171 results on '"Tricia Naicker"'
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2. The need to merge supercritical fluid chromatography into undergraduate curricula for the twenty-first century
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Tricia Naicker and Kamini Govender
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green chemistry ,supercritical fluid chromatography ,pharmacy/chemistry undergraduate curricula ,pharmaceutical chemistry ,Science ,Chemistry ,QD1-999 - Abstract
Complementarity to liquid and gas chromatography, supercritical fluid chromatography (SFC) is becoming a mainstream separation technique. There is a global demand for more SFC users since ‘green’ method development has become a favorable target for research into sustainable technologies. In order to parallel this trend, there is a need to incorporate SFC into the relevant curricula to provide students with this pertinent chromatographic separation knowledge. There is currently limited SFC training in undergraduate modules compared to traditional liquid/gas chromatography and mass spectrometry. Herein, we comment on the evolution of SFC, and the move to this greener chemistry technology with increased industrial applications, to highlight the importance of including this technique in future undergraduate modules.
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- 2021
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3. Neutralizing Carbapenem Resistance by Co-Administering Meropenem with Novel β-Lactam-Metallo-β-Lactamase Inhibitors
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Nakita Reddy, Letisha Girdhari, Mbongeni Shungube, Arnoldus C. Gouws, Byron K. Peters, Kamal K. Rajbongshi, Sooraj Baijnath, Sipho Mdanda, Thandokuhle Ntombela, Thilona Arumugam, Linda A. Bester, Sanil D. Singh, Anil Chuturgoon, Per I. Arvidsson, Glenn E. M Maguire, Hendrik G. Kruger, Thavendran Govender, and Tricia Naicker
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metallo-β-lactamases ,Carbapenem resistant Enterobacterales ,cyclic amino acidic chelator ,BP2 ,murine thigh infection model ,Therapeutics. Pharmacology ,RM1-950 - Abstract
Virulent Enterobacterale strains expressing serine and metallo-β-lactamases (MBL) genes have emerged responsible for conferring resistance to hard-to-treat infectious diseases. One strategy that exists is to develop β-lactamase inhibitors to counter this resistance. Currently, serine β-lactamase inhibitors (SBLIs) are in therapeutic use. However, an urgent global need for clinical metallo-β-lactamase inhibitors (MBLIs) has become dire. To address this problem, this study evaluated BP2, a novel beta-lactam-derived β-lactamase inhibitor, co-administered with meropenem. According to the antimicrobial susceptibility results, BP2 potentiates the synergistic activity of meropenem to a minimum inhibitory concentration (MIC) of ≤1 mg/L. In addition, BP2 is bactericidal over 24 h and safe to administer at the selected concentrations. Enzyme inhibition kinetics showed that BP2 had an apparent inhibitory constant (Kiapp) of 35.3 µM and 30.9 µM against New Delhi Metallo-β-lactamase (NDM-1) and Verona Integron-encoded Metallo-β-lactamase (VIM-2), respectively. BP2 did not interact with glyoxylase II enzyme up to 500 µM, indicating specific (MBL) binding. In a murine infection model, BP2 co-administered with meropenem was efficacious, observed by the >3 log10 reduction in K. pneumoniae NDM cfu/thigh. Given the promising pre-clinical results, BP2 is a suitable candidate for further research and development as an (MBLI).
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- 2023
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4. Special Issue: Advances in the Synthesis of Biologically Important Intermediates/Drugs
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Tricia Naicker
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n/a ,Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Biology (General) ,QH301-705.5 ,Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
Chemical synthesis is a cornerstone of the development of medicinal chemistry, forming the basis for discovering compounds with new physical and/or biological properties [...]
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- 2023
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5. Mass Spectrometric Imaging of the Brain Demonstrates the Regional Displacement of 6‑Monoacetylmorphine by Naloxone
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Belin G. Teklezgi, Annapurna Pamreddy, Sphamandla Ntshangase, Sipho Mdanda, Sanil D. Singh, Nirmala D. Gopal, Tricia Naicker, Hendrik G. Kruger, Thavendran Govender, and Sooraj Baijnath
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Chemistry ,QD1-999 - Published
- 2020
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6. A novel and more efficient biosynthesis approach for human insulin production in Escherichia coli (E. coli)
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Kamini Govender, Tricia Naicker, Johnson Lin, Sooraj Baijnath, Anil Amichund Chuturgoon, Naeem Sheik Abdul, Taskeen Docrat, Hendrik Gerhardus Kruger, and Thavendran Govender
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Biosynthesis of human insulin ,Diabetes ,E. coli ,Biotechnology ,TP248.13-248.65 ,Microbiology ,QR1-502 - Abstract
Abstract Insulin has captured researchers’ attention worldwide. There is a rapid global rise in the number of diabetic patients, which increases the demand for insulin. Current methods of insulin production are expensive and time-consuming. A PCR-based strategy was employed for the cloning and verification of human insulin. The human insulin protein was then overexpressed in E. coli on a laboratory scale. Thereafter, optimisation of human insulin expression was conducted. The yield of human insulin produced was approximately 520.92 (mg/L), located in the intracellular fraction. Human insulin was detected using the MALDI-TOF-MS and LC–MS methods. The crude biosynthesised protein sequence was verified using protein sequencing, which had a 100% similarity to the human insulin sequence. The biological activity of human insulin was tested in vitro using a MTT assay, which revealed that the crude biosynthesised human insulin displayed a similar degree of efficacy to the standard human insulin. This study eliminated the use of affinity tags since an untagged pET21b expression vector was employed. Tedious protein renaturation, inclusion body recovery steps, and the expensive enzymatic cleavage of the C-peptide of insulin were eliminated, thereby making this method of biosynthesising human insulin a novel and more efficient method.
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- 2020
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7. Improved Synthesis and Isolation of Bedaquiline
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Hlengekile Lubanyana, Per I. Arvidsson, Thavendran Govender, Hendrik G. Kruger, and Tricia Naicker
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Chemistry ,QD1-999 - Published
- 2020
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8. Mass Spectrometry Imaging Demonstrates the Regional Brain Distribution Patterns of Three First-Line Antiretroviral Drugs
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Sphamandla Ntshangase, Sipho Mdanda, Sanil D. Singh, Tricia Naicker, Hendrik G. Kruger, Sooraj Baijnath, and Thavendran Govender
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Chemistry ,QD1-999 - Published
- 2019
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9. Alterations in neurotransmitter levels and transcription factor expression following intranasal buprenorphine administration
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Sanelisiwe P. Xhakaza, Leon J. Khoza, Advaitaa M. Haripershad, Terisha Ghazi, Shanel Dhani, Cosmas Mutsimhu, Molopa J. Molopa, Nithia P. Madurai, Lorna Madurai, Sanil D. Singh, Nirmala D. Gopal, Hendrik G. Kruger, Thavendran Govender, Anil Chuturgoon, Tricia Naicker, and Sooraj Baijnath
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Buprenorphine ,Opioid addiction ,Brain-derived neurotrophic factor (BDNF) ,Cyclic AMP response element-binding protein (CREB) ,Neurotransmitters ,Therapeutics. Pharmacology ,RM1-950 - Abstract
Buprenorphine is an opioid drug used in the management of pain and the treatment opioid addiction. Like other opioids, it is believed that it achieves these effects by altering functional neurotransmitter pathways and the expression of important transcription factors; cyclic AMP response element-binding protein (CREB) and brain-derived neurotrophic factor (BDNF) in the brain. However, there is a lack of scientific evidence to support these theories. This study investigated the pharmacodynamic effects of BUP administration by assessing neurotransmitter and molecular changes in the healthy rodent brain. Sprague-Dawley rats (150–200 g) were intranasally administered buprenorphine (0.3 mg/mL) and sacrificed at different time points: 0.25, 0.5, 1, 2, 4, 6, 8 and 24 h post drug administration. LC-MS was used to quantify BUP and neurotransmitters (GABA, GLUT, DA, NE and 5-HT) in the brain, while CREB and BDNF gene expression was determined using qPCR. Results showed that BUP reached a Cmax of 1.21 ± 0.0523 ng/mL after 2 h, with all neurotransmitters showing an increase in their concentration over time, with GABA, GLUT and NE reaching their maximum concentration after 8 h. DA and 5-HT reached their maximum concentrations at 1 h and 24 h, respectively post drug administration. Treatment with BUP resulted in significant upregulation in BDNF expression throughout the treatment period while CREB showed patterns of significant upregulation at 2 and 8 h, and downregulation at 1 and 6 h. This study contributes to the understanding of the pharmacodynamic effects of BUP in opioid addiction by proving that the drug significantly influences NT pathways that are implicated in opioid addiction.
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- 2021
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10. Kinetic and thermodynamic characterisation of HIV-protease inhibitors against E35D↑G↑S mutant in the South African HIV-1 subtype C protease
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Sibusiso Maseko, Eden Padayachee, Siyabonga Maphumulo, Thavendran Govender, Yasien Sayed, Glenn Maguire, Johnson Lin, Tricia Naicker, Sooraj Baijnath, and Kruger Hendrik Gerhardus
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protease ,hiv ,mutant ,inhibitor ,thermodynamics ,Therapeutics. Pharmacology ,RM1-950 - Abstract
Herein, we report the effect of nine FDA approved protease inhibitor drugs against a new HIV-1 subtype C mutant protease, E35D↑G↑S. The mutant has five mutations, E35D, two insertions, position 36 (G and S), and D60E. Kinetics, inhibition constants, vitality, Gibbs free binding energies are reported. The variant showed a decreased affinity for substrate and low catalytic efficiency compared to the wild type. There was a significant decrease in the binding of seven FDA approved protease inhibitors against the mutant (p
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- 2019
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11. Stereoselective synthesis towards unnatural proline based amino acids
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Sifiso S.Makhathini, Sukant K. Das, Thishana Singh, Per I. Arvidsson, Hendrik G. Kruger, Hendra Gunosewoyo, Thavendran Govender, and Tricia Naicker
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Organic chemistry ,QD241-441 - Published
- 2016
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12. Correction to 'Improved Synthesis and Isolation of Bedaquiline'
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Hlengekile Lubanyana, Per I. Arvidsson, Thavendran Govender, Hendrik G. Kruger, and Tricia Naicker
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Chemistry ,QD1-999 - Published
- 2020
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13. (S)-Benzyl 3-phenylcarbamoyl-1,2,3,4-tetrahydroisoquinoline-2-carboxylate
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Glenn E. M. Maguire, Hendrick G. Kruger, Madichaba Chelopo, Thavendran Govender, and Tricia Naicker
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Crystallography ,QD901-999 - Abstract
There are two independent molecules in the asymmetric unit of the title compound, C24H22N2O3. The heterocyclic ring assumes a twisted boat conformation and N—H...O interactions help to construct the three-dimensional network within the crystal packing.
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- 2012
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14. (S)-Methyl 2-benzamido-3-(3,4-dimethoxyphenyl)propanoate
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Tricia Naicker, Thavendran Govender, Hendrick. G. Kruger, and Glenn E. M. Maguire
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Crystallography ,QD901-999 - Abstract
The dimethoxypbenzene ring in the title compound, C19H21NO5, is gauche to the amide group and anti to the ester group. The chirality was confirmed to be S from two-dimensional NMR spectroscopy. In the crystal, N—H...O and C—H...O hydrogen bonds and several short-contact interactions (2.07–3.45 Å) create chains parallel to [110]. The phenyl ring is disordered over two orientations in a 0.54 (2):0.46 (2) ratio.
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- 2012
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15. (1R,3S)-N-Benzhydryl-2-benzyl-6,7-dimethoxy-1-phenyl-1,2,3,4-tetrahydroisoquinoline-3-carbothioamide
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Tricia Naicker, Thavendran Govender, Hendrick. G. Kruger, and Glenn E. M. Maguire
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Crystallography ,QD901-999 - Abstract
The title compound, C38H36N2O2S, has a heterocyclic ring that assumes a half-chair conformation. The phenyl rings of neighbouring molecules align forming alternating chains parallel to [100] within the crystal packing. The absolute stereochemistry of the crystal was confirmed to be R,S at the 1- and 3-positions, respectively, by proton NMR spectroscopy. A single intramolecular N—H...N hydrogen bond is observed.
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- 2011
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16. (S)-Methyl 3-(3,4-dimethoxyphenyl)-2-[2-(diphenylphosphanyl)benzamido]propanoate
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Tricia Naicker, Thavendran Govender, Hendrick G. Kruger, and Glenn E. M. Maguire
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Crystallography ,QD901-999 - Abstract
Molecules of the title compound, C31H30NO5P, show a sttagered conformation about the C—C bond joining the dimethoxybenzene group to the chiral centre, with the dimethoxybenzene ring gauche to the amide group and anti to the ester group. In the crystal, weak intermolecular N—H...O and C—H...O hydrogen bonds form layers parallel to (110).
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- 2011
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17. (1S,3S)-Methyl 2-benzyl-6,7-dimethoxy-1-phenyl-1,2,3,4-tetrahydroisoquinoline-3-carboxylate
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Tricia Naicker, Thavendran Govender, Hendrik. G. Kruger, and Glenn. E. M. Maguire
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Crystallography ,QD901-999 - Abstract
In the title compound, C26H27NO4, the heterocyclic ring assumes a half-chair conformation and intermolecular C—H...O interactions help to construct the three-dimensional network within the crystal packing.
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- 2011
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18. 6,7-Dimethoxy-3-methoxycarbonyl-1-(2-methoxyphenyl)-3,4-dihydroisoquinoline 2-oxide
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Tricia Naicker, Thavendran Govender, Hendrik G. Kruger, and Glenn E. M. Maguire
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Crystallography ,QD901-999 - Abstract
In the title compound, C20H21NO6, an N-oxide-based organocatalyst, the N-containing six-membered ring adopts a twisted half-chair conformation. No hydrogen bonding or π–π stacking was found within the crystal structure.
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- 2011
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19. (1S,3S)-Methyl 6,7-dimethoxy-1-phenyl-1,2,3,4-tetrahydroisoquinoline-3-carboxylate
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Tricia Naicker, Thavendran Govender, Hendrik G. Kruger, and Glenn E. M. Maguire
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Crystallography ,QD901-999 - Abstract
In the title compound, C19H21NO4, an organocatalyst with a tetrahydroisoquinoline backbone, the heterocyclic ring assumes a half-boat conformation. The dihedral angle between the aromatic rings is 82.93 (8)°. In the crystal, molecules are linked via N—H...O and C—H...O hydrogen bonds, forming a layer parallel to (10-1).
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- 2011
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20. (S)-2-Benzyl-N-(2,6-diisopropylphenyl)-1,2,3,4-tetrahydroisoquinoline-3-carboxamide
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Tricia Naicker, Thavendran Govender, Hendrik G. Kruger, and Glenn E. M. Maguire
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Crystallography ,QD901-999 - Abstract
The asymmetric unit of the title compound, C29H34N2O, contains two molecules in which the N-containing six-membered rings assume different conformations viz. half-chair and envelope. Intermolecular N—H...O hydrogen bonding via the amide groups cross-link the molecules in the crystal structure.
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- 2011
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21. Methyl 1-cyclohexyl-6,7-dimethoxy-3,4-dihydroisoquinoline-3-carboxylate
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Tricia Naicker, Thavendran Govender, Hendrik. G Kruger, and Glenn. E. M Maguire
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Crystallography ,QD901-999 - Abstract
There are two independent molecules in the asymmetric unit of the title compound, C19H25NO4. A single C—H...π interaction and various intermolecular contacts (2.65–2.83 Å) link the independent molecules in the crystal structure. The N-containing six-membered ring assumes a twisted half-boat conformation.
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- 2011
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22. Benzyl 5-hydroxy-4-oxapentacyclo[5.4.1.02,6.03,10.08,11]dodecane-3-carboxylate
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Rajshekhar Karpoormath, Tricia Naicker, Thavendran Govender, Hendrik G. Kruger, and Glenn E. M. Maguire
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Crystallography ,QD901-999 - Abstract
The title compound, C19H18O4, exhibits a long C—C bond [1.575 (2) Å] in the cage structure. In the crystal, pairs of O—H...O hydrogen bonds link the molecules into centrosymmetric dimers. C—H...O interactions also occur.
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- 2011
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23. (3S)-2-Benzyl-3-carboxy-1,2,3,4-tetrahydroisoquinolinium chloride monohydrate
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Glenn E. M. Maguire, Hendrik G. Kruger, Thavendran Govender, and Tricia Naicker
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Crystallography ,QD901-999 - Abstract
In the title compound, C17H18NO2+·Cl−·H2O, a precursor to novel asymmetric catalysts, the N-containing six-membered ring of the tetrahydroquinolinium unit assumes a half-boat conformation. In the crystal, intermolecular O—H...O, O—H...Cl, N—H...Cl and C—H...O hydrogen bonds and C—H...π interactions link the molecules into a three-dimensional network.
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- 2011
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24. (S)-N-Benzyl-2-methyl-1,2,3,4-tetrahydroisoquinoline-3-carboxamide
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Glenn. E.M. Maguire, Hendrik. G. Kruger, Thavendran Govender, and Tricia Naicker
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Crystallography ,QD901-999 - Abstract
The structure of the title compound, C18H20N2O, at 173 K has hexagonal (P61) symmetry. The N-containing six-membered ring assumes a half-chair conformation. In the crystal, intermolecular N—H...O hydrogen bonding via the amide groups cross-link the molecules along the a axis. The absolute configuration was confirmed by 2D NMR studies.
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- 2011
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25. (1R,3S)-Methyl 6,7-dimethoxy-1-(4-methoxyphenyl)-1,2,3,4-tetrahydroisoquinoline-3-carboxylate
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Glenn E. M. Maguire, Hendrik G. Kruger, Thavendran Govender, and Tricia Naicker
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Crystallography ,QD901-999 - Abstract
The title compound, C20H23NO5, is the third in a series of tetrahydoisoquinoline (TIQ) compounds that are precursors to novel chiral catalysts. The N-containing six-membered ring assumes a half-boat conformation. No hydrogen bonding is observed in the crystal structure.
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- 2010
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26. {(1R,3S)-2-Benzyl-6,7-dimethoxy-1-phenyl-1,2,3,4-tetrahydroisoquinolin-3-yl}diphenylmethanol
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Glenn E.M. Maguire, Hendrik G. Kruger, Thavendran Govender, and Tricia Naicker
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Crystallography ,QD901-999 - Abstract
In the title compound, C37H35NO3, a precursor to novel chiral catalysts, the N-containing six-membered ring assumes a half-chair conformation. Intermolecular C—H...O hydrogen bonds link the molecules in the crystal structure.
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- 2010
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27. (1R,3S)-Methyl 2-benzyl-6,7-dimethoxy-1-phenyl-1,2,3,4-tetrahydroisoquinoline-3-carboxylate
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Glenn E. M. Maguire, Hendrik G. Kruger, Thavendran Govender, Michael McKay, and Tricia Naicker
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Crystallography ,QD901-999 - Abstract
In the title compound, C26H27NO4, a precursor to novel chiral catalysts, the N-containing six-membered ring assumes a half-boat conformation. Various C—H...π interactions and intermolecular short contacts (C...H = 2.81–2.90 Å) link the molecules together in the crystal structure.
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- 2009
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28. In Vitro and In Vivo Development of a β-Lactam-Metallo-β-Lactamase Inhibitor: Targeting Carbapenem-Resistant Enterobacterales
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Byron K. Peters, Nakita Reddy, Mbongeni Shungube, Letisha Girdhari, Sooraj Baijnath, Sipho Mdanda, Lloyd Chetty, Thandokuhle Ntombela, Thilona Arumugam, Linda A. Bester, Sanil D. Singh, Anil Chuturgoon, Per I. Arvidsson, Glenn E. M. Maguire, Hendrik G. Kruger, Tricia Naicker, and Thavendran Govender
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Infectious Diseases - Published
- 2023
29. Computational insights for predicting the binding and selectivity of peptidomimetic plasmepsin IV inhibitors against cathepsin D
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Lucas Sousa Martins, Hendrik Gerhardus Kruger, Tricia Naicker, Cláudio Nahum Alves, Jerônimo Lameira, and José Rogério Araújo Silva
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General Chemical Engineering ,General Chemistry - Abstract
Free energy calculations explain the selectivity of peptidomimetic inhibitors to PlmIV and CatD enzymes. Insights for the development of novel potent and selective PlmIV inhibitors are provided.
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- 2023
30. Organic Base-Mediated Carboxylation of (Hetero)aromatic Compounds Using Supercritical Carbon Dioxide (scCO2)
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Tricia Naicker, Hendrik Gerhardus Kruger, Lloyd Christopher Chetty, Per I Arvidsson, and Thavendran Govender
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Organic Chemistry ,Catalysis - Abstract
A straightforward site-selective method for the direct carboxylation of resorcinols (3-hydroxyphenol derivatives), phenols, and indoles is reported. The products were obtained in moderate to high yields using supercritical carbon dioxide as an electrophile and solvent under basic conditions. This method offers solvent and metal free conditions without the cumbersome exclusion of air or water with convenient purification.
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- 2022
31. The in vitro and in vivo potential of metal-chelating agents as metallo-beta-lactamase inhibitors against carbapenem-resistant Enterobacterales
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Kehinde F Omolabi, Nakita Reddy, Sipho Mdanda, Sphamandla Ntshangase, Sanil D Singh, Hendrik G Kruger, Tricia Naicker, Thavendran Govender, and Sooraj Bajinath
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Genetics ,Molecular Biology ,Microbiology - Abstract
The recent surge in beta-lactamase resistance has created superbugs, which pose a current and significant threat to public healthcare. This has created an urgent need to keep pace with the discovery of inhibitors that can inactivate these beta-lactamase producers. In this study, the in vitro and in vivo activity of 1,4,7-triazacyclononane-1,4,7 triacetic acid (NOTA)—a potential metallo-beta-lactamase (MBL) inhibitor was evaluated in combination with meropenem against MBL producing bacteria. Time–kill studies showed that NOTA restored the efficacy of meropenem against all bacterial strains tested. A murine infection model was then used to study the in vivo pharmacokinetics and efficacy of this metal chelator. The coadministration of NOTA and meropenem (100 mg/kg.bw each) resulted in a significant decrease in the colony-forming units of Klebsiella pneumoniae NDM-1 over an 8-h treatment period (>3 log10 units). The findings suggest that chelators, such as NOTA, hold strong potential for use as a MBL inhibitor in treating carbapenem-resistant Enterobacterale infections.
- Published
- 2022
32. Antibiotic‐Derived Radiotracers for Positron Emission Tomography: Nuclear or 'Unclear' Infection Imaging?
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Arno Christiaan Gouws, Hendrik Gerhardus Kruger, Olivier Gheysens, Jan Rijn Zeevaart, Thavendran Govender, Tricia Naicker, and Thomas Ebenhan
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Positron-Emission Tomography ,General Chemistry ,General Medicine ,Radiopharmaceuticals ,Catalysis ,Anti-Bacterial Agents - Abstract
The excellent features of non-invasive molecular imaging, its progressive technology (real-time, whole-body imaging and quantification), and global impact by a growing infrastructure for positron emission tomography (PET) scanners are encouraging prospects to investigate new concepts, which could transform clinical care of complex infectious diseases. Researchers are aiming towards the extension beyond the routinely available radiopharmaceuticals and are looking for more effective tools that interact directly with causative pathogens. We reviewed and critically evaluated (challenges or pitfalls) antibiotic-derived PET radiopharmaceutical development efforts aimed at infection imaging. We considered both radiotracer development for infection imaging and radio-antibiotic PET imaging supplementing other tools for pharmacologic drug characterization; overall, a total of 20 original PET radiotracers derived from eleven approved antibiotics.
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- 2022
33. Using Antibiotics Scaffolds Will Warrant Novel Radiotracers for Effective Positron Emission Tomography Imaging of Infections: Triumph or Pitfall?
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Arno Christiaan Gouws, Hendrik Gerhardus Kruger, Mike Machaba Sathekge, Jan Rijn Zeevaart, Thavendran Govender, Tricia Naicker, and Thomas Ebenhan
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- 2022
34. Mechanistic insight on the inhibition of D, D-carboxypeptidase from Mycobacterium tuberculosis by β-lactam antibiotics: an ONIOM acylation study
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Sibusiso B. Maseko, Gyanu Lamichhane, Bahareh Honarparvar, Tricia Naicker, Thavendran Govender, Thandokuhle Ntombela, Glenn E. M. Maguire, Anya Seupersad, Collins U. Ibeji, Gideon F. Tolufashe, Sooraj Baijnath, Hendrik G. Kruger, and Siyabonga I. Maphumulo
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ONIOM ,chemistry.chemical_classification ,0303 health sciences ,biology ,030303 biophysics ,General Medicine ,biology.organism_classification ,Carboxypeptidase ,Cell wall ,Acylation ,Mycobacterium tuberculosis ,03 medical and health sciences ,chemistry.chemical_compound ,Enzyme ,Biochemistry ,chemistry ,Structural Biology ,biology.protein ,Lactam ,Peptidoglycan ,Molecular Biology - Abstract
Mycobacterium tuberculosis cell wall is intricate and impermeable to many agents. A D, D-carboxypeptidase (DacB1) is one of the enzymes involved in the biosynthesis of cell wall peptidoglycan and catalyzes the terminal D-alanine cleavage from pentapeptide precursors. Catalytic activity and mechanism by which DacB1 functions is poorly understood. Herein, we investigated the acylation mechanism of DacB1 by β-lactams using a 6-membered ring transition state model that involves a catalytic water molecule in the reaction pathway. The full transition states (TS) optimization plus frequency were achieved using the ONIOM (B3LYP/6-31 + G(d): AMBER) method. Subsequently, the activation free energies were computed via single-point calculations on fully optimized structures using B3LYP/6-311++(d,p): AMBER and M06-2X/6-311++(d,p): AMBER with an electronic embedding scheme. The 6-membered ring transition state is an effective model to examine the inactivation of DacB1 via acylation by β-lactams antibiotics (imipenem, meropenem, and faropenem) in the presence of the catalytic water. The ΔG# values obtained suggest that the nucleophilic attack on the carbonyl carbon is the rate-limiting step with 13.62, 19.60 and 30.29 kcal mol−1 for Imi–DacB1, Mero–DacB1 and Faro–DacB1, respectively. The electrostatic potential (ESP) and natural bond orbital (NBO) analysis provided significant electronic details of the electron-rich region and charge delocalization, respectively, based on the concerted 6-membered ring transition state. The stabilization energies of charge transfer within the catalytic reaction pathway concurred with the obtained activation free energies. The outcomes of this study provide important molecular insight into the inactivation of D, D-carboxypeptidase by β-lactams. Communicated by Ramaswamy H. Sarma
- Published
- 2021
35. A 2018–2019 patent review of metallo beta-lactamase inhibitors
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Nakita Reddy, Sooraj Baijnath, Tricia Naicker, Mbongeni Shungube, Hendrik G. Kruger, Thavendran Govender, and Per I. Arvidsson
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Pharmacology ,Bacteria ,biology ,Drug Synergism ,General Medicine ,Carbapenem-resistant enterobacteriaceae ,beta-Lactams ,biology.organism_classification ,beta-Lactam Resistance ,Anti-Bacterial Agents ,Microbiology ,Patents as Topic ,Antibiotic resistance ,Drug Development ,Drug Discovery ,Animals ,Humans ,beta-Lactamase Inhibitors ,Beta-Lactamase Inhibitors - Abstract
Antibiotic resistance caused by beta-lactamase expressing bacteria poses a concern given its global dissemination and proliferation. The emergence of the metallo beta-lactamases is an indefinite health threat toward which current antibiotics have limited clinical efficacy. One solution is to develop metallo beta-lactamase inhibitors (MBLIs) capable of restoring the activity of beta-lactam drugs.This review focuses on potential metallo beta-lactamase inhibitors that have been patented during the period of 2018-2019. The aim is to provide insight into the diverse class of compounds which exhibit a synergistic inhibitory effect on carbapenem-resistant bacteria, when co-administered with a beta-lactam antibiotic.The treatment strategy, of creating a broad-spectrum beta-lactamase inhibitor, is beneficial to the health sector as well as rural communities. Unfortunately, most of the inhibitors lack published data from both
- Published
- 2020
36. Mass Spectrometric Imaging of the Brain Demonstrates the Regional Displacement of 6‑Monoacetylmorphine by Naloxone
- Author
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Nirmala Gopal, Sooraj Baijnath, Thavendran Govender, Sipho Mdanda, Sphamandla Ntshangase, Belin G. Teklezgi, Hendrik G. Kruger, Annapurna Pamreddy, Sanil D. Singh, and Tricia Naicker
- Subjects
medicine.drug_class ,business.industry ,Narcotic ,General Chemical Engineering ,medicine.medical_treatment ,Antagonist ,General Chemistry ,(+)-Naloxone ,Pharmacology ,Receptor antagonist ,Article ,chemistry.chemical_compound ,Chemistry ,Globus pallidus ,Opioid ,chemistry ,medicine ,6-Monoacetylmorphine ,business ,NLX ,QD1-999 ,medicine.drug - Abstract
Overdose is the main cause of mortality among heroin users. Many of these overdose-induced deaths can be prevented through the timely administration of naloxone (NLX), a nonselective mu (μ)-, kappa (κ)-, and delta (δ)-opioid receptor antagonist. NLX competitively inhibits opioid-overdose-induced respiratory depression without eliciting any narcotic effect itself. The aim of this study was to investigate the antagonistic action of NLX by comparing its distribution to that of 6-monacetylmorphine (6-MAM), heroin's major metabolite, in a rodent model using mass spectrometric imaging (MSI) in combination with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Male Sprague-Dawley rats (n = 5) received heroin (10 mg kg-1) intraperitoneally, NLX (10 mg kg-1) intranasally, and NLX injected intranasally 5 min after heroin administration. The animals were sacrificed 15 min after dose and brain tissues were harvested. The MSI image analysis showed a region-specific distribution of 6-MAM in the brain regions including the corpus callosum, hippocampal formation, cerebral cortex, corticospinal tracts, caudate putamen, thalamus, globus pallidus, hypothalamus, and basal forebrain regions of the brain. The antagonist had a similar biodistribution throughout the brain in both groups of animals that received NLX or NLX after heroin administration. The MSI analysis demonstrated that the intensity of 6-MAM in these brain regions was reduced following NLX treatment. The decrease in 6-MAM intensity was caused by its displacement by the antagonist and its binding to these receptors in these specific brain regions, consequently enhancing the opioid elimination. These findings will contribute to the evaluation of other narcotic antagonists that might be considered for use in the treatment of drug overdose via MSI.
- Published
- 2020
37. Improved Synthesis and Isolation of Bedaquiline
- Author
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Per I. Arvidsson, Thavendran Govender, Hlengekile Lubanyana, Tricia Naicker, and Hendrik G. Kruger
- Subjects
Lithium amide ,Chemistry ,General Chemical Engineering ,Diastereomer ,Enantioselective synthesis ,Sparteine ,General Chemistry ,Combinatorial chemistry ,Article ,chemistry.chemical_compound ,Supercritical fluid chromatography ,medicine ,Amine gas treating ,Bedaquiline ,Enantiomer ,QD1-999 ,medicine.drug - Abstract
Bedaquiline (BDQ) is the most critical pharmaceutical in the world for treating multidrug-resistant Mycobacterium tuberculosis. Despite it being highly effective, BDQ asymmetric synthesis remains a challenge. Herein, the influence of chiral bases, namely, bis(1-phenylethyl)amine, bisoxazoline, and sparteine on the diastereoselective lithiation reaction to obtain BDQ was investigated. The highest diastereoselective ratio (dr) emerged as 90:10 from the (+)-bis[(R)-1-phenylethyl] lithium amide. This is a significant improvement from the 50:50 dr achieved from the commercial synthesis. Thereafter, the desired (90:10 RS, SR) diastereomeric mixture was easily isolated via a gravity column and subjected to chiral supercritical fluid chromatography (SFC) to access the desired enantiomer (1R, 2S)-BDQ. The advantages of this procedure are enhanced diastereoselection as well as a greener, faster way to achieve excellent enantioseparation (up to 1.0 g scale).
- Published
- 2020
38. Microwave-Accelerated N-Acylation of Sulfoximines with Aldehydes under Catalyst-Free Conditions
- Author
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Kamal K. Rajbongshi, Tricia Naicker, Thavendran Govender, Hendrik G. Kruger, Per I. Arvidsson, and Srinivas Ambala
- Subjects
010405 organic chemistry ,Chemistry ,Organic Chemistry ,010402 general chemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Acylation ,chemistry.chemical_compound ,N acylation ,Microwave irradiation ,Radical initiator ,Organic chemistry ,N-Bromosuccinimide ,Microwave - Abstract
An efficient catalyst-free radical cross-coupling reaction between aromatic aldehydes and sulfoximines was developed. The reaction took place in the presence of N-bromosuccinimide as the radical initiator under microwave irradiation to afford the corresponding acylated sulfoximines in moderate to excellent yields (27 examples). This protocol proved to be rapid, easy to handle, and applicable to a broad scope of substrates.
- Published
- 2020
39. Microwave-assisted synthesis of meso-carboxyalkyl-BODIPYs and an application to fluorescence imaging
- Author
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Glenn E. M. Maguire, Hendrick G. Kruger, Neliswa Z Mhlongo, Thavendran Govender, Tricia Naicker, Thomas Ebenhan, and Cathryn H.S. Driver
- Subjects
chemistry.chemical_classification ,Fluorescence-lifetime imaging microscopy ,Chemistry ,Carboxylic acid ,Organic Chemistry ,Peptide ,Ligand (biochemistry) ,Biochemistry ,Fluorescence ,Combinatorial chemistry ,Autofluorescence ,In vivo ,Physical and Theoretical Chemistry ,Ex vivo - Abstract
In this study, a significantly improved method for the synthesis of modular meso-BODIPY (boron dipyrromethene) derivatives possessing a free carboxylic acid group (which was subsequently coupled to peptides), is disclosed. This method provides a vastly efficient synthetic route with a > threefold higher overall yield than other reports. The resultant meso-BODIPY acid allowed for further easy incorporation into peptides. The meso-BODIPY peptides showed absorption maxima from 495–498 nm and emission maxima from 504–506 nm, molar absorptivity coefficients from 33 383–80 434 M−1 cm−1 and fluorescent quantum yields from 0.508–0.849. The meso-BODIPY-c(RGDyK) peptide was evaluated for plasma stability and (proved to be durable even up to 4 h) was then assessed for its fluorescence imaging applicability in vivo and ex vivo. The optical imaging in vivo was limited due to autofluorescence, however, the ex vivo tissue analysis displayed BODIPY-c(RGDyK) internalization and cancer detection thereby making it a novel tumor-integrin associated fluorescent probe while displaying the lack of interference the dye has on the properties of this ligand to bind the receptor.
- Published
- 2020
40. Mass Spectrometry Imaging Demonstrates the Regional Brain Distribution Patterns of Three First-Line Antiretroviral Drugs
- Author
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Hendrik G. Kruger, Sanil D. Singh, Thavendran Govender, Sipho Mdanda, Tricia Naicker, Sooraj Baijnath, and Sphamandla Ntshangase
- Subjects
Drug ,Efavirenz ,business.industry ,General Chemical Engineering ,media_common.quotation_subject ,Central nervous system ,virus diseases ,General Chemistry ,Pharmacology ,Corpus callosum ,Emtricitabine ,Article ,Mass spectrometry imaging ,Chemistry ,chemistry.chemical_compound ,medicine.anatomical_structure ,chemistry ,Pharmacokinetics ,Distribution (pharmacology) ,Medicine ,business ,QD1-999 ,medicine.drug ,media_common - Abstract
HIV in the central nervous system (CNS) contributes to the development of HIV-associated neurological disorders (HAND), even with chronic antiretroviral therapy. In order for antiretroviral therapy to be effective in protecting the CNS, these drugs should have the ability to localize in brain areas known to be affected by HIV. Consequently, this study aimed to investigate the localization patterns of three first-line antiretroviral drugs, namely, efavirenz, tenofovir, and emtricitabine, in the rat brain. Liquid chromatography–tandem mass spectrometry (LC–MS/MS) and matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) were utilized to assess the pharmacokinetics and brain spatial distribution of the three drugs. Each drug was administered (50 mg/kg) to healthy female Sprague–Dawley rats via intraperitoneal administration. LC–MS/MS results showed that all three drugs could be delivered into the brain, although they varied in blood–brain barrier permeability. MALDI-MSI showed a high degree of efavirenz localization across the entire brain, while tenofovir localized mainly in the cortex. Emtricitabine distributed heterogeneously mainly in the thalamus, corpus callosum, and hypothalamus. This study showed that efavirenz, tenofovir, and emtricitabine might be a potential drug combination antiretroviral therapy for CNS protection against HAND.
- Published
- 2019
41. Spatial distribution of elvitegravir and tenofovir in rat brain tissue: Application of matrix‐assisted laser desorption/ionization mass spectrometry imaging and liquid chromatography/tandem mass spectrometry
- Author
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Thavendran Govender, Hendrik G. Kruger, Tricia Naicker, Sphamandla Ntshangase, Sooraj Baijnath, and Sipho Mdanda
- Subjects
Cmax ,Neuroimaging ,Quinolones ,Mass spectrometry ,Tandem mass spectrometry ,01 natural sciences ,Mass spectrometry imaging ,Analytical Chemistry ,Rats, Sprague-Dawley ,Tandem Mass Spectrometry ,Liquid chromatography–mass spectrometry ,medicine ,Animals ,Tissue Distribution ,Tenofovir ,Spectroscopy ,Brain Chemistry ,Chromatography ,Chemistry ,Elvitegravir ,010401 analytical chemistry ,Organic Chemistry ,Brain ,Rats ,0104 chemical sciences ,Matrix-assisted laser desorption/ionization ,Anti-Retroviral Agents ,Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization ,Drug delivery ,Female ,Chromatography, Liquid ,medicine.drug - Abstract
Rationale The complexity of central nervous system (CNS) drug delivery is the main obstacle with the blood-brain barrier (BBB) known to restrict access of most pharmaceutical drugs into the brain. Mass spectrometry imaging (MSI) offers possibilities for studying drug deposition into the CNS. Methods The deposition and spatial distribution of the two antiretroviral drugs elvitegravir and tenofovir in the brain were investigated in healthy female Sprague-Dawley rats following a single intraperitoneal administration (50 mg/kg). This was achieved by the utilization of quantitative liquid chromatography/tandem mass spectrometry (LC/MS/MS) and matrix-assisted laser desorption/ionization (MALDI) MSI. Results LC/MS/MS showed that elvitegravir has better BBB penetration, reaching maximum concentration in the brain (Cmax brain) of 976.5 ng/g. In contrast, tenofovir displayed relatively lower BBB penetration, reaching Cmax brain of 54.5 ng/g. MALDI-MSI showed the heterogeneous distribution of both drugs in various brain regions including the cerebral cortex. Conclusions LC/MS/MS and MALDI-MSI provided valuable information about the relative concentration and the spatial distribution of the two common antiretroviral drugs. This study has also shown the capability of MALDI-MSI for direct visualization of pharmaceutical drugs in situ.
- Published
- 2019
42. Zidovudine and Lamivudine as Potential Agents to Combat HIV-Associated Neurocognitive Disorder
- Author
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Thavendran Govender, Sanil D. Singh, Sooraj Baijnath, Tricia Naicker, Hendrik G. Kruger, Sipho Mdanda, and Sphamandla Ntshangase
- Subjects
Oncology ,medicine.medical_specialty ,Anti-HIV Agents ,Central nervous system ,Neurocognitive Disorders ,Human immunodeficiency virus (HIV) ,HIV Infections ,medicine.disease_cause ,HIV-associated neurocognitive disorder ,030226 pharmacology & pharmacy ,Rats, Sprague-Dawley ,03 medical and health sciences ,Zidovudine ,0302 clinical medicine ,Pharmacokinetics ,Tandem Mass Spectrometry ,Internal medicine ,Drug Discovery ,Lc ms ms ,medicine ,Animals ,Tissue Distribution ,030304 developmental biology ,0303 health sciences ,business.industry ,virus diseases ,Lamivudine ,medicine.disease ,Rats ,medicine.anatomical_structure ,Molecular Medicine ,Female ,Complication ,business ,Injections, Intraperitoneal ,Chromatography, Liquid ,medicine.drug - Abstract
The central nervous system has been identified as an anatomical reservoir for HIV due the difficulties in delivering therapeutic agents into the brain and this complication results in HIV-...
- Published
- 2019
43. Brain penetration of ketamine: Intranasal delivery VS parenteral routes of administraion
- Author
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Sphamandla Ntshangase, Thavendran Govender, Sipho Mdanda, Vivian Naidoo, Tricia Naicker, Hendrik G. Kruger, Sooraj Baijnath, and Panjasaram Naidoo
- Subjects
Male ,Administration, Oral ,Pharmacology ,Rats, Sprague-Dawley ,03 medical and health sciences ,Route of administration ,0302 clinical medicine ,Pharmacokinetics ,medicine ,Animals ,Infusions, Parenteral ,Ketamine ,Administration, Intranasal ,Biological Psychiatry ,business.industry ,Brain ,medicine.disease ,Symptomatic relief ,Antidepressive Agents ,Rats ,030227 psychiatry ,Psychiatry and Mental health ,Anesthetic ,Antidepressant ,Nasal administration ,business ,Treatment-resistant depression ,030217 neurology & neurosurgery ,Chromatography, Liquid ,medicine.drug - Abstract
Ketamine is approved by the FDA to be used as an anesthetic however, recent reports have exhibited its success in the treatment of major depressive disorder (MDD). Studies have suggested that a sub-anesthetic dose produces rapid antidepressant activity providing significant symptomatic relief particularly in patients with a history of treatment resistant depression (TRD). Many reports have been published on the intranasal (IN) efficacy of ketamine in the treatment of depression, however studies that have investigated the effects of the route of administration on drug delivery to the brain appear to be absent in literature. Therefore, in this study, a single dose (15 mg/kg body weight) was administered via different routes of administration [oral (PO), intranasal (IN) and intraperitoneal (IP)] to healthy male Sprague-Dawley rats in order to determine the brain tissue pharmacokinetics of ketamine. A novel validated liquid chromatography-mass spectrometry (LC-MS) method was developed using a fused core column for the determination of ketamine in plasma and brain homogenates. While IP administration resulted in favorable concentrations in the brain and plasma; IN administration, which is supposed to favour drug delivery to the brain, exhibited moderately low drug levels post administration. PO administration produced significantly lower levels due to extensive first-pass metabolism in the liver and intestines. These results have implications for future studies exploring the use of ketamine for the treatment of MDD in order to optimize treatment regimens and suggest that parenteral administration of ketamine should be used in the treatment of depression.
- Published
- 2019
44. The Driving Force for the Acylation of β ‐Lactam Antibiotics by L,D‐Transpeptidase 2: Quantum Mechanics/Molecular Mechanics (QM/MM) Study
- Author
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Monsurat M. Lawal, Gyanu Lamichhane, Thavendran Govender, Hendrik G. Kruger, Glenn E. M. Maguire, Gideon F. Tolufashe, Collins U. Ibeji, Bahareh Honarparvar, and Tricia Naicker
- Subjects
Models, Molecular ,Isodesmic reaction ,Molecular Structure ,Stereochemistry ,Bond strength ,Acylation ,beta-Lactams ,Atomic and Molecular Physics, and Optics ,Transition state ,Anti-Bacterial Agents ,Ring strain ,QM/MM ,chemistry.chemical_compound ,Models, Chemical ,chemistry ,Amide ,Peptidyl Transferases ,Lactam ,Quantum Theory ,Peptide bond ,Computer Simulation ,Physical and Theoretical Chemistry - Abstract
β-lactam antibiotics, which are used to treat infectious diseases, are currently the most widely used class of antibiotics. This study focused on the chemical reactivity of five- and six-membered ring systems attached to the β-lactam ring. The ring strain energy (RSE), force constant (FC) of amide (C-N), acylation transition states and second-order perturbation stabilization energies of 13 basic structural units of β-lactam derivatives were computed using the M06-2X and G3/B3LYP multistep method. In the ring strain calculations, an isodesmic reaction scheme was used to obtain the total energies. RSE is relatively greater in the five-(1a-2c) compared to the six-membered ring systems except for 4b, which gives a RSE that is comparable to five-membered ring lactams. These variations were also observed in the calculated inter-atomic amide bond distances (C-N), which is why the six-membered ring lactams C-N bond are more rigid than those with five-membered ring lactams. The calculated ΔG# values from the acylation reaction of the lactams (involving the S-H group of the cysteine active residue from L,D transpeptidase 2) revealed a faster rate of C-N cleavage in the five-membered ring lactams especially in the 1-2 derivatives (17.58 kcal mol-1 ). This observation is also reflected in the calculated amide bond force constant (1.26 mDyn/A) indicating a weaker bond strength, suggesting that electronic factors (electron delocalization) play more of a role on reactivity of the β-lactam ring, than ring strain.
- Published
- 2019
45. Optimized Procedure for Recovering HIV-1 Protease (C-SA) from Inclusion Bodies
- Author
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Glenn E. M. Maguire, Thavendran Govender, Sibusiso B. Maseko, Tricia Naicker, Johnson Lin, Deidre Govender, and Hendrik G. Kruger
- Subjects
medicine.medical_treatment ,Bioengineering ,Biochemistry ,Inclusion bodies ,Analytical Chemistry ,03 medical and health sciences ,HIV Protease ,HIV-1 protease ,Escherichia coli ,medicine ,Cytotoxicity ,030304 developmental biology ,Inclusion Bodies ,chemistry.chemical_classification ,0303 health sciences ,Protease ,biology ,Chemistry ,030302 biochemistry & molecular biology ,Organic Chemistry ,Fusion protein ,Molecular biology ,Recombinant Proteins ,Enzyme ,HIV-1 ,biology.protein ,Specific activity ,Thioredoxin - Abstract
HIV-1 is an infectious virus that causes acquired immunodeficiency syndrome (AIDS) and it is one of the major causes of deaths worldwide. The production of HIV-1 protease (PR) on a large scale has been a problem for scientists due to its cytotoxicity, low yield, insolubility, and low activity. HIV-1 C-SA protease has been cloned, expressed, and purified previously, however, with low recovery (0.25 mg/L). Herein we report an optimal expression and solubilisation procedure to recover active HIV-1 C-SA protease enzyme from inclusion bodies. The HIV protease was expressed in seven different vectors (pET11b, pET15b, pET28a pET32a, pET39b, pET41b and pGEX 6P-1). The highest expression was achieved when the vector pET32a (Trx tag) was employed. A total of 19.5 mg of fusion protein was refolded of which 5.5 mg of active protease was obtained after cleavage. The free protease had a high specific activity of 2.81 µmoles/min/mg. Interestingly the Trx-fusion protein also showed activity closer (1.24 µmoles/min/mg) to that of the free protease suggesting that the pET32a vector (Trx tag) expressed in BL21(DE3) pLysS provides a more efficient way to obtain HIV-1 protease.
- Published
- 2019
46. Current trends in computer aided drug design and a highlight of drugs discovered via computational techniques: A review
- Author
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Tricia Naicker, Thavendran Govender, Glenn E. M. Maguire, Lindiwe A. Jhamba, Hendrik G. Kruger, Victor T. Sabe, and Thandokuhle Ntombela
- Subjects
Pharmacology ,Virtual screening ,Chemistry ,business.industry ,Drug discovery ,Organic Chemistry ,Drug Evaluation, Preclinical ,General Medicine ,AutoDock ,computer.software_genre ,Zinc database ,Molecular Docking Simulation ,Software ,Drug Discovery ,Computer-aided ,Computer Aided Design ,Software engineering ,business ,computer ,Density Functional Theory - Abstract
Computer-aided drug design (CADD) is one of the pivotal approaches to contemporary pre-clinical drug discovery, and various computational techniques and software programs are typically used in combination, in a bid to achieve the desired outcome. Several approved drugs have been developed with the aid of CADD. On SciFinder®, we evaluated more than 600 publications through systematic searching and refining, using the terms, virtual screening; software methods; computational studies and publication year, in order to obtain data concerning particular aspects of CADD. The primary focus of this review was on the databases screened, virtual screening and/or molecular docking software program used. Furthermore, we evaluated the studies that subsequently performed molecular dynamics (MD) simulations and we reviewed the software programs applied, the application of density functional theory (DFT) calculations and experimental assays. To represent the latest trends, the most recent data obtained was between 2015 and 2020, consequently the most frequently employed techniques and software programs were recorded. Among these, the ZINC database was the most widely preferred with an average use of 31.2%. Structure-based virtual screening (SBVS) was the most prominently used type of virtual screening and it accounted for an average of 57.6%, with AutoDock being the preferred virtual screening/molecular docking program with 41.8% usage. Following the screening process, 38.5% of the studies performed MD simulations to complement the virtual screening and GROMACS with 39.3% usage, was the popular MD software program. Among the computational techniques, DFT was the least applied whereby it only accounts for 0.02% average use. An average of 36.5% of the studies included reports on experimental evaluations following virtual screening. Ultimately, since the inception and application of CADD in pre-clinical drug discovery, more than 70 approved drugs have been discovered, and this number is steadily increasing over time.
- Published
- 2021
47. Mechanistic insight on the inhibition of D, D-carboxypeptidase from
- Author
-
Thandokuhle, Ntombela, Anya, Seupersad, Sibusiso, Maseko, Collins U, Ibeji, Gideon, Tolufashe, Siyabonga Innocent, Maphumulo, Tricia, Naicker, Sooraj, Baijnath, Glenn E M, Maguire, Thavendran, Govender, Gyanu, Lamichhane, Bahareh, Honarparvar, and Hendrik G, Kruger
- Subjects
Imipenem ,Alanine ,Acylation ,Peptidyl Transferases ,Water ,Carboxypeptidases ,Meropenem ,Mycobacterium tuberculosis ,Peptidoglycan ,beta-Lactams ,Carbon ,Anti-Bacterial Agents ,Monobactams - Published
- 2021
48. Trends in NMR Structural Elucidation Of Polycyclic Cages, Namely: Adamantane, Pentacycloundecane and Trishomocubane
- Author
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Kornelia J. Skowron, Hendrik G. Kruger, Thavenden Govender, Clayton A. Pedigo, Darcelle Dieudonné, Oluseye K. Onajole, Monsuru T. Kelani, and Tricia Naicker
- Subjects
chemistry.chemical_compound ,Chemistry ,Stereochemistry ,Adamantane ,General Chemistry - Abstract
Advances in Nuclear Magnetic Resonance (NMR) spectroscopy is a cornerstone in structure elucidation of polycyclic 'cage' scaffolds. Due to the compactness of these compounds, much overlap, as well as unique through-space and bond NMR interactions are frequently observed. This review serves as a guide for the NMR elucidation of future derivatives by providing some of the typical and relevant aspects of the characteristic trends, substituent patterns and chemical shift behaviour for the identification of the polycyclic structures, namely adamantane, pentacycloundecane and trishomocubane derivatives. Keywords: adamantane, NMR elucidation, pentacycloundecane, polycyclic compounds, trishomocubane
- Published
- 2021
49. Microwave-assisted synthesis of
- Author
-
Neliswa Z, Mhlongo, Thomas, Ebenhan, Cathryn H S, Driver, Glenn E M, Maguire, Hendrick G, Kruger, Thavendran, Govender, and Tricia, Naicker
- Abstract
In this study, a significantly improved method for the synthesis of modular meso-BODIPY (boron dipyrromethene) derivatives possessing a free carboxylic acid group (which was subsequently coupled to peptides), is disclosed. This method provides a vastly efficient synthetic route with athreefold higher overall yield than other reports. The resultant meso-BODIPY acid allowed for further easy incorporation into peptides. The meso-BODIPY peptides showed absorption maxima from 495-498 nm and emission maxima from 504-506 nm, molar absorptivity coefficients from 33 383-80 434 M-1 cm-1 and fluorescent quantum yields from 0.508-0.849. The meso-BODIPY-c(RGDyK) peptide was evaluated for plasma stability and (proved to be durable even up to 4 h) was then assessed for its fluorescence imaging applicability in vivo and ex vivo. The optical imaging in vivo was limited due to autofluorescence, however, the ex vivo tissue analysis displayed BODIPY-c(RGDyK) internalization and cancer detection thereby making it a novel tumor-integrin associated fluorescent probe while displaying the lack of interference the dye has on the properties of this ligand to bind the receptor.
- Published
- 2020
50. The development of a sub/supercritical fluid chromatography based purification method for peptides
- Author
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Hendrik G. Kruger, Thavendran Govender, Kamini Govender, Sooraj Baijnath, and Tricia Naicker
- Subjects
chemistry.chemical_classification ,Chromatography, Reverse-Phase ,Chromatography ,Tetrapeptide ,010405 organic chemistry ,Methanol ,010401 analytical chemistry ,Clinical Biochemistry ,Pharmaceutical Science ,Reproducibility of Results ,Peptide ,Chromatography, Supercritical Fluid ,01 natural sciences ,Environmentally friendly ,0104 chemical sciences ,Analytical Chemistry ,Structure and function ,chemistry ,Signalling molecules ,Drug Discovery ,Supercritical fluid chromatography ,Purification methods ,Solubility ,Peptides ,Spectroscopy - Abstract
Peptide drugs are essential components of the pharmaceutical industry with a multiplicity of therapeutic properties, such as being anti-hypertensive, anti-microbial, anti-diabetic, and having anti-cancer potential. These molecules are similar in physiological structure and function to the body's endogenous signalling molecules and are therefore ideal candidates for the development of the next-generation of drugs. However, the purification of these peptides can be problematic due to poor solubility and stability, which often results in low peptide yields. Peptides are traditionally purified via RP-HPLC methods, which are tedious and employ harsh solvents that generate harmful waste to the environment. There is a growing need for more cost-effective and sustainable purification methods of these biologics. SFC can provide a greener peptide purification approach with more environmentally friendly mobile phases such as CO2 and methanol, which can easily be recycled with minimal environmental impact. Currently, there is limited knowledge regarding the SFC purification of peptides. Herein, this study investigated SFC methods to purify a tetrapeptide (LYLV), octapeptide (DRVYIHPF), and nonapeptide (LYLVCGERG) on commercially available columns at an analytical scale. The 2-ethyl pyridine column proved to be optimal based on its reproducibility, peak shapes, efficient separations, and retention factors with peptide recoveries ranging from 80 to 102%. The run times were reduced to 13 min, as opposed to the traditional RP-HPLC methods of 50 min, thus making this SFC method an efficient, greener, and more cost-effective approach for the purification of these peptides.
- Published
- 2020
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