An ICT-based highly fluorescent isoquinoline scaffold for selective Hg(II) detection in real-water samples: Development of a smart, low-cost RGB-Arduino electronic platform

Selective detection and quantification of Hg2+ ions is crucial to minimize health and environmental risks. Fluorescent organic small-molecule probes have been expeditiously utilized owing to their unique set of improved properties. However, isoquinoline core has not been extensively explored as a fluorescence platform partly due to synthetic challenges. Herein, a serendipitously discovered synthetic route to access a small yet highly functionalized novel isoquinoline-based probe, IQ is reported. The synthesis is achieved through the in-situ generation of ammonia, followed by intermolecular [5C + 1 N] aza-annulation reaction with a ketendithioacetal-based precursor, P-IQ. IQ displayed excellent recognition ability towards Hg2+ ions in H2O:ACN (99:1, v/v) via ICT-off fluorescent quenching behavior. Comparative FT-IR, 1H/13C NMR, mass spectral studies, and DFT analyses were carried out to validate the suggested mechanisms. Reversible studies confirm the secondary recognition effect of in-situ generated (IQ + Hg2+) complex on cysteine. The binding constant and LOD were estimated to be 3.7 × 104 M-1 and 0.86 µM, respectively. Further, IQ was utilized to evaluate the mercury ion content in real water samples demonstrating its effectiveness in water quality monitoring. The practical utility of IQ was further explored by developing TLC strips, Whatman filter-paper strips, and a low-cost, portable Arduino-based platform. Arduino microcontroller is interfaced with an RGB sensor to detect color changes and quantify mercury concentration w.r.t. RGB values.

New alkaloids and their in vitro antitumor activity of Corydalis balansae

The chemical investigation on Corydalis balansae resulted in the isolation of three previous undescribed compounds (1, 10, and 11) and 17 known compounds. Compound 1 and 2 were obtained as two lignanamide dimers, and compound 11 had a spiro [benzofuranone-benzazepine] skeleton, which was found in Corydalis for the first time. The structures of new compound were determined by the detailed analysis of 1D/2D NMR, UV, and IR data. Absolute configurations of compounds 10 and 11 were defined by their crystal X-ray diffraction data and calculations of electronic circular dichroism (ECD). The CCK-8 method was used to assay the inhibition effect of all the compounds on the growth of Hela, MGC-803, A549, and HepG2 cancer cells. Compound 2, 13, and 14 showed moderate inhibitory activity against the tested cell lines. Compound 2 exhibited potential antitumor activity against MGC-803 cells with an IC50 value of 20.8 μM, while the positive control etoposide was 17.3 μM. Furthermore, results from the cellular-mechanism investigation indicated that compound 2 could induce S-phase cell-cycle arrest and MGC-803 cells apoptosis, which was triggered by the up-regulation of PARP1, caspase-3 and -9, Bax, and down-regulation of Bcl-2. The 2-induced strong apoptosis indicated that compound 2 had good potential as an antitumor lead compound.

Isoquinoline alkaloids from the Corydalis tomentella with potential anti-hepatoma and antibacterial activities

Six undescribed isoquinolines, including one rarely reported N-benzyl isoquinoline together with sixteen known ones were isolated from C. tomentella. Their planar structures and absolute configurations were elucidated by extensive analyses of UV, IR, NMR, HRESIMS, DP4+ probability analysis as well as ECD calculations. Biological evaluations revealed that 3,4-2H-tomentelline C (6) showed significant cytotoxicity (IC₅₀ = 7.42 μM) against the HepG2 cell line while (1'R, 2'S)-coptichine B (3) exhibited stronger antibacterial activities.

SPION nanoparticles for delivery of dopaminergic isoquinoline and benzazepine derivatives

Superparamagnetic iron nanoparticles (SPIONs) have become one of the most useful colloidal systems in nanomedicine. We report here the preparation of new hybrid core@shell systems based on SPION nanoparticles coated with a SiO₂ shell (SPION@SiO₂) and functionalized with carboxyl groups (SPION@SiO₂-COOH). A series of new N-alkylamino- and N-alkylamido-terminated 1-phenyl- tetrahydroisoquinolines (THIQs) and 3-tetrahydrobenzazepines (THBs) derivatives presenting -SMe and -Cl groups, respectively, with potential dopaminergic activity, are synthesized and incorporated to the hybrid system. We include the synthetic details for THIQs and THBs derivatives preparation and investigate the influence of the terminal-functional group as well as the number of carbon atoms linked to THIQ and THB molecules during the coupling to the SPION@SiO₂-COOH. Nuclear magnetic resonance (NMR) and electron ionization mass spectrometry (EI-MS) are used to characterize the synthesized THIQs and THBs. High-angle annular dark-field transmission electron microscopy (HAADF-TEM), energy dispersive X-ray transmission electron microscopy (EDX-TEM), and proton high-resolution magic angle spinning NMR spectroscopy¹H HRMAS-NMR) are used to confirm the presence of THB and THIQ molecules onto the surface of the nanoparticles. The hybrid SPION@SiO₂-THIQ and THB systems show significant activity toward the D₂ receptor, reaching Ki values of about 20 nM, thus having potential application in the treatment of central nervous system (CNS) diseases.

Two new isoquinoline alkaloids from Cryptocarya wrayi and their biological activities

Two new isoquinoline alkaloids, cryptowrayines A (1) and B (2), along with one known pavine alkaloid (-)-12-hydroxyeschscholtzidine (3), were isolated from the twigs of Cryptocarya wrayi. The structures of new compounds were elucidated by extensive spectroscopic data analysis and electronic circular dichroism (ECD) calculations. Both compounds 1 and 2 exhibited moderate quinone reductase inducing activity in Hepa 1c1c7 cells.

Biosynthesis of Cu/KF/Clinoptilolite@MWCNTs nanocomposite and its application as a recyclable nanocatalyst for the synthesis of new Schiff base of benzoxazine derivatives and reduction of organic pollutants

In this work, we synthesized new Schiff base of benzoxazine derivatives in excellent yields using multicomponent reactions of phthalaldehyde or its derivatives, primary amines, isothiocyanate, 2,4-dihydroxyacetophenone, isopropenylacetylene and methyl or ethyl amine in the presence of catalytic amount of Cu/KF/CP@MWCNTs NCs in water at room temperature. Also, the catalytic activity of the green synthesized Cu/KF/CP@MWCNTs NCs was evaluated in the reduction in organic pollutants such as 4-nitrophenol (4-NP) in water at mild conditions. The results indicated that the biosynthesized NCs have very high and effective catalytic activity for organic pollutants within few seconds. As well the antioxidant activity of some synthesized benzoxazine was studied using trapping of radical by DPPH and ferric reduction activity potential (FRAP) experiment. The short time of reaction, high yields of product, easy separation of catalyst and products are some benefits of this procedure.

Isoquinolines: Important Cores in Many Marketed and Clinical Drugs

BACKGROUND

Isoquinoline analogs are an important, structurally diverse class of compounds that are extensively used as pharmaceuticals. Derivatives containing the isoquinoline scaffold have become a focus of therapeutic research because of their wide range of biological characteristics. Examples of these drugs, many of which are in clinical application or at the pre-clinical stage, are used to treat a broad swathe of ailments, such as tumors, respiratory diseases, infections, nervous system diseases, cardiovascular and cerebrovascular diseases, endocrine and metabolic diseases.

METHODS

Data were collected from PubMed, Web of Science, and SciFinder, through searches of drug names.

RESULTS

At least 38 isoquinoline-based therapeutic drugs are in clinical application or clinical trials, and their chemical structure and pharmacokinetics are described in detail.

CONCLUSION

The isoquinoline ring is a privileged scaffold which is often preferred as a structural basis for drug design, and plays an important role in drug discovery. This review provides a guide for pharmacologists to find effective preclinical/clinical drugs and examines recent progress in the application of the isoquinoline scaffold.

An insight into the medicinal attributes of berberine derivatives: A review

In the last few decades, traditional natural products have been the center of attention for the scientific community and exploration of their therapeutic abilities is proceeding perpetually. Berberine, with remarkable therapeutic diversity, is a plant derived isoquinoline alkaloid which is widely used as a traditional medicine in China. Berberine has been tackled as a fascinating pharmacophore to make great contributions to the discovery and development of new therapeutic agents against variegated diseases. Despite its tremendous therapeutic potential, clinical utility of this alkaloid was significantly compromised due to undesirable pharmacokinetic properties. To overcome this limitation, several structural modifications were performed on this scaffold to improve its therapeutic efficacy. The collective efforts of the community have achieved the tremendous advancements, bringing berberine to clinical use and discovering new therapeutic opportunities by structural modifications on the berberine scaffold. In this review, recent advancements in the medicinal chemistry of berberine and its derivatives in the last few years (2016-2020) have been compiled to represent inclusive data associated with various biological activities of this alkaloid. The comprehensive structure-activity relationship studies along with molecular modelling and mechanistic studies have also been summarized. This article would be highly helpful for the scientific community to get better insight into medicinal research of berberine and become a compelling guide for the rational design of berberine based compounds.

Antioxidant, anti-inflammatory, antibacterial, and analgesic activities and mechanisms of quinolines, indoles and related derivatives

Quinoline, isoquinoline and indoles are common heterocyclic compounds. They have many biological activities, such as antioxidant, anti-inflammatory, antibacterial, antitumor, anti-virus, anti-rheumatism, immunity regulation, expectorant, and analgesic. Over the past few centuries, traditional natural products have made great contributions to the discovery and development of new therapeutic agents. Many important drugs have been found from these three classes of compounds. In this mini-review, we mainly cover the research progress on antioxidant, anti-inflammatory, antibacterial, analgesic activities of quinoline, isoquinoline, and indole compounds over the past 20 years (2000-2019). We aim to explore new characteristic groups or structures in the search for active lead compounds and provide a basis for rational drug design.

An efficient diastereoselective synthesis of novel fused 5H-furo[2,3-d]thiazolo[3,2-a]pyrimidin-5-ones via one-pot three-component reaction

Herein, a convenient and efficient synthesis of 7-benzoyl-6-(aryl)-6,7-dihydro-5H-furo[2,3-d]thiazolo[3,2-a]pyrimidin-5-one derivatives was achieved from the reaction of isoquinolinium N-ylides, aromatic aldehydes, and heterocyclic 1,3-dicarbonyl compounds via one-pot three-component diastereoselective domino reaction in good-to-excellent yields. The advantages of this protocol are easily available starting materials, operational simplicity, and avoidance of hazardous organic solvents and catalyst. The synthesized products were characterized by IR, ¹H NMR, ¹³C NMR and mass spectra. Additionally, the conclusive structure of target compounds was confirmed by X-Ray diffraction analysis.

Fluorimetric Detection of Zn2+, Mg2+, and Fe2+ with 3-Hydroxy-4-Pyridylisoquinoline as Fluorescent Probe

The suitability of 3-hydroxy-4-pyridylisoquinoline to operate as fluorescent chemosensor for the detection of metal ions was investigated. For that purpose, the interactions of the title compound with selected metal ions were investigated by absorption and emission spectroscopy. The complexation of Zn²⁺, Fe²⁺, Mg²⁺ with 1:1 and 2:1 stoichiometry leads to characteristic optical responses that depend significantly on the employed solvents, thus allowing for the fluorimetric identification and detection of particular metal cations in a matrix-based pattern analysis or by fluorimetric titrations.

Highly selective and sensitive chemosensor for Al(III) based on isoquinoline Schiff base

As a colorimetric and fluorescent turn-on sensor to Al³⁺, N'-(2-hydroxybenzylidene)isoquinoline-3-carbohydrazide (HL) has been easily synthesized. The fluorescence intensity increases by 273 times in the presence of Al³⁺ at 458 nm. Meanwhile, the experiment data indicate that the limit of detection for Al³⁺ is 1.11 × 10^-9 M. Remarkably, the blue fluorescence signal of HL-Al³⁺ could be specially observed by the naked eye under UV light and is significantly different from those of other metal ions. Fluorescence switch based on the control of Al³⁺ and EDTA proved HL could act as a reversible chemosensor. According to ESI-MS result and the Job's plots, the 2:1 coordination complex formed by HL and Al³⁺ could be produced. Density functional theory calculations were performed to illustrate the structures of HL and complex. The cell imaging experiment indicates that HL can be applied for monitoring intracellular Al³⁺ levels in cells.

An Overview of Privileged Scaffold: Quinolines and Isoquinolines in Medicinal Chemistry as Anticancer Agents

Cancer is one of the most difficult diseases and causes of death for many decades. Many pieces of research are continuously going on to get a solution for cancer. Quinoline and isoquinoline derivatives have shown their possibilities to work as an antitumor agent in anticancer treatment. The members of this privileged scaffold quinoline and isoquinoline have shown their controlling impacts on cancer treatment through various modes. In particular, this review suggests the current scenario of quinoline and isoquinoline derivatives as antitumor agents and refine the path of these derivatives to find and develop new drugs against an evil known as cancer.

Betulinic acid derived amides are highly cytotoxic, apoptotic and selective

Betulinic and platanic acid derived amides were prepared and screened for their cytotoxic activity. All of the compounds were shown to be cytotoxic for a panel of human tumor cell lines, and especially apoptotic betulinic acid derived compounds 6, 8 and 19 showed low EC₅₀ values. Of special interest was a 4-isoquinolinyl amide of 3-O-acetyl-betulinic acid (compound 19), being the most cytotoxic compound of this series and holding EC₅₀ values as low as EC₅₀ = 1.48 μM (A375 melanoma cells) while being significantly less cytotoxic for non-malignant fibroblasts NIH 3T3 with a selectivity index of >91.2. This finding parallels previous results obtained for SAA21, a augustic acid derived compound thus making the 4-isoquinolinyl moiety to a privileged scaffold.

Novel cyclometalated Ru(II) complexes containing isoquinoline ligands: Synthesis, characterization, cellular uptake and in vitro cytotoxicity

Two novel cyclometalated Ru(II) complexes containing isoquinoline ligand, [Ru(bpy)₂(1-Ph-IQ)](PF₆), (bpy = 2,2'-bipyridine; 1-Ph-IQ = 1-phenylisoquinoline; RuIQ-1) and [Ru(phen)₂(1-Ph-IQ)](PF₆) (phen = 1,10-phenanthroline; RuIQ-2) were found to show high cytotoxic activity against NCI-H460, A549, HeLa and MCF-7 cell lines. Notably, both of them exhibited IC₅₀ values that were an order of magnitude lower than those of clinical cisplatin and two structurally similar Ru(II)-isoquinoline complexes [Ru(bpy)₂(1-Py-IQ)](PF₆)₂ (Ru3) and [Ru(phen)₂(1-Py-IQ)](PF₆)₂ (Ru4) (1-Py-IQ = 1-pyridine-2-yl). The cellular uptake and intracellular localization displayed that the two cyclometalated Ru(II) complexes entered NCI-H460 cancer cells dominantly via endocytosis pathway, and preferentially distributed in the nucleus. Further investigations on the apoptosis-inducing mechanisms of RuIQ-1 and RuIQ-2 revealed that the two complexes could cause S, G2/M double-cycle arrest by regulating cell cycle related proteins. The two complexes also could reduce the mitochondrial membrane potential (MMP), promote the generation of intracellular ROS and trigger DNA damage, and then lead to apoptosis-mediated cell death. More importantly, RuIQ-2 exhibits low toxicity both towards normal HBE cells in vitro and zebrafish embryos in vivo. Accordingly, the developed complexes hold great potential to be developed as novel therapeutics for effective and low-toxic cancer treatment.

Clinical evaluation of [18F] JNJ-64326067, a novel candidate PET tracer for the detection of tau pathology in Alzheimer's disease

PURPOSE

The accumulation of misfolded tau is a common feature of several neurodegenerative disorders, with Alzheimer's disease (AD) being the most common. Earlier we identified JNJ-64326067, a novel isoquinoline derivative with high affinity and selectivity for tau aggregates from human AD brain. We report the dosimetry of [¹⁸F] JNJ-64326067 and results of a proof-of-concept study comparing subjects with probable Alzheimer's disease to age-matched healthy controls.

METHODS

[¹⁸F] JNJ-64326067 PET scans were acquired for 90 min and then from 120 to 180 min in 5 participants with [¹⁸F]-florbetapir PET amyloid positive probable AD (73 ± 9 years) and 5 [¹⁸F]-florbetapir PET amyloid negative healthy controls (71 ± 7 years). Whole-body [¹⁸F] JNJ-64326067 PET CT scans were acquired in six healthy subjects for 5.5 h in 3 scanning sessions. Brain PET scans were visually reviewed. Regional quantification included kinetic analysis of distribution volume ration (DVR) estimated by Logan graphical analysis over the entire scan and static analysis of SUVr in late frames. Both methods used ventral cerebellar cortex as a reference region.

RESULTS

One of the healthy controls had focal areas of PET signal in occipital and parietal cortex underlying the site of a gunshot injury as an adolescent; the other four healthy subjects had no tau brain signal. Four of the 5 AD participants had visually apparent retention of [¹⁸F] JNJ-64326067 in relevant cortical regions. One of the AD subjects was visually negative. Cortical signal in visually positive subjects approached steady state by 120 min. Temporal and frontal cortical SUVr/DVR values in visually positive AD subjects ranged from 1.21 to 3.09/1.2 to 2.18 and from 0.92 to 1.28/0.91 to 1.16 in healthy controls. Whole-body effective dose was estimated to be 0.0257 mSv/MBq for females and 0.0254 mSv/MBq for males.

CONCLUSIONS

[¹⁸F] JNJ-64326067 could be useful for detection and quantitation of tau aggregates.

Simple analogues of natural product chelerythrine: Discovery of a novel anticholinesterase 2-phenylisoquinolin-2-ium scaffold with excellent potency against acetylcholinesterase

As simple analogues of the natural compound chelerythrine, a novel anti-cholinesterase 2-phenylisoquinolin-2-ium scaffold was designed by structure imitation. The activity evaluation led to the discovery of seven compounds with potent anti-acetylcholinesterase activity with IC₅₀ values of ≤0.72 μM, superior to chelerythrine and standard drugs galantamine. Particularly, compound 8y showed the excellent dual acetylcholinesterase-butyrylcholinesterase inhibition activity, superior to rivastigmine, a dual cholinesterase inhibitor drug. Furthermore, the compounds displayed a competitive anti-acetylcholinesterase mechanism with the substrate and low cytotoxicity. Molecular docking showed that the isoquinoline moiety is embedded in a cavity surrounded by four aromatic residues of acetylcholinesterase by the π-π action. Structure-activity relationship showed that the p-substituents on the C-ring can dramatically improve the anti-acetylcholinesterase activity, while 8-OMe can increase the activity against the two cholinesterases simultaneously. Thus, the title compounds emerged as promising lead compounds for the development of novel cholinesterase inhibitor agents.

Dopaminergic system contribution to the antidepressant-like effect of 3-phenyl-4-(phenylseleno) isoquinoline in mice

Depression is a serious disorder characterized by imbalance of mood and emotions, which is accompanied by the reduction in the monoaminergic signaling. The monoamine oxidase inhibition could lead to an increase in monoaminergic neurotransmitter levels in the brain. According to our previous study, 3-phenyl-4-(phenylseleno) isoquinoline (PSI) is a selective and reversible MAO-B inhibitor in vitro. The present study investigated the putative ex vivo inhibitory effect of a single PSI dose on the cerebral MAO activity and its antidepressant-like action in the mouse forced swimming test (FST). Additionally, the dopaminergic system contribution to the antidepressant-like effect of PSI was also evaluated. For this, PSI was dissolved in canola oil to determine time-course (0.5-24 h) and dose-response (25-100 mg/kg, 10 ml/kg, intragastrically) curves of MAO activity inhibition using adult C57Bl/6 male mice. A single PSI dose of 100 mg/kg inhibited the MAO-B activity in the whole brain 8 h after administration to mice, while it did not alter the MAO-A activity. The FST was carried out 0.5, 8, and 24 h after the PSI administration (100 mg/kg) or vehicle, but its antidepressant-like effect was demonstrated only at 0.5 and 8 h after treatment. Lastly, the contribution of dopaminergic system in the PSI antidepressant-like effect was demonstrated by using dopamine receptors antagonists, SCH23390, haloperidol and sulpiride. Thus, a single PSI dose of 100 mg/kg had an antidepressant-like effect in mice subjected to the FST 0.5 and 8 h after its administration. Moreover, the inhibition of cerebral MAO-B activity and modulation of dopamine receptors contributed to the antidepressant-like effect of PSI in mice.

Dipolar cycloaddition strategy for three-component synthesis of chromeno[3',4':3,4]pyrido[2,1-a]isoquinoline derivatives

A rapid and efficient protocol to fused pentacyclic compounds, the chromeno[3',4':3,4]pyrido[2,1-a]isoquinolines, via a diastereoselective 1,4-dipolar cycloaddition reaction of isoquinoline, dialkyl acetylenedicarboxylates, and 3-acetyl coumarins, is described.

Contribution of cholinergic system and Nrf2/HO-1 signaling to the anti-amnesic action of 7-fluoro-1,3-diphenylisoquinoline-1-amine in mice

The isoquinoline 7-fluoro-1,3-diphenylisoquinoline-1-amine (FDPI) has been studied due to its multitarget properties, such as modulation of GABAergic and glutamatergic systems, antioxidant, and anti-inflammatory. This study investigated the contribution of oxidative stress, nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/heme oxygenase (HO-1) signaling, and the cholinergic system to the anti-amnesic action of FDPI in mice. Adult male Swiss mice received FDPI for 5 days (5-25 mg/kg, i.g.); the animals received scopolamine (1 mg/kg, i.p) from day 3-5. The vehicle-control group was carried out. Afterward, mice performed object recognition tests (ORTs). Scopolamine induced amnesia and cholinergic dysfunction by increasing the acetylcholinesterase (AChE) activity and content, decreasing the muscarinic M1 receptor levels in the prefrontal cortex and hippocampus of mice. This study reveals that scopolamine altered oxidative stress parameters differently in the prefrontal cortex and hippocampus of mice. Whereas the prefrontal cortex was susceptible to oxidative stress, none of the parameters evaluated was altered in the hippocampus of scopolamine-treated mice. FDPI at doses of 10 and 25 mg/kg had an anti-amnesic effect in the ORT tests. FDPI 10 mg/kg reversed the increase in the AChE activity and content, oxidative stress parameters, and modulated Nrf2/HO-1 signaling in the prefrontal cortex of scopolamine-exposed mice. Pearson's correlation analyses reinforced the contribution of the prefrontal cortical cholinergic system, oxidative stress as well as Nrf2/HO-1 signaling in the anti-amnesic effect of FDPI. Considering FDPI effects on the hippocampus, it was effective against the cholinergic dysfunction, AChE activity and content, and M1 receptor levels, which collectively could contribute to its anti-amnesic effect.

Isoquinoline-based biaryls as a robust scaffold for microtubule inhibitors

We here report the discovery of isoquinoline-based biaryls as a new scaffold for colchicine domain tubulin inhibitors. Colchicinoid inhibitors offer highly desirable cytotoxic and vascular disrupting bioactivities, but their further development requires improving in vivo robustness and tolerability: properties that both depend on the scaffold structure employed. We have developed isoquinoline-based biaryls as a novel scaffold for high-potency tubulin inhibitors, with excellent robustness, druglikeness, and facile late-stage structural diversification, accessible through a tolerant synthetic route. We confirmed their bioactivity mechanism in vitro, developed soluble prodrugs, and established safe in vivo dosing in mice. By addressing several problems facing the current families of inhibitors, we expect that this new scaffold will find a range of in vivo applications towards translational use in cancer therapy.

In vitro and in vivo anti-tumor activity of two gold(III) complexes with isoquinoline derivatives as ligands

Two gold(III) complexes of isoquinoline derivatives: [Au(L¹)Cl₂] (Au1) and [Au(L²)Cl₂] (Au2) have been prepared and characterized. Au1 and Au2 exhibited greater cytotoxicity than their corresponding ligands and cisplatin against T-24 cells. Both complexes arrested cell cycle at S-phase by upregulation of p53, p27, and p21, and downregulation of cyclin A and cyclin E. The depolarization of the mitochondrial membrane potential, generation of ROS, and stimulated Ca²⁺ release activated the caspase cascade and ultimately caused apoptosis by increasing the levels of Bax and Bak, and decreasing the levels of Bcl-2 and Bcl-xl. Cell apoptosis was achieved via mitochondria mediated pathways. The in vivo studies of Au1 and Au2 demonstrated that they were safer than cisplatin and could effectively inhibit tumor growth.

Isoquinolines from Corydalis tomentella from Tibet, China, possess hepatoprotective activities

The phytochemical study on Corydalis tomentella Franch, a traditional Chinese medicinal plant in Tibet, China, led to the isolation of six previously undescribed isoquinolines, including two rarely reported N-benzyl ones, and twenty-one known ones firstly obtained from this plant. Their planar structures were elucidated by 1D, 2D NMR experiments and high resolution mass spectrometry, and the absolute configurations were determined by NOE experiments, electronic circular dichroism, and specific rotation. Seven isoquinolines exhibited stronger hepatoprotective activities than that of positive control in D-galactosamine induced L02 cells damage model, which could be served as the leading compounds for further investigations. The primary structure-activity relationship was also summarized accordingly.

Discovery of new potent protein arginine methyltransferase 5 (PRMT5) inhibitors by assembly of key pharmacophores from known inhibitors

Protein arginine methyltransferase 5 (PRMT5) is an epigenetics related enzyme that has been validated as a promising therapeutic target for human cancer. Up to now, two small molecule PRMT5 inhibitors has been put into phase I clinical trial. In the present study, a series of candidate molecules were designed by combining key pharmacophores of formerly reported PRMT5 inhibitors. The in vitro PRMT5 inhibitory testing of compound 4b14 revealed an IC₅₀ of 2.71 μM, exhibiting high selectivity over PRMT1 and PRMT4 (>70-fold selective). As expected, 4b14 exhibited potent anti-proliferative activity against a panel of leukemia and lymphoma cells, including MV4-11, Pfeiffer, SU-DHL-4 and KARPAS-422. Besides, 4b14 showed significant cell cycle arrest and apoptosis-inducing effects, as well as reduced the cellular symmetric arginine dimethylation level of SmD3 protein. Finally, affinity profiling analysis indicated that hydrophobic interactions, π-π stacking and cation-π actions made the major contributions to the overall binding affinity. This scaffold provides a new chemical template for further development of better lead compounds targeting PRMT5.

7-Fluoro-1,3-diphenylisoquinoline reverses motor and non-motor symptoms induced by MPTP in mice: Role of striatal neuroinflammation

Parkinson's disease (PD) is a dopaminergic neurodegenerative disorder, which presents motor and non-motor symptoms. 7-Fluoro-1,3-diphenylisoquinoline (FDPI) is an isoquinoline compound with antioxidant and antidepressant properties. This study investigated whether FDPI reverses motor and non-motor symptoms in an acute mouse model of PD induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). It was also assessed the anti-inflammatory mechanisms in FDPI pharmacological action. C57Bl/6 male adult mice received four MPTP (20mg/kg, intraperitoneal) or saline (vehicle) injections to induce an acute PD model. FDPI (10mg/kg, intragastric) was daily administered to mice from the 2nd to 9th day after the induction and mice performed the behavioral tests on the 8th and 9th days. Striatum samples were collected for biochemical and molecular analyses. The results of the rotarod and challenging beam tests demonstrated that the administration of FDPI attenuated the impairments in balance and coordination of mice induced by MPTP. The FDPI reversed the short-term memory deficit and depressive-like behavior induced by MPTP in mice. FDPI attenuated the reduction in the striatal tyrosine hydroxylase levels, and it reversed the increase in the cyclooxygenase-2 levels and myeloperoxidase activity caused by MPTP in mice. Therefore, FDPI reversed motor and non-motor symptoms induced by an acute PD model and its restorative effects seem to be mediated by an anti-inflammatory action associated with a modulation of the striatal cyclooxygenase-2 levels and myeloperoxidase activity.

Brain-derived neurotrophic factor signaling plays a role in resilience to stress promoted by isoquinoline in defeated mice

Certain stressful life events have been associated with the onset of depression. This study aims to investigate if 7-fluoro-1,3-diphenylisoquinoline-1-amine (FDPI) is effective against social avoidance induced by social defeat stress model in mice. Furthermore, it was investigated the effects of FDPI in the mouse prefrontal cortical plasticity-related proteins and some parameters of toxicity. Adult Swiss mice were subjected to social defeat stress for 10 days. Two protocols with FDPI were carried out: 1- FDPI (25 mg/kg, intragastric) was administered to mice 24 h after the last social defeat stress episode; 2- FDPI (1-25 mg/kg, intragastric) was administered to mice once a day for 10 days concomitant with the social defeat stress. The mice performed social avoidance and locomotor tests. The prefrontal cortical protein contents of kinase B (Akt), extracellular signal-regulated kinase (ERK), cAMP-response element binding protein (CREB), pro-brain-derived neurotrophic factor (proBDNF), p75^NTR, neuronal nuclear protein (NeuN) and nuclear factor-κB (NF-κB) were determined in mice. A single administration of FDPI (25 mg/kg) partially protected against social avoidance induced by stress in mice. Repeated administration of FDPI (25 mg/kg) protected against social avoidance induced by stress in mice. Social defeat stress decreased the protein contents of p75^NTR, NeuN and the pERK/ERK ratio but increased those of proBDNF and the pCREB/CREB ratio, without changing that of NF-κB. Repeated administration of FDPI modulated signaling pathways altered by social defeat stress in mice. The present findings demonstrate that FDPI promoted resilience to stress in mice.

System Biology Approach to Identify Potential Receptor for Targeting Cancer and Biomolecular Interaction Studies of Indole[2,1-a]Isoquinoline Derivative as Anticancerous Drug Candidate Against it

Cancer is a public health concern which is spreading throughout the world. Different approaches have been employed to combat this disease. System biology approach has been used to understand the molecular mechanisms of drugs targeting cancer cell's receptor which have opened-up a window to develop effective drugs for it. We have demonstrated biomolecular interaction studies using the rational drug design of indole[2,1-a]isoquinoline derivative as a potent inhibitor against identified cancerous protein PIK3CA -a catalytic sub-unit of PI3K family protein-and compared its affinity with FDA approved drugs for receptors such as dactolisib, idelalisib, and several others such afatinib, avastin, ceritinib and crizotinib, etc.; by docking against potential receptor to set a cutoff value for our screening. Isoquinolines are small alkaloids with a vast variety of substitution depending upon their biogenetic pattern. Isoquinoline derivatives have been reported for their antimalarial, antibacterial, antifungal and anticancerous activities. The results obtained from the present studies conclude that membrane protein is an efficient drug that can be used to target cancer. Moreover, comparative study with ADMET prediction concludes that isoquinoline can be a potent drug for cancer treatment.

7-Fluoro-1,3-diphenylisoquinoline-1-amine reverses the reduction in self-care behavior induced by maternal separation stress in rats by modulating glutamatergic/GABAergic systems

7-Fluoro-1,3-diphenylisoquinoline-1-amine (FDPI) is a promising isoquinoline that elicits an antidepressant-like action in rodents. In this study, an animal model of stress induced by maternal separation was used to investigate the effects of FDPI in Wistar rats of 30 and 90 days of age. It was investigated the effects of maternal separation in the self-care behavior and the contribution of glutamatergic and gamma-aminobutyric acid (GABA)ergic systems in the FDPI action. Male Wistar rats were separated from their mothers for 3 h/day from postnatal day (PND) 1-10. The rats were treated at different ages (PND-30 and PND-90) with FDPI (5 mg/kg, intragastrically/7 days) and performed the splash test. Maternal separation reduced total grooming time in the splash test, an index of motivational and self-care behavior, and FDPI treatment was effective in reversing this behavior in rats at both ages. The neurochemical parameters were differently affected, dependent on the age of rats, by maternal separation and FDPI. Maternal separation increased the GABA uptake and the excitatory amino acid transporter 1 levels in the prefrontal cortices of rats at PND-30 and FDPI was effective against these alterations. At PND-90, maternal separation decreased the glutamate uptake and increased the GABA uptake and the N-methyl-D-aspartate (NMDA) receptor 2B levels in the prefrontal cortices of rats. FDPI reversed the neurochemical alterations caused by maternal separation in the prefrontal cortices of rats at PND-90. The results of this study demonstrated that FDPI reversed the reduction in self-care behavior induced by maternal separation stress in rats by modulating the glutamatergic/GABAergic systems in rats.

Cytotoxic activity, apoptosis induction and structure-activity relationship of 8-OR-2-aryl-3,4-dihydroisoquinolin-2-ium salts as promising anticancer agents

As our continuing research, a series of 2-aryl-8-OR-3,4-dihydroisoquinolin-2-ium bromides were evaluated for cytotoxic activity on cancer cells and apoptosis induction in the present study. SAR was derived also. Among them, 23 compounds showed the higher cytotoxicity on MKN-45 cells with IC₅₀ values of 1.99-11.3μM than a standard anticancer drug cis-platinum (IC₅₀=11.4μM) or their natural model compound chelerythrine (IC₅₀=12.7μM); 16 compounds possessed the medium to high activity on NB4 cells with IC₅₀ values of 1.67-4.62μM. SAR analysis showed that both substitution patterns of the N-aromatic ring and the type of 8-OR significantly impact the activity. AO/EB staining and flow cytometry analysis with Annexin V/PI double staining showed that the compounds were able to induce apoptosis in a concentration-dependent manner. The results above suggested that the title compounds are a class of promising compounds for the development of new anti-cancer drugs.

Synthesis, bioactivity and structure-activity relationships of new 2-aryl-8-OR-3,4-dihydroisoquinolin-2-iums salts as potential antifungal agents

As our continuing research on antifungal dihydroisoquinolin-2-ium salts, forty 2-aryl-8-OR-3,4-dihydroisoquinolin-2-ium bromides were synthesized and characterized by spectroscopic analysis. By using the mycelium growth rate method, the compounds were evaluated for antifungal activity against three plant pathogenic fungi and structure-activity relationships (SAR) were derived. The vast majority of the compounds displayed the medium to high activity with inhibition rates of 50-100% at 150μM. About half of the compounds were more active than their natural model compounds sanguinarine and chelerythrine for all the fungi, and part or most of them were more active than positive drugs thiabendazole and azoxystrobin. SAR analysis showed that both substitution patterns of the C-ring and the type of 8-OR group significantly influenced the activity. Thus, a series of new title compounds with excellent antifungal potency emerged.

Contribution of NMDA, GABAA and GABAB receptors and l-arginine-NO-cGMP, MEK1/2 and CaMK-II pathways in the antidepressant-like effect of 7-fluoro-1,3-diphenylisoquinoline-1-amine in mice

It has been reported that the antidepressant-like effect of 7-fluoro-1,3-diphenylisoquinoline-1-amine (FDPI) may result from the modulation of brain monoaminergic systems. However, the mechanisms of FDPI action are not fully understood. The aim of this study was to investigate the contribution of N-methyl-d-aspartate (NMDA) and gamma-aminobutyric acid (GABA) systems as well as l-arginine-nitric oxide-(NO)-cyclic guanosine monophosphate-(cGMP), mitogen-activated protein/extracellular signal-regulated kinase (MEK1/2) and Ca(2+)/calmodulin-dependent protein kinase II (CaMK-II) signaling pathways in the antidepressant-like effect of FDPI in the mouse forced swimming test (FST). The levels of NO and uptake of [(3)H]glutamate and [(3)H]GABA were determined in prefrontal cortices of Swiss mice. Pretreatments with NMDA (0.1 pmol/site, i.c.v., a NMDA receptor agonist), bicuculline (1mg/kg, i.p., a GABAA receptor antagonist), phaclofen (2mg/kg, i.p., a GABAB receptor antagonist) and l-arginine (750mg/kg, i.p., a NO precursor), KN-62 (1μg/site, a CaMK-II inhibitor), U0126 (5μg/site, a MEK1/2 inhibitor) and PD09058 (5μg/site, a MEK1/2 inhibitor) blocked the antidepressant-like effect of FDPI, at a dose of 1mg/kg, in the FST. ODQ (30 pmol/site, i.c.v., a soluble guanylate cyclase (sGC) inhibitor) in combination with a sub-effective dose of FDPI (0.1mg/kg, i.g.) reduced the immobility time in the FST. The administration of FDPI (50mg/kg) to mice increased the glutamate uptake and reduced NO levels in the prefrontal cortex of mice. The results suggest a contribution of NMDA, GABAA and GABAB receptors and l-arginine-NO-cGMP pathway in the antidepressant-like action of FDPI in mice, and this effect is related to CaMK-II and MEK 1/2 activation.

A novel isoquinoline compound abolishes chronic unpredictable mild stress-induced depressive-like behavior in mice

Chronic unpredictable mild stress (CUMS) elicits aspects of cognitive and behavioral alterations that can be used to model comparable aspects of depression in humans. The aim of the present study was to investigate the antidepressant-like potential of 7-fluoro-1,3-diphenylisoquinoline-1-amine (FDPI), a novel isoquinoline compound, in CUMS, a model that meets face, construct and predictive criteria for validity. Swiss mice were subjected to different stress paradigms daily for a period of 35 days to induce the depressive-like behavior. The animals received concomitant FDPI (0.1 and 1mg/kg, intragastric) or paroxetine (8mg/kg, intraperitoneal) and CUMS. The behavioral tests (splash test, tail suspension test, modified forced swimming test and locomotor activity) were performed. The levels of cytokines, corticosterone and adrenocorticotropic (ACTH) hormones were determined in the mouse prefrontal cortex and serum. The synaptosomal [(3)H] serotonin (5-HT) uptake, nuclear factor (NF)-κB, tyrosine kinase receptor (TrkB) and pro-brain-derived neurotrophic factor (BDNF) levels were determined in the mouse prefrontal cortex. CUMS induced a depressive-like behavior in mice, which was demonstrated in the modified forced swimming, tail suspension and splash tests. FDPI at both doses prevented depressive-like behavior induced by CUMS, without altering the locomotor activity of mice. FDPI at the highest dose prevented the increase in the levels of NF-kB, pro-inflammatory cytokines, corticosterone and ACTH and modulated [(3)H]5-HT uptake and the proBDNF/TrkB signaling pathway altered by CUMS. The present findings demonstrated that FDPI elicited an antidepressant-like effect in a model of stress-induced depression.

One-Pot Synthesis, Spectroscopic and Physicochemical Studies of Quinoline Based Blue Emitting Donor-Acceptor Chromophores with Their Biological Application

Blue emitting cyano substituted isoquinoline dyes were synthesized by one-pot multicomponent reactions (MCRs) of aldehydes, malononitrile, 6-methoxy-1,2,3,4-tetrahydro-naphthalin-1-one and ammonium acetate. Results obtained from spectroscopic (FT-IR, (1)H-NMR, (13)C-NMR, EI-MS) and elemental analysis of synthesized compounds was in good agreement with their chemical structures. UV-vis and fluorescence spectroscopy measurements proved that all compounds are good absorbent and fluorescent. Fluorescence polarity study demonstrated that these compounds were sensitive to the polarity of the microenvironment provided by different solvents. In addition, spectroscopic and physicochemical parameters, including electronic absorption, excitation coefficient, stokes shift, oscillator strength, transition dipole moment and fluorescence quantum yield were investigated in order to explore the analytical potential of synthesized compounds. The anti-bacterial activity of these compounds were first studied in vitro by the disk diffusion assay against two Gram-positive and two Gram-negative bacteria then the minimum inhibitory concentration (MIC) was determined with the reference of standard drug chloramphenicol. The results displayed that compound 3 was better inhibitors of both types of the bacteria (Gram-positive and Gram-negative) than chloramphenicol. Graphical Abstract ᅟ.

A novel GABA(A) alpha 5 receptor inhibitor with therapeutic potential

Novel 2,3-benzodiazepine and related isoquinoline derivatives, substituted at position 1 with a 2-benzothiophenyl moiety, were synthesized to produce compounds that potently inhibited the action of GABA on heterologously expressed GABAA receptors containing the alpha 5 subunit (GABAA α5), with no apparent affinity for the benzodiazepine site. Substitutions of the benzothiophene moiety at position 4 led to compounds with drug-like properties that were putative inhibitors of extra-synaptic GABAA α5 receptors and had substantial blood-brain barrier permeability. Initial characterization in vivo showed that 8-methyl-5-[4-(trifluoromethyl)-1-benzothiophen-2-yl]-1,9-dihydro-2H-[1,3]oxazolo[4,5-h][2,3]benzodiazepin-2-one was devoid of sedative, pro-convulsive or motor side-effects, and enhanced the performance of rats in the object recognition test. In summary, we have discovered a first-in-class GABA-site inhibitor of extra-synaptic GABAA α5 receptors that has promising drug-like properties and warrants further development.

Design, synthesis and biological evaluation of isoquinoline-based derivatives as novel histone deacetylase inhibitors

The design, synthesis and biological evaluation of a series of isoquinoline-based hydroxamic acid compounds as novel HDACs inhibitors were reported herein. A detailed SAR study showed most of the compounds displayed good to excellent inhibitory activities against HDAC1, 3, 6. The IC50 values of compound 10 c against HDAC1, 3, 6 were 4.17 ± 0.11 nM, 4.00 ± 0.10 nM, 3.77 ± 0.07 nM, respectively. Most of the compounds showed great anti-proliferative activities against RPMI 8226, HCT 116 and Hep G2 cells. The IC50 values of compounds 10 a-h against RPMI 8226 cancer cell proliferation were all below 1 μM. HCT 116 cell was sensitive to the compounds 10 a, 10 f-g and 18 a with the IC50 values <0.3 μM. The active compounds 10a-d did not show inhibitory activity against hERG channel. All these evidence indicated these compounds had great potential as HDACs inhibitors for the further development.

Naturally occurring plant isoquinoline N-oxide alkaloids: their pharmacological and SAR activities

The present review describes research on novel natural isoquinoline alkaloids and their N-oxides isolated from different plant species. More than 200 biological active compounds have shown confirmed antimicrobial, antibacterial, antitumor, and other activities. The structures, origins, and reported biological activities of a selection of isoquinoline N-oxides alkaloids are reviewed. With the computer program PASS some additional SAR (structure-activity relationship) activities are also predicted, which point toward new possible applications of these compounds. This review emphasizes the role of isoquinoline N-oxides alkaloids as an important source of leads for drug discovery.

Pseudocyanides of sanguinarine and chelerythrine and their series of structurally simple analogues as new anticancer lead compounds: Cytotoxic activity, structure-activity relationship and apoptosis induction

6-Cyano dihydrosanguinarine (CNS) and 6-cyano dihydrochelerythrine (CNC) are respectively artificial derivatives of sanguinarine and chelerythrine, two anticancer quaternary benzo[c]phenanthridine alkaloids (QBAs) while 1-cyano-2-aryl-1,2,3,4-tetrahydroisoquinolines (CATHIQs) are a class of structurally simple analogues of CNS or CNC. This study investigated the inhibition activity of CNS, CNC and CATHIQs on cancer cells, apoptosis induction as well as their preliminary SAR. The results showed that CNS and 18 out of CATHIQs showed IC50 values of 0.53 and 0.62-2.24μM against NB4 and 1.53 and 2.99-11.17μM against MKN-45 cells, respectively, superior to a standard anticancer drug cis-platinum with IC50 of 2.39 and 11.36μM. CNC showed a higher activity against NB4 cells (IC50=1.85μM) and a moderate activity against MKN-45 cells (IC50=12.72μM). Among all CATHIQs, 2 and 17 gave the highest activity against NB4 cells and MKN-45 cells (IC50=0.62 and 2.99μM), respectively. DAPI staining, AO/EB staining and ultrastructure analysis of cells demonstrated that CATHIQs were able to induce apoptosis of the cells in a concentration-dependent manner. SAR showed that substitution patterns on the N-aromatic ring significantly influenced the activity of CATHIQs. The general trend was that the introduction of electron-withdrawing substituents like halogen atom, nitro, trifluoromethyl led to a significant improvement of the activity, while the presence of electron-donating groups like methyl, methoxyl caused a reduction of the activity. In most cases, the 2' site was the most favorable substitution position for the improvement of the activity. Thus, the present results strongly suggested that QBA-type pseudocyanides may serve as potential alternatives of anticancer QBAs while CATHIQs should be a class of promising lead compounds for the development of new QBA-like-type anticancer drugs. CNS exhibited the highest cytotoxicities with IC50 values of 0.53μM on NB4 cells and 1.53μM on MKN-45 cells.

Isoquinoline alkaloids as a novel type of AKR1C3 inhibitors

AKR1C3 is an important human enzyme that participates in the reduction of steroids and prostaglandins, which leads to proliferative signalling. In addition, this enzyme also participates in the biotransformation of xenobiotics, such as drugs and procarcinogens. AKR1C3 is involved in the development of both hormone-dependent and hormone-independent cancers and was recently demonstrated to confer cell resistance to anthracyclines. Because AKR1C3 is frequently upregulated in various cancers, this enzyme has been suggested as a therapeutic target for the treatment of these pathological conditions. In this study, nineteen isoquinoline alkaloids were examined for their ability to inhibit a recombinant AKR1C3 enzyme. As a result, stylopine was demonstrated to be the most potent inhibitor among the tested compounds and exhibited moderate selectivity towards AKR1C3. In the follow-up cellular studies, stylopine significantly inhibited the AKR1C3-mediated reduction of daunorubicin in intact cells without considerable cytotoxic effects. This inhibitor could therefore be used as a model AKR1C3 inhibitor in research or evaluated as a possible therapeutic anticancer drug. Furthermore, based on our results, stylopine can serve as a model compound for the design and future development of structurally related AKR1C3 inhibitors.

Design, synthesis and molecular docking studies of novel N-benzenesulfonyl-1,2,3,4-tetrahydroisoquinoline-based triazoles with potential anticancer activity

A novel series of N-benzenesulfonyl-1,2,3,4-tetrahydroisoquinolines (14-33) containing triazole moiety were designed and synthesized through rational cycloadditions using the modified Pictet-Spengler reaction and the Click chemistry. Antiproliferative activity against four cancer cell lines (e.g., HuCCA-1, HepG2, A549 and MOLT-3) revealed that many substituted triazole analogs of benzoates (20, 29) and benzaldehydes (30, 32) exhibited anticancer activity against all of the tested cancer cell lines in which the ester analog 20 was shown to be the most potent compound against HuCCA-1 (IC50 = 0.63 μM) and A549 (IC50 = 0.57 μM) cell lines. Triazoles bearing phenyl (15, 24), tolyl (26, 27), acetophenone (19), benzoate (20, 29), benzaldehyde (21, 30) and naphthalenyl (25) substituents showed stronger anticancer activity against HepG2 cells than that of the etoposide. Interestingly, the p-tolyl analog (27) displayed the most potent inhibitory activity (IC50 = 0.56 μM) against HepG2 cells without affecting normal cells. Of the investigated tetrahydroisoquinoline-triazoles, the promising compounds 20 and 27 were selected for molecular docking against AKR1C3, which was identified to be a plausible target site.