Polycyclic cage structures as lipophilic scaffolds for neuroactive drugs

Therapeutic Role of Heterocyclic Compounds in Neurodegenerative Diseases: Insights from Alzheimer's and Parkinson's Diseases

Alzheimer's and Parkinson's are the most common neurodegenerative diseases (NDDs). The development of aberrant protein aggregates and the progressive and permanent loss of neurons are the major characteristic features of these disorders. Although the precise mechanisms causing Alzheimer's disease (AD) and Parkinson's disease (PD) are still unknown, there is a wealth of evidence suggesting that misfolded proteins, accumulation of misfolded proteins, dysfunction of neuroreceptors and mitochondria, dysregulation of enzymes, and the release of neurotransmitters significantly influence the pathophysiology of these diseases. There is no effective protective medicine or therapy available even with the availability of numerous medications. There is an urgent need to create new and powerful bioactive compounds since the number of people with NDDs is rising globally. Heterocyclic compounds have consistently played a pivotal role in drug discovery due to their exceptional pharmaceutical properties. Many clinically approved drugs, such as galantamine hydrobromide, donepezil hydrochloride, memantine hydrochloride, and opicapone, feature heterocyclic cores. As these heterocyclic compounds have exceptional therapeutic potential, heterocycles are an intriguing research topic for the development of new effective therapeutic drugs for PD and AD. This review aims to provide current insights into the development and potential use of heterocyclic compounds targeting diverse therapeutic targets to manage and potentially treat patients with AD and PD.

Tetraasteranes as homologues of cubanes: effective scaffolds for drug discovery

Classical hydrocarbon scaffolds have long assisted in bringing new molecules to the market for a variety of applications, but one notable omission is that of tetraasteranes, which are homologues of cubanes belonging to a class of polycyclic hydrocarbon cage compounds. Tetraasteranes exhibit potential as scaffolds in drug discovery due to their identical cyclobutane structures and rigid conformation resembling cubanes. Based on the studies of the physical and chemical properties of tetraasteranes by density functional theory, three series of compounds were designed as homologues of cubanes by the substitution of cubane scaffolds in pharmaceuticals with tetraasteranes. Their potential for pharmaceutical applications was evaluated in silico by molecular docking and dynamics simulations. Their pharmacokinetic and physicochemical properties were studied by the ADMET (absorption, distribution, metabolism, excretion, and toxicity) analysis. The results indicate that tetraasteranes may be scaffolds as novel bioisosteres of cubanes, as well as hydrogen bond donors or acceptors, which enhance the affinity between ligands and receptors with more stable binding behavior and feasible tolerability in ADMET. All these findings provide new opportunities for tetraasteranes to serve as effective pharmaceutical scaffolds for drug discovery and to accelerate the drug discovery process by repurposing both new and old commercial compounds.

Triple-Dearomative Photocycloaddition: A Strategy to Construct Caged Molecular Frameworks

An unprecedented caged 2H-benzo-dioxo-pentacycloundecane framework was serendipitously obtained in a single transformation via triple-dearomative photocycloaddition of chromone esters with furans. This caged structure was generated as part of an effort to access a tricyclic, oxygen-bridged intermediate enroute to the dihydroxanthone natural product nidulalin A. Reaction scope and limitations were thoroughly investigated, revealing the ability to access a multitude of synthetically challenging caged scaffolds in a two-step sequence. Photophysical studies provided key mechanistic insights on the process for formation of the novel caged scaffold.

Synthetic Approach toward Diverse Oxa-Cages via Olefin Metathesis

This article demonstrates a late-stage modification of the cage propellanes that are transformed into intricate oxa-cycles via ring-rearrangement metathesis (RRM) and regioselective ring-closing metathesis (RCM) as crucial steps. In addition, we also report the extended pentacycloundecane (PCUD)-based oxa-cages involving the domino cycloetherification followed by olefin metathesis. These oxa-cages involve a domino sequence in which the PCUD core unit remains intact. [Ru]-based Grubbs catalysts are used to execute the metathesis step to assemble these higher-order oxa-cage systems. Spectroscopic data assigned structures of various products and were further supported by single-crystal X-ray diffraction analysis. The synthetic approach to these cage polycycles involves high complexity generating processes such as Diels-Alder reaction, [2 + 2] photocycloaddition, and RRM as well as RCM.

Visible-Light-Driven [2 + 2] Photocycloaddition for Constructing Dimers of N,N'-Diacyl-1,4-dihydropyrazines: Experimental and Theoretical Investigation

In this study, the visible-light-driven [2 + 2] photocycloaddition of 1,4-dihydropyrazines in solution was reported. The N,N'-diacyl-1,4-dihydropyrazines with different substituents showed completely different reactivity under the irradiation of a 430 nm blue light-emitting diode (LED) lamp. N,N'-Diacetyl-1,4-dihydropyrazine and N,N'-dipropionyl-1,4-dihydropyrazine were the only compounds capable of undergoing a [2 + 2] photocycloaddition reaction, yielding syn-dimers and cage-dimers (known as 3,6,9,12-tetraazatetraasteranes) with overall yields of 76 and 83%, correspondingly. The substituent-reactivity effect on [2 + 2] photocycloaddition of N,N'-diacyl-1,4-dihydropyrazines was investigated by density functional theory calculations. The results show that the substituents have little influence on Gibbs free energy for the [2 + 2] photocycloaddition and mainly affect the excited energy, reaction sites, and the triplet excited-state structures of 1,4-dihydropyrazines, which are closely related to whether the reaction occurs. The results offer insights into the photochemical reactivity of 1,4-dihydropyrazines and an approach for constructing dimers of N,N'-diacyl-1,4-dihydropyrazines through a solution-based visible-light-driven [2 + 2] photocycloaddition, especially for the construction of 3,6,9,12-tetraazatetraasteranes. Compared with the solid-state [2 + 2] photocycloaddition of 1,4-dihydropyrazine, this photocycloaddition will be an efficient and environmentally friendly method for synthesizing tetraazatetraasteranes with the advantages of milder reaction conditions, simple operation, adjustable reaction amounts by omitting the cocrystal growth step, etc.

Molecular Acrobatics in Polycyclic Frames: Synthesis of "Kurmanediol" via Post-synthetic Modification of Cage Molecules by Olefinic Metathesis

We report late-stage ring-opening metathesis (ROM), ring-rearrangement metathesis (RRM), and ring-closing metathesis (RCM) approaches to generate expanded pentacycloundecane (PCUD) cage derivatives. These higher-order intricate polycyclic cage systems are aesthetically pleasing and structurally intriguing. Their assembly maintains molecular symmetry during the entire synthetic sequence. To this end, metathesis-based catalysts are used to execute the ROM, RRM, and RCM strategies. The synthetic approach to these cage polycycles involves the Diels-Alder reaction, [2 + 2] photocycloaddition, RRM, ROM, and RCM as key steps.

Synthesis of Pentacycloundecane (PCUD) Based Spiro-Pyrano-Cage Framework via Ring-Closing Metathesis

Here, we demonstrate a short synthetic route to pyrano cage systems containing pentacycloundecane units by employing ring-closing metathesis (RCM) as a key step. These cage systems were constructed starting with readily available starting materials by adopting atomic economic processes such as cycloadditions (Diels-Alder reaction and [2+2] cycloaddition), Grignard addition, and olefin metathesis. The key building block, such as hexacyclic cage dione, was prepared from 1,4-naphthoquinone derivative and freshly cracked 1,3-cyclopentadiene. Some of these heterocyclic motifs are useful in biological chemistry and valuable as key synthons for high-energy-density materials.

Late-stage Modification of Cage Diones by Tandem Metathesis

Herein, we report the application of tandem ring-opening cross-metathesis (ROCM) and tandem ring-opening cross-metathesis followed by cross-metathesis (ROCM/CM) in highly strained diastereomeric heptacyclic cage diones (HCCD's) catalyzed by ruthenium catalysts. These caged diastereomeric compounds have a high degree of ring strain as well as steric congestion. Therefore, the present work related to ROCM is unique and intricate as compared to simple norbornene derivatives. It is useful to prepare new hexacyclic cage derivatives suitable for high-energy density materials. The synthetic strategy of starting cage compounds features the Diels-Alder reaction, and [2+2] photocycloaddition as key steps.

Ultrasound-assisted synthesis of kojic acid-1,2,3-triazole based dihydropyrano[3,2-b]pyran derivatives using Fe3O4@CQD@CuI as a novel nanomagnetic catalyst

The magnetic nanoparticles coated with carbon quantum dot and copper (I) iodide (Fe₃O₄@CQD@CuI) were used as eco-friendly heterogeneous Lewis / Brønsted acid sites and Cu (I) nanocatalysts. In the first step, it was applied in the synthesis of kojic acid-based dihydropyrano[3,2-b]pyran derivatives in a three-component reaction and in the second step, as a recyclable catalyst for the synthesis of kojic acid-1,2,3-triazole based dihydropyrano[3,2-b]pyran derivatives in the CuI-catalyzed azide/alkyne cycloaddition (CuAAC) reaction. The catalyst was characterized fully by using the different techniques including fourier transform infrared spectroscopy (FT-IR), elemental mapping analysis, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), X-ray spectroscopy (EDX), transmission electron microscopy (TEM), thermal gravimetric (TG) and value-stream mapping (VSM) methods. The final synthesized derivatives were identified by ¹H- and ¹³C-NMR spectroscopy.

Direct radical functionalization methods to access substituted adamantanes and diamondoids

Adamantane derivatives have diverse applications in the fields of medicinal chemistry, catalyst development and nanomaterials, owing to their unique structural, biological and stimulus-responsive properties, among others. The synthesis of substituted adamantanes and substituted higher diamondoids is frequently achieved via carbocation or radical intermediates that have unique stability and reactivity when compared to simple hydrocarbon derivatives. In this review, we discuss the wide range of radical-based functionalization reactions that directly convert diamondoid C-H bonds to C-C bonds, providing a variety of products incorporating diverse functional groups (alkenes, alkynes, arenes, carbonyl groups, etc.). Recent advances in the area of selective C-H functionalization are highlighted with an emphasis on the H-atom abstracting species and their ability to activate the particularly strong C-H bonds that are characteristic of these caged hydrocarbons, providing insights that can be applied to the C-H functionalization of other substrate classes.

Structural Insights and Docking Analysis of Adamantane-Linked 1,2,4-Triazole Derivatives as Potential 11β-HSD1 Inhibitors

The solid-state structural analysis and docking studies of three adamantane-linked 1,2,4-triazole derivatives are presented. Crystal structure analyses revealed that compound 2 crystallizes in the triclinic P-1 space group, while compounds 1 and 3 crystallize in the same monoclinic P21/c space group. Since the only difference between them is the para substitution on the aryl group, the electronic nature of these NO2 and halogen groups seems to have no influence over the formation of the solid. However, a probable correlation with the size of the groups is not discarded due to the similar intermolecular disposition between the NO2/Cl substituted molecules. Despite the similarities, CE-B3LYP energy model calculations show that pairwise interaction energies vary between them, and therefore the total packing energy is affected. HOMO-LUMO calculated energies show that the NO2 group influences the reactivity properties characterizing the molecule as soft and with the best disposition to accept electrons. Further, in silico studies predicted that the compounds might be able to inhibit the 11β-HSD1 enzyme, which is implicated in obesity and diabetes. Self- and cross-docking experiments revealed that a number of non-native 11β-HSD1 inhibitors were able to accurately dock within the 11β-HSD1 X-ray structure 4C7J. The molecular docking of the adamantane-linked 1,2,4-triazoles have similar predicted binding affinity scores compared to the 4C7J native ligand 4YQ. However, they were unable to form interactions with key active site residues. Based on these docking results, a series of potentially improved compounds were designed using computer aided drug design tools. The docking results of the new compounds showed similar predicted 11β-HSD1 binding affinity scores as well as interactions to a known potent 11β-HSD1 inhibitor.

Antimycobacterial Activity, Synergism, and Mechanism of Action Evaluation of Novel Polycyclic Amines against Mycobacterium tuberculosis

Mycobacterium tuberculosis has developed extensive resistance to numerous antimycobacterial agents used in the treatment of tuberculosis. Insufficient intracellular accumulation of active moieties allows for selective survival of mycobacteria with drug resistance mutations and accordingly promotes the development of microbial drug resistance. Discovery of compounds with new mechanisms of action and physicochemical properties that promote intracellular accumulation, or compounds that act synergistically with other antimycobacterial drugs, has the potential to reduce and prevent further drug resistance. To this end, antimycobacterial activity, mechanism of action, and synergism in combination therapy were investigated for a series of polycyclic amine derivatives. Compound selection was based on the presence of moieties with possible antimycobacterial activity, the inclusion of bulky lipophilic carriers to promote intracellular accumulation, and previously demonstrated bioactivity that potentially support inhibition of efflux pump activity. The most potent antimycobacterial demonstrated a minimum inhibitory concentration (MIC₉₉) of 9.6 μM against Mycobacterium tuberculosis H37Rv. Genotoxicity and inhibition of the cytochrome bc₁ respiratory complex were excluded as mechanisms of action for all compounds. Inhibition of cell wall synthesis was identified as a likely mechanism of action for the two most active compounds (14 and 15). Compounds 5 and 6 demonstrated synergistic activity with the known Rv1258c efflux pump substrate, spectinomycin, pointing to possible efflux pump inhibition. For this series, the nature of the side chain, rather than the type of polycyclic carrier, seems to play a determining role in the antimycobacterial activity and cytotoxicity of the compounds. Contrariwise, the nature of the polycyclic carrier, particularly the azapentacycloundecane cage, appears to promote synergistic activity. Results point to the possibility of combining an azapentacycloundecane carrier with a side chain that promotes antimycobacterial activity to develop dual acting molecules for the treatment of Mycobacterium tuberculosis.

Synthesis and biological evaluation of novel N-substituted nipecotic acid derivatives with tricyclic cage structures in the lipophilic domain as GABA uptake inhibitors

A new class of GABA reuptake inhibitors with sterically demanding, highly rigid tricyclic cage structures as the lipophilic domain was synthesized and investigated in regard to their biological activity at the murine GABA transporters (mGAT1–mGAT4). The construction of these compounds, consisting of nipecotic acid, a symmetric tricyclic amine, and a plain hydrocarbon linker connecting the two subunits via their amino nitrogens, was accomplished via reductive amination of a nipecotic acid derivative with an N-alkyl substituent displaying a terminal aldehyde function with tricyclic secondary amines. The target compounds varied with regard to spacer length, the bridge size of one of the bridges, and the substituents of the tricyclic skeleton to study the impact of these changes on their potency. Among the tested compounds nipecotic acid ethyl ester derivates with phenyl residues attached to the cage subunit showed reasonable inhibitory potency and subtype selectivity in favor of mGAT3 and mGAT4, respectively.

Decagram Synthesis of Dimethyl 1,4-Cubanedicarboxylate Using Continuous-Flow Photochemistry

The highly strained cubane system is of great interest as a scaffold and rigid linker in both pharmaceutical and materials chemistry. A straightforward approach is reported for the scale-up of a [2+2] photocycloaddition step using convenient home-made flow photoreactors to access dimethyl 1,4-cubanedicarboxylate on decagram-scale in 33–40% yield over 8 steps. The process is demonstrated on 3.4 g·h–1 input with 30 minutes residence time, enabling to reduce the process time and to avoid the use of batch photoreactors. Completion of the characterisation of the photocycloadduct and its hydrates is reported.

Memantine Derivatives as Multitarget Agents in Alzheimer's Disease

Memantine (3,5-dimethyladamantan-1-amine) is an orally active, noncompetitive N-methyl-D-aspartate receptor (NMDAR) antagonist approved for treatment of moderate-to-severe Alzheimer’s disease (AD), a neurodegenerative condition characterized by a progressive cognitive decline. Unfortunately, memantine as well as the other class of drugs licensed for AD treatment acting as acetylcholinesterase inhibitors (AChEIs), provide only symptomatic relief. Thus, the urgent need in AD drug development is for disease-modifying therapies that may require approaching targets from more than one path at once or multiple targets simultaneously. Indeed, increasing evidence suggests that the modulation of a single neurotransmitter system represents a reductive approach to face the complexity of AD. Memantine is viewed as a privileged NMDAR-directed structure, and therefore, represents the driving motif in the design of a variety of multi-target directed ligands (MTDLs). In this review, we present selected examples of small molecules recently designed as MTDLs to contrast AD, by combining in a single entity the amantadine core of memantine with the pharmacophoric features of known neuroprotectants, such as antioxidant agents, AChEIs and Aβ-aggregation inhibitors.

Substituted adamantylphthalimides: Synthesis, antiviral and antiproliferative activity

In this study, three groups of adamantylphthalimides, bearing different substituents at the phthalimide moiety, N-(4'-R² )phthalimidoadamantanes (1-7), 3-[N-(4'-R² )phthalimido]-1-adamantanols (8-10), and 3-[N-(4'-R² )phthalimido]adamantane-1-carboxylic acids (11-15), were synthesized and screened against tumor cells and viruses. The most potent compounds are not substituted at the adamantane and bear an OH or NH₂ substituent at the phthalimide (compounds 3 and 5). The antiproliferative activities of compounds 3 and 5 are in the micromolar range, much higher than the one of thalidomide. A minor antiviral activity against cytomegalovirus and varicella-zoster virus was found for compounds 3 and 5, but these compounds lacked selectivity. The results presented are important for the rational design of the next-generation compounds with anticancer and antiviral activities.

Diels–Alder reactions between cyclopentadiene analogs and benzoquinone in water and their application in the synthesis of polycyclic cage compounds

Diels–Alder reactions between cyclopentadiene analogs and p-benzoquinone were explored in water and yielded 83–97% product, higher than the results reported in water with a catalyst or cetrimonium bromide (CTAB) micelles. The novel adduct 10 was synthesized and further used to synthesize the bi-cage hydrocarbon 4,4′-spirobi[pentacyclo[5.4.0.0^2,6.0^3,10.0^5,9]undecane], which has a high density (1.2663 g cm⁻³) and a high volumetric heat of combustion (53.353 MJ L⁻¹). Four novel bi-cage hydrocarbon compounds were synthesized in water using this method starting from 2,2′-bi(p-benzoquinone) and cyclopentadiene analogs.

Diels–Alder reactions between cyclopentadiene analogs and p-benzoquinone were explored in water and yielded 83–97% product, higher than the results reported in water with a catalyst or cetrimonium bromide (CTAB) micelles.

Dyk S, Malan SF. Hexacyclododecylamines with Sigma-1 Receptor Affinity and Calcium Channel Modulating Ability

Introduction:

Recent research points to the Sigma Receptor (σR) as a possible neuromodulatory system with multi-functional action and σ1Rs have been suggested as a drug target for a number of CNS conditions. Hexacyclododecylamines have shown σ1R activity and provide an advantageous scaffold for drug design that can improve the blood-brain barrier permeability of privileged structures.

Methods and Materials:

A series of oxa- and aza- hexaxcyclododecylamines were synthesised and evaluated for sigma-1 receptor activity and voltage-gated calcium channel blocking ability to determine the effect of inclusion of amine containing heterocycles.

Results & Discussion:

The compounds had promising σ1R activities (Ki = 0.067 – 11.86 µM) with the aza-hexacyclododecylamines 12, 24 and 27 showing some of the highest affinities (Ki = 0.067 µM, 0.215 µM and 0.496 µM respectively). This confirms, as observed in previous studies, that the aza compounds are more favourable for σ1R binding than their oxa counterparts. The addition of the amine heterocycle showed affinities similar to that of related structures with only two lipophilic binding regions. This indicates that the inclusion of an amine heterocycle into these structures is a viable option in the design of new σ1R ligands. Significant voltage-gated calcium channel blocking ability was also observed for 12, 24 and 27, suggesting a link between σ1R activity and intracellular calcium levels.

Conclusion:

The σ1R activity and potential effect on other receptor classes and calcium channels could prove beneficial in pharmacological application.

Microwave Optimized Synthesis of N-(adamantan-1-yl)-4-[(adamantan-1-yl)-sulfamoyl]benzamide and Its Derivatives for Anti-Dengue Virus Activity

Dengue fever is a major public health concern in many tropical and sub-tropical regions. The development of agents that are able to inhibit the dengue virus (DENV) is therefore of utmost importance. This study focused on the synthesis of dual acting hybrids comprising structural features of known DENV inhibitors, amantadine (1) and benzsulfonamide derivatives. Hybrid compound 3, N-(adamantan-1-yl)-4-[(adamantan-1-yl)sulfamoyl]benzamide, was synthesized by reacting amantadine (1) with 4-(chlorosulfonyl)benzoic acid (2), after optimization, in a 2:1 ratio under microwave irradiation conditions in a one-pot reaction. Mono-adamantane derivatives 6 and 7 were synthesised via acyl halide formation of benzoic acid (4) and 4-sulfamoyl benzoic acid (5), respectively, followed by conjugation with amantadine (1) through a conventional or microwave irradiation assisted nucleophilic addition/substitution reaction. The use of microwave irradiation lead to significant increases in yields and a reduction in reaction times. Nuclear magnetic resonance, infra-red and mass spectral data confirmed the structures. Compound 3 and 7 showed significant anti-DENV serotype 2 activity (IC₅₀ = 22.2 µM and 42.8 µM) and low cytotoxicity (CC₅₀ < 100 µM). Possible mechanisms of action are also proposed, which are based on the biological results and molecular docking studies.

Synthesis and Biological Evaluations of NO-Donating Oxa- and Aza-Pentacycloundecane Derivatives as Potential Neuroprotective Candidates

In order to utilize the neuroprotective properties of polycyclic cage compounds, and explore the NO-donating ability of nitrophenyl groups, an array of compounds was synthesized where the different nitrophenyl groups were appended on oxa and aza-bridged cage derivatives. Biological evaluations of the compounds were done for cytotoxicity, neuroprotective abilities, the inhibition of N-methyl-d-aspartate (NMDA)-mediated Ca²⁺ influx, the inhibition of voltage-mediated Ca²⁺ influx, and S-nitrosylation abilities. All of the compounds showed low toxicity. With a few exceptions, most of the compounds displayed good neuroprotection and showed inhibitory activity for NMDA-mediated and voltage-gated calcium influx, ranging from high (>70%) to low (20–39%) inhibition. In the S-nitrosylation assay, the compounds with the nitro moiety as the NO-donating group exhibited low to good nitrosylation potency compared to the positive controls. From the biological evaluation of the tested compounds, it was not possible to obtain a simple correlation that could explain the results across all of the biological study domains. This can be ascribed to the independent processes evaluated in the different assays, which reiterate that neuroprotection is a result of multifactorial biochemical mechanisms and interactions. However, these results signify the important aspects of the pentacylcoundecylamine neuroprotectants across different biological study realms.

Synthesis and Biological Evaluation of Pentacycloundecylamines and Triquinylamines as Voltage-Gated Calcium Channel Blockers

Preclinical studies for neurodegenerative diseases have shown a multi-targeted approach to be successful in the treatment of these complex disorders with several pathoetiological pathways. Polycyclic compounds, such as NGP1-01 (7a), have demonstrated the ability to target multiple mechanisms of the complex etiology and are referred to as multifunctional compounds. These compounds have served as scaffolds with the ability to attenuate Ca(2+) overload and excitotoxicity through several pathways. In this study, our focus was on mitigating Ca(2+) overload through the L-type calcium channels (LTCC). Here, we report the synthesis and biological evaluation of several novel polycyclic compounds. We determined the IC50 values for both the pentacycloundecylamines and the triquinylamines by means of a high-throughput fluorescence calcium flux assay utilizing Fura-2/AM. The potential of these compounds to offer protection against hydrogen peroxide-induced cell death was also evaluated. Overall, 8-benzylamino-8,11-oxapentacyclo[5.4.0.0(2,6) .0(3,10) .0(5,9) ]undecane (NGP1-01, 7a) had the most favorable pharmacological profile with an IC50 value of 86 µM for LTCC inhibition and significant reduction of hydrogen peroxide-induced cell death. In general, the triquinylamines were more active as LTCC blockers than the oxa-pentacycloundecylamines. The aza-pentacycloundecylamines were potent LTCC inhibitors, with 8-hydroxy-N-phenylethyl-8,11-azapentacyclo[5.4.0.0(2,6) .0(3,10) .0(5,9) ]undecane (8b) also able to offer significant protection in the cell viability assays.

Propargylamine as functional moiety in the design of multifunctional drugs for neurodegenerative disorders: MAO inhibition and beyond

Much progress has been made in designing analogues that can potentially confer neuroprotection against debilitating neurodegenerative disorders, yet the multifactorial pathogenesis of this cluster of diseases remains a stumbling block for the successful design of an 'ultimate' drug. However, with the growing popularity of the "one drug, multiple targets" paradigm, many researchers have successfully synthesized and evaluated drug-like molecules incorporating a propargylamine function that shows potential to serve as multifunctional drugs or multitarget-directed ligands. It is the aim of this review to highlight the reported activities of these propargylamine derivatives and their prospect to serve as drug candidates for the treatment of neurodegenerative disorders.

Nanotechnology for CNS delivery of bio-therapeutic agents

The current therapeutic strategies are not efficient in treating disorders related to the central nervous system (CNS) and have only shown partial alleviation of symptoms, as opposed to, disease modifying effects. With change in population demographics, the incidence of CNS disorders, especially neurodegenerative diseases, is expected to rise dramatically. Current treatment regimens are associated with severe side-effects, especially given that most of these are chronic therapies and involve elderly population. In this review, we highlight the challenges and opportunities in delivering newer and more effective bio-therapeutic agents for the treatment of CNS disorders. Bio-therapeutics like proteins, peptides, monoclonal antibodies, growth factors, and nucleic acids are thought to have a profound effect on halting the progression of neurodegenerative disorders and also provide a unique function of restoring damaged cells. We provide a review of the nano-sized formulation-based drug delivery systems and alternate modes of delivery, like the intranasal route, to carry bio-therapeutics effectively to the brain.