Browsing by Author "Joubert, Jacques"
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Item Antimycobacterial Activity, Synergism, and Mechanism of Action Evaluation of Novel Polycyclic Amines against Mycobacterium tuberculosis(Advances in Pharmacological and Pharmaceutical Sciences, 2021-06) Kapp, Erika; Joubert, Jacques; Sampson, Samantha, L; Malan, Sarel, F; Sharma, Rajan; Warner, Digby, F; Seldon, Ronnett; Jordaan, Audrey; de Vos, MargarethaMycobacterium 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.Item Common defciencies found in generic Finished Pharmaceutical Product (FPP) applications submitted for registration to the South African Health Products Regulatory Authority (SAHPRA)(Springer Nature, 2022) Moeti, Lerato; Litedu, Madira; Joubert, JacquesThe aim of the study was to investigate the common defciencies observed in the Finished Pharmaceutical Product (FPP) section of generic product applications submitted to SAHPRA. The study was conducted retrospectively over a 7-year period (2011–2017) for products that were fnalised by the Pharmaceutical and Analytical pre-registration Unit.There were 3148 fnalised products in 2011–2017, 667 of which were sterile while 2089 were non-sterile. In order to attain a representative sample for the study, statistical sampling was conducted. Sample size was obtained using the statistical tables found in literature and confrmed by a sample size calculation with a 95% confdence level. The selection of the products was according to the therapeutic category using the multi-stage sampling method called stratifed-systematic sampling. This resulted in the selection of 325 applications for non-sterile products and 244 applications for sterile products. Subsequently, all the defciencies were collected and categorised according to Common Technical Document (CTD) subsections of the FPP section (3.2.P).Item Common Deficiencies Found in the Active Pharmaceutical Ingredient (API) Section of Non-sterile Generic Products Submitted for Registration by SAHPRA(Springer Science and Business Media Deutschland GmbH, 2023) Moeti, Lerato; Joubert, JacquesPurpose: This research study aims to determine the qualitative and quantitative common deficiencies included in the API section of dossiers submitted to SAHPRA. The study was conducted retrospectively over a 7-year period (2011–2017) for non-sterile generic products that were finalised by the Pharmaceutical and Analytical pre-registration Unit. In this period, the restricted part of the CTD was evaluated when needed therefore this was not conducted on all applications. The requirement to evaluate the restricted part for all applications was initiated in January 2020, thus, a separate study has been conducted to identify the common deficiencies in the restricted part. Methods: There were 2089 applications finalised between 2011 and 2017 and in order to attain a representative sample for the study, the multi-stage statistical sampling called the ‘stratified systematic sampling’ was selected as the method of choice. Sample size was obtained using the statistical tables found in the literature and confirmed by a sample size calculation with a 95% confidence level, resulting in the selection of 325 applications. Subsequently, all the deficiencies were collected and categorised according to CTD subsections. For the restricted part study, all new applications evaluated between January to May 2020 were used. Results: A total of 1130 deficiencies were collected from 325 applications sampled. The majority of the identified deficiencies were from Module 3.2.S.3.1 (19.38%) on characterisation, Module 3.2.S.1.3 (19.11%) on general properties, Module 3.2.S.4.1 (10.44%) on specifications and Module 3.2.S.4.3 (8.32%) on validation of analytical methods. The study on the restricted parts included the five most common deficiencies that SAHPRA has identified, which are similar to those observed from the 2011–2017 applications. This confirms that the quality of the evaluations has been maintained over the years. Comparison of the deficiencies with those reported by other agencies such as the USFDA, EMA, WHOPQTm and TFDA are discussed with similarities clearly outlined. Conclusions: The most common deficiencies observed by SAHPRA were extensively discussed. These findings could serve as a guidance for API manufacturers to submit better quality APIMFs which will improve turnaround times for registration and accelerate access to medicines for patients. © 2021, The Drug Information Association, Inc.Item Crystal structure, Hirshfeld surface analysis and DFT studies of 5-(adamantan-1-yl)-3-[(4- chlorobenzyl)sulfanyl]-4-methyl4H-1,2,4-triazole, a potential 11βHSD1 inhibitor(Scientific Reports, 2019) Joubert, Jacques; Al-Wahaibi, Lamya; Blacque, Olivier5-(Adamantan-1-yl)-3-[(4-chlorobenzyl)sulfanyl]-4-methyl-4H-1,2,4-triazole (4) was identifed as a potential 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) inhibitor and this paper describes the in-depth structural analysis thereof. Compound 4 was synthesized in a 92% yield and its 3D-structure confrmed by single-crystal X-ray difraction. Hirshfeld surface analysis indicated that H…H, C-H…C, C-H…Cl and especially C-H…N hydrogen bond interactions are the primary contributors to the intermolecular stabilisation in the crystal. In order to explore the properties of 4, free from the infuence of the crystal feld, density functional theory (DFT) calculations were conducted. Results indicated that the DFT optimized geometry of 4 produced a conformer (4a) that is signifcantly diferent from the crystal structure. Further experiments confrmed that the crystal structure is not the absolute minimum conformation. This indicated that the crystal packing forces has signifcantly infuenced the conformation thereof. Frontier molecular orbital energies and net atomic charges were also calculated to elucidate the electronic properties of 4a. These results provided insight into areas of the molecule that may present with the ability to form binding interactions at the 11β-HSD1 active site. Molecular docking experiments revealed important intermolecular interactions between 4a and 11β-HSD1. These results indicate that 4 may be considered for further drug design endeavors.Item Crystal structure, hirshfeld surface analysis and dft studies of 5-(adamantan-1-yl)-3-[(4-chlorobenzyl)sulfanyl]-4-methyl-4h-1,2,4-triazole, a potential 11β-hsd1 inhibitor(Scientific Reports, 2019) Joubert, Jacques5-(Adamantan-1-yl)-3-[(4-chlorobenzyl)sulfanyl]-4-methyl-4H-1,2,4-triazole (4) was identified as a potential 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) inhibitor and this paper describes the in-depth structural analysis thereof. Compound 4 was synthesized in a 92% yield and its 3D-structure confirmed by single-crystal X-ray diffraction.Item Discovery of 9-phenylacridinediones as highly selective butyrylcholinesterase inhibitors through structure-based virtual screening(Elsevier, 2020) Joubert, Jacques; Kapp, ErikaButyrylcholinesterase (BuChE) is considered a promising drug target as it plays an important role in the pro-gression of late stage Alzheimer’s disease (AD). Two compound libraries were selected and 64 124 aminecontaining moieties were screened using a hierarchical virtual screening protocol to discover new selectiveBuChE inhibitors. From these and subsequent docking experiments, 9-phenylacridinedione (9-PAD) was iden-tified as a promising scaffold for selective inhibition of BuChE. Selected top dock scored 9-PADs were assayedand compounds3and6exhibited potent and highly selective human BuChE inhibition (IC50: 98 nM and 142 nM,respectively). Both molecules were also predicted to show sufficient brain permeability, not have any substantialtoxicities, especially hepatotoxicity, and no significantinvitrocytotoxicity against SH-SY5Y neuroblastoma cellsat concentrations up to 100 μM. These findings indicate that 9-PAD is a promising lead structure for the de-velopment of agents able to treat late stage AD.Item The implementation of a risk based assessment approach by the South African Health pProducts Regulatory Authority (SAHPRA)(Springer, 2023) Moeti, Lerato; Litedu, Madira; Joubert, JacquesAn extensive backlog of pending regulatory decisions is one of the major historical challenges that the South African Health Products Regulatory Authority (SAHPRA) inherited from the Medicine Control Council (MCC). Revising and implementing new regulatory pathways is one of the strategic mechanisms that SAHPRA employs to circumvent this problem. To alleviate the backlog, the use of a new review pathway termed the risk-based review on the scientifc quality and bioequivalence assessments was explored. The objective of the study was to articulate the risk-based assessment (RBA) pathway, to determine robust criteria for the classifcation of the levels of risk for medicines, and to defne the improved process to be followed in the assessment and approval of medicines.Item Investigation of common deficiencies observed in scientific assessments and the implementation of a new robust review pathway, the risk-based assessment approach, by the South African Health Regulatory Authority, SAHPRA(University of the Western Cape, 2022) Moeti, Lerato Petunia; Joubert, JacquesThe main objective of this study is to improve patient access to medicines. The research is two-fold, the first component promotes transparency between the South African Health Products Regulatory Authority (SAHPRA), pharmaceutical companies, manufacturers and clinical research organisations by investigating deficiencies in scientific assessments of medicines submitted for approval. The common deficiencies from the regional, Active Pharmaceutical Ingredient (API), Finished Pharmaceutical Product (FPP) and Bioequivalence study sections of dossiers submitted to SAHPRA were qualitatively and quantitatively investigated. The investigation was conducted retrospectively between 2011 to 2017 for non-sterile and sterile generic products finalised by the P&A pre-registration Unit. To strengthen the conclusions, up-to-date data was also collected between 2020-2021 to confirm the consistency of the findings.Item Microwave-assisted methods for the synthesis of pentacyclo[5.4.0.02,6.03,10.05,9]undecylamines(Elsevier, 2013) Joubert, Jacques; Sharma, Rajan; Onani, Martin O.; Malan, Sarel F.Efficient methodologies for the preparation of pentacyclo[5..4.0.02,6.03,10.05,9]undecane (PCU) amine derivatives are described via microwave-assisted synthesis. The obtained results revealed that microwave-assisted synthetic procedures under controlled conditions (power, temperature and time) are very convenient, high yielding, efficient and low-cost methods for the preparation of PCU amine derivatives. The new methods show several advantages including operational simplicity, good performance, significant reduction in reaction time, less by-product formation and easier purification.Item Multi-targeted directed ligands for Alzheimer’s disease: design of novel lead coumarin conjugates(Taylor & Francis, 2018) Repsold, B.P.; Malan, Sarel F.; Joubert, Jacques; Oliver, D.W.Alzheimer’s Disease (AD) is a neurodegenerative disease characterized by central nervous system insults with progressive cognitive (memory, attention) and non-cognitive (anxiety, depression) impairments. Pathophysiological events affect predominantly cholinergic neuronal loss and dysfunctions of the dopaminergic system. The aim of the current study was to design multi-targeted directed lead structures based on the coumarin scaffold with inhibitory properties at two key enzymes in disease relevant systems, i.e. acetylcholinesterase (AChE) and monoamine oxidase B (MAO-B). Conventional and microwave synthetic methods were utilized to synthesize coumarin scaffoldbased novel morpholino, piperidino, thiophene and erucic acid conjugates. Biological assays indicated that the coumarin–morpholine ether conjugate BPR 10 was the most potent hMAO-B inhibitor. The coumarin–piperidine conjugates BPR 13 and BPR 12 were the most potent inhibitors of eeAChE at 100 μM and 1 μM, respectively. Molecular modelling studies were conducted with Accelrys® Discovery Studio® V3.1.1 utilising the published hMAO-B (2V61) and hAChE (4EY7) crystal structures. Compound BPR 10 occupies both the entrance and substrate cavities of the active site of MAO-B. BPR 13 resides in both the peripheral anionic site (PAS) and the catalytic anionic site (CAS) of hAChE. This study demonstrated that the coumarin scaffold serves as a promising pharmacophore for MTDLs design.Item Novel norbornane derivatives as potential neuroprotective agents(University of Western Cape, 2020) Egunlusi, Ayodeji Olatunde; Joubert, Jacques; Malan, SarelNeurodegenerative disorders are characterised by progressive loss of the brain’s physiological functions as a result of gradual degeneration of neurons in the central nervous system. Even though they are classified as diseases of the elderly, occurrence earlier in life is possible, but that would suggest the influence of genetic and/or environmental factors. Due to the continuous rise in modernisation and industrialisation over the years, there has been an increase in incidence and prevalence of neurodegenerative disorders. With the advances in technology and life expectancy, the rates of the common forms (Alzheimer’s disease and Parkinson’s disease), are expected to increase exponentially by 2050. Unfortunately, there is still no clinically approved treatment or therapy to slow down or halt the degenerative process as most registered drugs only offer symptomatic relief. Confounding this issue is the lack of definite mechanism of neurodegeneration, which is still poorly defined and not completely understood. Nonetheless, the pathology of most neurodegenerative disorders is believed to be a combination of interrelated processes that eventually leads to neuronal cell death. Among the postulated processes, the impact of excitotoxicity mediated by NMDA receptor over-activation is prominent and it is implicated in virtually all neurodegenerative disorders. With this basic insight, it is believed that molecules capable of inhibiting NMDA receptors and associated calcium channels, without affecting the normal physiological functions of the brain, could potentially serve as good neuroprotective drugs. Competitive and uncompetitive blockers (MK-801 and ketamine) have been explored, but none were clinically accepted due to undesirable side effects such as hallucinations, sedation and depression. However, NGP1-01, a polycyclic cage molecule, has been shown to be neuroprotective through modulation of NMDA receptors and voltage gated calcium channels and attenuation of MPP+ -induced toxicity. A similar approach could be useful in the design and development of new neuroprotective drugs. The aim of this study was to synthesise a series of open and rearranged cage-like molecules and explore their neuroprotective potential in neuroblastoma SH-SY5Y cells. The proposed structures, with norbornane scaffolds that contained different moieties, were designed to structurally resemble NGP1-01 and MK-801. Once synthesised, the compounds were purified and characterised, and were evaluated for their biological activities. Compounds were first screened for cytotoxicity at different concentrations. Thereafter, they were evaluated for neuroprotective effects against MPP+ -induced excitotoxicity and for calcium flux modulatory effects on NMDA receptor and voltage gated calcium channels. The norbornane derivatives were synthesised and characterised, and all final products were afforded in sufficient yields. All compounds with the exception of two compounds displayed good cytotoxic profiles towards the SH-SY5Y neuroblastoma cells at 10 µM, 50 µM and 100 µM concentrations as they demonstrated percentage cell viabilities close to 100% (control treated cells). Only two compounds showed percentage cell viability of 51% and 59% at 100 µM. Utilising the same cell line, all compounds, tested at 10 µM, attenuated MPP+ -induced toxicity after 24 hours of exposure to a neurotoxin. This was evident in the 23% to 53% enhancement (significant with p < 0.05) in cell viability when compared to the MPP+ only treated cells. In comparison to known NMDA receptor and/or voltage gated calcium channel blockers (MK-801, NGP1-01 or nimodipine), the synthesised compounds demonstrated mono or dual inhibition of calcium channels as they effectively attenuated calcium influx by blocking NMDA receptors and/or voltage gated calcium channels expressed in neuroblastoma SHSY5Y cells. This group of compounds were found to be more potent NMDA receptor inhibitors, probably due to similarities with MK-801 and memantine, than voltage gated calcium channel inhibitors. All compounds demonstrated moderate to good calcium inhibitory effects at NMDA receptors in the range of 23% to 70% while a selected few displayed very little or no activity at the voltage gated calcium channels. In conclusion, 27 compounds with norbornane scaffolds were successfully synthesised and evaluated for cytotoxicity and neuroprotection. The abilities of the synthesised compounds to protect neurons from the neurotoxin MPP+ and reduce calcium flux into neuronal cells were successfully demonstrated. These characteristics are essential in neuroprotection as they may prove significant in halting or slowing down the disease progression. The compounds showing a good cytotoxicity profile, neuroprotective effects and ability to reduce calcium overload, could potentially act as neuroprotective agents with good safety profiles or contribute as lead structures to the development and design of structurally related molecules that could clinically benefit people with neurodegenerative disorders.Item Novel tricycloundecane derivatives as potential N-methyl-Daspartate receptor and calcium channel inhibitors for neuroprotection(University of the Western Cape, 2014) Egunlusi, Ayodeji Olatunde; Joubert, Jacques; Malan, SarelThis study focused on the synthesis of a series of novel tricycloundecane derivatives and evaluation of these compounds for neuroprotection using the fluorescent ratiometric calcium assay that indicates the ability of the test compounds to inhibit NMDA receptors and VGCC. The cycloaddition reaction between p-benzoquinone and monomerised dicyclopentadiene yielded tricycloundeca- 4,9-diene-3,6-dione which was used as the base structure and further derivatised. These derivatives were conjugated with benzylamine to form a series of imines and amines. A total of 10 compounds were synthesised for evaluation of inhibition of calcium influx through NMDA receptor channels and voltage-gated calcium channels. The structures were confirmed using NMR, IR and MS. On the proton NMR, the characteristic AB-quartet system was observed in the region of 1-2 ppm for all the compounds and the aromatic moiety was observed between 6.5-7.5 ppm for the novel polycyclic amines. These, with other functional groups, were used to confirm the individual structuresItem Polycyclic compounds as carriers for neuroactive non- steroidal anti-inflammatory drugs(University of the Western Cape, 2017) Abaniwonda, Modupe; Joubert, JacquesRecent scientific findings have highlighted the beneficial roles of polycyclic cage compounds in neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. Further interest into the chemistry of these compounds is stimulated by their remarkable ability to improve the pharmacokinetics profile of known neuroprotective agents. As potent lipophilic scaffolds, they can be employed to target the brain delivery of desired compounds. Inflammation is a key mediator of neuronal cell's degeneration as activated microglia and other inflammatory mediators propagate oxidative damage and neuronal loss. Epidemiological and clinical evidence suggests that non-steroidal anti-inflammatory drugs (NSAIDs) slow down the progression and onset of neurodegenerative diseases. The beneficial effects of NSAIDs in ND can be attributed to their ability to inhibit cyclooxygenase enzymes thereby halting the biosynthesis of prostaglandins (PG) which are powerful mediators of inflammation. NSAIDs also inhibit the expression of pro- inflammatory genes. Despite their potential neuroprotective activity, NSAIDs are poorly lipophilic due to the presence of polar carboxylic acid groups and will therefore ionise at physiological pH, deterring them from reaching the desired site of action in the central nervous system (CNS).Item Polycyclic propargylamine derivatives as multifunctional neuroprotective agents(University of the Western Cape, 2018) Zindo, Frank T.; Joubert, Jacques; F. Malan, SarelThe abnormal death of neurons in the central nervous system of individuals suffering from neurodegenerative diseases such as Parkinson’s disease, Alzheimer’s disease, Huntington’s disease and amyotrophic lateral sclerosis, takes place by an intrinsic cell suicide programme known as apoptosis. This process is triggered by several stimuli, and consists of numerous pathways and cascades which lead to the death of neuronal cells. It is this multifactorial nature of neurodegenerative diseases that has over the years seen many researchers develop compounds that may serve as multi-target directed ligands (MTDLs) which could potentially confer neuroprotection by acting simultaneously on different receptors and target sites implicated in neurodegeneration. This study was aimed at developing MTDLs that may serve as neuroprotective agents by simultaneously (a) inhibiting N-methyl D-aspartate receptors (NMDAR) and blocking L-type voltage gated calcium channels (VGCC) thus regulating the Ca2+ influx mediated excitotoxic process; (b) inhibiting the monoamine oxidase enzymes A and -B (MAO-A/B) thus allowing increase in dopamine levels in the central nervous system and reducing the levels of the highly oxidative products produced by the activity of these enzymes; (c) possessing anti-apoptotic activity to halt the neuronal cell death process. In designing the compounds we focused on the structures of rasagiline and selegiline, two well-known MAO-B inhibitors and proposed neuroprotective agents, and of NGP1-01, a known VGCC blocker and NMDAR antagonist. The first series of compounds (reported in research article 1, Chapter 3), comprised polycyclic propargylamine and acetylene derivatives. Compounds 12, 15 and 16 from this series showed promising VGCC and NMDA receptor channel inhibitory activity ranging from 18 % to 59 % in micromolar concentrations, and compared favourably to the reference compounds. In the MAO-B assay, compound 10 exhibited weak MAO-B inhibition of 73.32 % at 300 μM. The rest of the series showed little to no activity on these target sites, despite showing significant anti-apoptotic activity. This suggested the compounds in this series to be exhibiting their neuroprotective action through some other mechanism(s) unexplored in this study.Item Regulatory registration timelines of generic medicines in South Africa: Assessment of the performance of SAHPRA between 2011 and 2022(Springer, 2023) Moeti, Lerato; Litedu, Madira; Joubert, JacquesVarious regulatory authorities are experiencing backlogs of applications which result in delayed access to medicines for patients. The objective of this study is to critically assess the registration process utilised by SAHPRA between 2011 and 2022 and determine the fundamental root causes for the formation of a backlog. The study also aims to detail the remedial actions that were undertaken which resulted in the development of a new review pathway termed the risk-based assessment approach for regulatory authorities experiencing backlogs to implement. A sample of 325 applications was used to evaluate the end-to-end registration process employed for the Medicine Control Council (MCC) process between 2011 and 2017; 129 applications were used for the backlog clearance project (BCP) between 2019 and 2022; 63 and 156 applications were used for the risk-based assessment (RBA) pilot studies in 2021 and 2022, respectively. The three processes are compared, and the timelines are discussed in detail.Item Small molecule efflux pump inhibitors in Mycobacterium tuberculosis: a rational drug design perspective(Bentham Science Publishers, 2018) Kapp, Erika; Malan, Sarel F.; Joubert, Jacques; Sampson, Samantha L.Drug resistance in Mycobacterium tuberculosis (M. tuberculosis) complicates management of tuberculosis. Efflux pumps contribute to low level resistance and acquisition of additional high level resistance mutations through sub-therapeutic concentrations of intracellular antimycobacterials. Various efflux pump inhibitors (EPIs) have been described for M. tuberculosis but little is known regarding the mechanism of efflux inhibition. As knowledge relating to the mechanism of action and drug target is central to the rational drug design of safe and sufficiently selective EPIs, this review aims to examine recent developments in the study of EPIs in M. tuberculosis from a rational drug development perspective and to provide an overview to facilitate systematic development of therapeutically effective EPIs. Review of literature points to a reduction in cellular energy or direct binding to the efflux pump as likely mechanisms for most EPIs described for M. tuberculosis. This review demonstrates that, where a direct interaction with efflux pumps is expected, both molecular structure and general physicochemical properties should be considered to accurately predict efflux pump substrates and inhibitors. Non-competitive EPIs do not necessarily demonstrate the same requirements as competitive inhibitors and it is therefore essential to differentiate between competitive and non-competitive inhibition to accurately determine structure activity relationships for efflux pump inhibition. It is also evident that there are various similarities between inhibitors of prokaryotic and eukaryotic efflux pumps but, depending on the specific chemical scaffolds under investigation, it may be possible to design EPIs that are less prone to inhibition of human P-glycoprotein, thereby reducing side effects and drug-drug interactions.Item Structural analysis, molecular modelling and preliminary competition bnding studies of AM-DAN as a NMDA Receptor PCP-Site Fluorescent Ligand(MDPI, 2019) Ndzibongwana, Sethu; Ngobese, Samukelo; Sayed, Ahmad; Shongwe, Ciniso; White-Phillips, Simon; Joubert, JacquesExcitotoxicity related to the dysfunction of the N-methyl-d-aspartate receptor (NMDAR) has been indicated to play an integral role in the pathophysiology of multiple disease states, including neurodegenerative disorders such as Parkinson’s disease. There is a notable gap in the market for novel NMDAR antagonists, however current methods to analyse potential antagonists rely on indirect measurements of calcium flux and hazardous radioligand binding assays. Recently, a fluorescent NMDAR ligand, N-adamantan-1-yl-dimethylamino-1-naphthalenesulfonic acid, known as AM-DAN was developed by our group. Additional studies on this ligand is necessary to evaluate its potential as a biological tool in NMDAR research. Therefore, this study was aimed at conducting structural analyses, fluorescence experiments, high-accuracy NMDAR molecular modelling and NMDAR phencyclidine (PCP) site competition binding studies using AM-DAN. Results revealed that AM-DAN has appropriate structural properties, significant fluorescent ability in various solvents and is able to bind selectively and compete for the PCP-binding site of the NMDAR. Therefore, AM-DAN holds promise as a novel fluorescent ligand to measure the affinity of prospective drugs binding at the NMDAR PCP-site and may circumvent the use of radioligands.Item Structural Insights and Docking Analysis of Adamantane-Linked 1,2,4-Triazole Derivatives as Potential 11 -HSD1 Inhibitors(Molecules, 2021) Osman, Doaa, A; Macias, Mario, A; Zondagh, Luke, S; Joubert, Jacques; Al- Wahaibi, Lamya, H; Al- Shaalan, Nora, H; Garcia- Granda, Santiago; El-Emam, Ali, AThe 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 11 -HSD1 enzyme, which is implicated in obesity and diabetes. Self- and cross-docking experiments revealed that a number of non-native 11 -HSD1 inhibitors were able to accurately dock within the 11 -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 11 -HSD1 binding affinity scores as well as interactions to a known potent 11 -HSD1 inhibitor.Item A supramolecular derivatised study of BIS(Adamantan-1- Aminium) carbonate(University of the Western Cape, 2014) Ngilirabanga, Jean Baptiste; Samsodien, Halima; Joubert, JacquesIn this study, new solid supramolecular derivatised forms of bis(adamantine-1-aminium) carbonate (ADTCO3) were prepared. ADTCO3 is a derivative of amantadine used for Parkinson’s disease and has antiviral properties against influenza-A, dengue fever and pharmacological activity towards Parkinson’s disease. The new forms prepared were polymorphic and co-crystal forms of ADTCO3. Polymorphism is a phenomenon where the ability of a substance to exist in two or more crystalline forms occurs when crystallised under different conditions and co-crystallization is the process of formation of multicomponent crystals of a drug substance. New solid forms often display different mechanical, physicochemical and thermal properties that can remarkably influence the bioavailability, hygroscopicity and stability of active pharmaceutical ingredients (APIs). For the formation of polymorphs of ADTCO3, techniques such as dry grinding, solvent-drop grinding, co-precipitation, sublimation and vapour diffusion were applied. For the development of co-crystals and/or complex formation, ADTCO3 was treated in combination with ten selected co-formers viz; benzoic acid, 4-hydroxybenzoic acid, cinnamic acid, 4-hydroxycinnamic acid, succinic acid, tartaric acid, salicylic acid, L-glutamic acid, citric acid monohydrate and L-glutaric acid using similar techniques as applied in the polymorphism study. The first four co-formers were selected for their potential biological activity and the latter six were selected for their generally regarded as safe (GRAS) status. All products were isolated and characterized using different analytical techniques to assess the thermal behaviour of the products by hot stage microscopy (HSM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). FTIR spectroscopy and proton-nuclear magnetic resonance (1HNMR) were used to identify and determine the purity of the parent compounds and the modified forms. X-ray powder diffraction was used to determine the formation of a new phase and single crystal X-ray diffraction was applied at the initial stages to identify ADTCO3 by its unit cell parameters. Furthermore, the Cambridge Structural Database (CSD) and other resources were used to generate information on the molecular structures of all elucidated parent compounds, their polymorphs and reported co-crystals. Four different polymorphic forms of ADTCO3 were identified (viz. ADTCO3 Forms I to IV) and sixteen co-crystals (viz. ADTCO3BA1 to ADTCO3BA5, ADTCO3HBA, ADTCO3CIN, ADTCO3HCIN, ADTCO3SUC, ADTCO3LTTA, ADTCO3SA, ADTCO3CA, ADTCO3GLA, ADTCO3GA) were synthesised. Of the sixteen co-crystals 5 were identified as ADTCO3BA “salt” co-crystal polymorphic forms and 2 as ADTCO3SUC co-crystal polymorphic forms. Two solvated “salt” co-crystal forms were also identified, namely; ADTCO3GLA and ADTCO3LTTA. ADTCO3GLA had a mass loss of 10.3% (n = 2.4) and ADTCO3LTTA had a mass loss of 5.25% (n = 0.86). Finally, the rest of the co-crystals ADTCO3HBA, ADTCO3CIN, ADTCO3HCIN, ADTCO3SA, ADTCO3CA and ADTCO3GA all crystallised as “salt” co-crystals.Item Synthesis & biological evaluation of neuroprotective molecules with polycyclic scaffolds(University of the Western Cape, 2017) Sharma, Rajan; Malan, Sarel F.; Joubert, JacquesAmong neurological disorders, many of the most devastating disorders are neurodegenerative. Modern research associates excitotoxicity to a variety of neuropathological conditions, suggesting that the neurodegenerative diseases with distinct etiologies may have excitotoxicity as a common pathway. Excitotoxicity occurs through over-stimulation of receptors for excitatory neurotransmitters like the N-methyl-D-aspartate (NMDA) receptors. Due to the relevance of NMDA receptors and excitotoxic processes, the antagonism or modulation of NMDA receptors is used as a therapeutic tool against neurodegenerative diseases. NMDA receptor activity can be modulated by S-nitrosylation and this modulation of NMDA receptor activity can be utilised in the development of neuroprotective drugs.