the benzodiazepine binding site (BDZ-bs) of the γ-aminobutyric acid A (GABAA) receptors (1a and 2a with Ki = 4.9 ± 1.1 μM and 5.0 ± 1.1 μM, respectively), and exerted sedative and/or anxiolytic like effects on mice. The biological results reported here on 2'-hydroxychalcones provide an extension to previous studies on chalcone scaffold and show them as a potential treatment strategy for NDDs and their associated comorbidities.

A novel dehydroabietic acid-based turn-on fluorescent probe for the detection of bisulfite and its application in live-cell and zebrafish imaging

A novel “Turn-on” fluorescent probe, which displayed prominent sensitivity and selectivity for the detection of HSO3−, was synthesized from dehydroabietic acid. The probe also showed high lysosome-targeting properties when sensing HSO3− in MCF-7 cells.