UWCScholar :: Browsing by Author "Onani, Martin O."

Browsing by Author "Onani, Martin O."

Now showing 1 - 16 of 16

Bis(ferrocenylimine)palladium(II) and platinum(II) complexes: synthesis, molecular structures and evaluation as antitumor agents
(Elsevier, 2012) Motswainyana, William M.; Onani, Martin O.; Madiehe, Abram M.
Compounds (ferrocenyl-2-furylmethyl)imine (L1), (ferrocenyl-2-thiophenemethyl)imine (L2) and (ferrocenyl-2-thiopheneethyl)imine (L3) were synthesized by condensation reactions and obtained in very good yields. Reactions of L1 – L3 with 0.5 equiv of either PdCl2(cod), PdClMe(cod) or K2[PtCl4] gave the new corresponding trans bis(ferrocenylimine)palladium(II) and platinum(II) complexes 1 – 9. The compounds were characterized by elemental analysis, IR, 1H and 13C NMR spectroscopy. The molecular structures of 3 and 6 were determined by single crystal X-ray diffraction analysis. Both structures crystallize in monoclinic P21/n space system. The coordination geometry around the palladium atom in complexes 3 and 6 exhibits a square planar geometry at the palladium atom. Complexes 1, 7 and 9 were evaluated for their cytotoxic activities against human breast (MCF-7) and human ovarian (A2780) cancer cell lines, and they exhibited low cytotoxic activities but comparable to that of cisplatin.
Covid-19 and cancer therapy: Interrelationships and management of cancer cases in the era of Covid-19
(Hindawi, 2021) Mbugua, Simon N.; Njenga, Lydia W.; Onani, Martin O.
'e COVID-19 global epidemic poses this generation’s biggest worldwide public health challenge probably since the 1918 influenza epidemic. Recent reports on two new variants have triggered a dramatic upsurge in research to understand the pandemic, primarily focussing on the virology, triggers, clinical characteristics, and diagnostic tests including the prevention and management of the novel coronavirus. Whilst such studies are important in managing the present medical emergency, there is a need for further work to include interdependencies between the epidemic and other illnesses. 'is will help in developing effective approaches to treat and manage associated diseases in both the short and the long term. In this regard, people living with cancer are a subgroup that is highly vulnerable to respiratory infections and acute pneumonitis similar to the one caused by the COVID19 virus. 'is is because the state of their immunity is compromised due to malignancy and the adverse effects of anticancer treatments. With annual cancer projections rising globally and an estimated 70 percent of all cancer-related deaths occurring in low- and middle-income countries, the patient population with impaired immune systems that could be adversely impacted by COVID-19 is only anticipated to rise. In this review, we delve into the challenges and health risks facing cancer patients and cancer treatment in the COVID-19 context, with suggestions into viable measures which can be taken to minimize exposure to the risk of contracting COVID-19 for this vulnerable subgroup. New mutations and the prospects offered by vaccines development and how they relate to this class of patients are also discussed.
Dichlorido-[(2-diphenylphosphino-benzylidene)-2-methylphenylen-amine]palladium( II) acetonitrile monosolvate
(International Union of Crystallography, 2013) Motswainyana, William M.; Onani, Martin O.; Jacobs, Jeroen; van Meervelt, Luc
The title imino–phosphine compound, [PdCl2(C26H22NP)] - CH3CN, was prepared by reaction of N-[2-(diphenylphosphanyl) benzylidene]-2-methylaniline with dichlorido(cycloocta- 1,5-diene)palladium(II) in dry CH2Cl2. The PdII cation is coordinated by the P and N atoms of the bidentate chelating ligand and by two chloride anions, generating a distorted square-planar coordination geometry. There is a detectable trans influence for the chloride ligands. The methyl group present in this structure has an influence on the crystal packing.
Dichlorido-[2-(2,6-diethylphenyl)iminomethylquinoline-N,N’]palladium(II) acetonitrile monosolvate
(International Union of Crystallography, 2012) Motswainyana, William M.; Onani, Martin O.; Jacobs, Jeroen; van Meervelt, Luc
The title complex, [PdCl2(C20H20N2)] CH3CN, was synthesized by the reaction of 2-[(2,6-diethylphenyl)iminomethyl]quinoline with dichlorido(cycloocta-1,5-diene)palladium(II) in dry CH2Cl2. The PdII ion is coordinated by two N atoms of the bidentate quinoline ligand and by two chloride anions, generating a distorted square-planar coordination geometry around the metal centre. There is a detectable trans influence for the chloride ligands. The crystal packing is characterized by – stacking between the quinoline rings. The use of acetonitrile as the crystallization solvent was essential for obtaining good-quality crystals.
Effect of growth temperature on the structural, optical and luminescence properties of cadmium telluride nanoparticles
(Springer, 2018) Kiprotich, Sharon; Onani, Martin O.; Dejene, Francis B.
Cadmium telluride (CdTe) has been successfully prepared by a simple wet chemical process at different reaction temperatures. Temperature is one parameter that thermodynamically plays an important role in controlling the growth rate, morphology, size and size distribution of the as-prepared nanoparticles (NPs). Effect of this parameter was investigated on the growth, structural and optical properties of CdTe NPs. It was observed that the Powder X-ray diffraction (XRD) pattern for samples prepared at 50 °C had many impurities from unreacted precursors while those prepared at > 100 °C displayed polycrystalline NPs. The XRD results revealed that the structure of the CdTe NPs was cubic with the planes (111), (220), (311) being the main observed peaks. The crystallite sizes obtained from Scherrer formula increased with the increase in growth temperature (2.86–3.62 nm grown at 50–200 °C respectively). The scanning electron microscopy micrographs showed that the morphology of the nanoparticles possessed spherical-shaped particles over the entire surface. This was further confirmed by high resolution transmission electron microscopy micrographs which also displayed increase in the particle size with an increase in the growth temperature. In the optic study, the photoluminescence (PL) spectra displayed a red shift (540–560 nm) in emission as growth temperature increased from 50 to 200 °C. The highest PL peak intensity was realized at a growth temperature of 150 °C. Absorption band maxima were observed to shift towards longer wavelength for higher growth temperatures. The optical band gap decreased with increase in the growth temperature from 2.67 to 2.08 eV for 50–200 °C respectively.
The identification of aptamers against serum biomarkers of human tuberculosis
(University of the Western Cape, 2018) Martin, Darius Riziki; Meyer, Mervin; Onani, Martin O.
Tuberculosis (TB) is a global health problem and rated as the second leading cause of death after HIV/AIDS. Transmission of TB from one person to the next is very rapid in crowded communities. Therefore, it is crucial to identify people who are infected as quickly as possible not only to provide treatment but also to prevent the spread of the disease. Current TB diagnostic tests such as the culture and sputum smear tests are time-consuming, while rapid tests make use of antibodies that are costly and have low sensitivity and stability. Great improvement has been observed when aptamers are used in place of antibodies in rapid diagnostic tests such as lateral flow devices (LFDs). Therefore, the current study aims to synthesize and identify aptamers against serum biomarkers for development of rapid TB diagnostic tests such as a lateral flow assay. Several TB serum biomarkers have been identified and can be used for the diagnosis of TB. TB biomarkers expressed in serum samples were identified through in silico approach. The biomarkers were expressed in bacterial systems using recombinant DNA technology. The recombinant proteins were purified by affinity chromatography and further used as targets for the selection of aptamers using Systemic Evolution of Ligands by EXponential enrichment (SELEX). Aptamers for the selected biomarkers were synthesized based on magnetic-bead based SELEX and characterized by electrophoretic mobility shift assay (EMSA), Surface Plasmon resonance (SPR) and MicroScale Thermophoresis (MST). Six putative TB serum biomarker proteins were selected from literature, namely, Insulin-like Growth Factor Binding Protein 6 (IGFBP6), Interferon-stimulated Gene 15 (ISG15), Calcium Binding Protein (S100A9), Retinol Binding Protein 4 (RBP4), Granzyme A (GrA), and Transgelin-2 (TAGLN2). The biomarkers were recombinantly expressed and purified after which they were used as targets in SELEX for aptamers synthesis. Aptamers were analysed by in silico method and the ones with highly conserved motifs were selected. The selected aptamers were synthesized and later characterized. The aptamers that show high affinity and specificity for the biomarkers will be used for the fabrication of a rapid lateral flow device for TB screening. Such a test would allow for a short diagnostic turnaround time, and hence expedite treatment.
Imino-phospine palladium (II) and platinum (II) complexes: Synthesis, molecular structures and evaluation as antitumor agents
(Elsevier, 2013) Motswainyana, William M.; Onani, Martin O.; Madiehe, Abram M.; Saibu, Morounke; Thovhogi, Ntevheleni; Lalancette, Roger A.
The imino-phosphine ligands L1 and L2 were prepared via condensation reaction of 2-(diphenylphosphino) benzaldehyde with substituted anilines and obtained in very good yields. An equimolar reaction of L1 and L2 with either PdCl2(cod) or PtCl2(cod) gave new palladium(II) and platinum(II) complexes 1–4. The compounds were characterized by elemental analysis, IR, 1H and 31P NMR spectroscopy. The molecular structures of 2, 3 and 4 were confirmed by X-ray crystallography. All the three molecular structures crystallized in monoclinic C2/c space system. The coordination geometry around the palladiumand platinumatoms in respective structures exhibited distorted square planar geometry at the metal centers. The complexes were evaluated in vitro for their cytotoxic activity against human breast (MCF-7) and human colon (HT-29) cancer cells, and they exhibited growth inhibitory activities and selectivity that were superior to the standard compound cisplatin.
Imino-quinolyl palladium(II) and platinum(II) complexes: synthesis, characterization, molecular structures and cytotoxic effect
(Elsevier, 2013) Motswainyana, William M.; Onani, Martin O.; Madiehe, Abram M.; Saibu, Morounke; Jacobs, Jeroen; van Meervelt, Luc
Imino-quinolyl ligands L1-L5 were synthesized by condensation reactions and obtained in good yields. Reactions of the ligands with either PdCl2(cod) or K2[PtCl4] gave the corresponding palladium(II) and platinum(II) complexes 1-10 also in good yields. All the compounds were characterized by elemental analysis, IR, 1H and 13C NMR spectroscopy. X-ray crystallography was used to confirm the structures of these compounds. Molecular structures of 3 and 5 showed that the ligands coordinate to the metal centre through the two nitrogen atoms, generating a distorted square planar geometry around the palladium atom. The new complexes exhibited remarkable cytotoxic activities against MCF-7 and HT-29 cancer cell lines.
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.
New imino-pyridyl nickel (II) complexes: synthesis, molecular structures and application as Heck coupling catalysts
(Elsevier, 2012) Motswainyana, William M.; Onani, Martin O.; Ojwach, Stephen O.; Omondi, Bernard
Reactions of imino-pyridyl ligands, (2-pyridyl-2-thiophenemethyl)imine (L1) and (2-pyridyl-2-thiopheneethyl)imine (L2) with NiBr2(DME) gave the corresponding complexes [Ni(L1)Br2] (1) and [Ni(L2)Br2] (2) in good yields. Treatment of 1 and 2 with one equivalent of 2-hydroxythiophenol resulted in the displacement of the bromide ligands to form the nickel(II) thiolato complexes 3 and 4. Molecular structure of 3 confirmed that L1 and L2 bind to the nickel atom in a bidentate fashion. Complexes 1-4 catalyzed the Heck coupling reaction of iodobenzene and bromobenzene with methyl acrylate.
New phenylene bridged binuclear bis (imino-quinolyl) palladium(II) complexes: synthesis, characterization and Heck reactions
(Elsevier, 2012) Motswainyana, William M.; Onani, Martin O.
Two new phenylene bridged binuclear bis(imino-quinolyl) palladium (II) complexes were prepared from the reaction of the ligand 1,4-bis(imino-quinolyl)benzene, L1 with either Pd(cod)Cl2 or Pd(cod)ClMe. The molecular structure of L1 was confirmed by single crystal X-ray diffraction analysis. The structure shows two planar molecules (A and B) in the asymmetric unit. The complexes were evaluated as catalysts for Heck coupling reactions of methyl and butyl acrylate with iodobenzene, and showed high activity. The reactions proceeded at a faster initial rate and there was good selectivity for the formation of the trans- isomers.
Novel gold nanoparticles of drought tolerance enabler GYY4137
(University of the Western Cape, 2019) Binase, Ntombikayise; Ludidi, Ndiko N.; Onani, Martin O.
Different nanoparticles have the ability to improve plant tolerance to drought stress. In the study we report for the first time novel morpholin-4-ium 4-methoxyphenyl (morpholino) phosphinodithioate capped- gold nanoparticles (GYY4137-capped AuNPs). The GYY4137 is a slow releasing hydrogen sulfide (H2S) donor. The GYY4137 AuNPs compared to preliminary experiments of L-serine and L-threonine gold nanoparticles. The nanoparticles were prepared using a simple reflux reduction method in a rolling boil flask at 80 oC. The uncapped GYY4137-AuNPs were relatively stable and had surface plasmon resonance at 562 nm compared to 524 nm and 560 nm of serine-AuNPs and threonine-AuNPs. The nanoparticles were capped with different concentrations (0.1-5 %) of water-soluble poly (ethylene) glycol (PEG) (Mw300) and 0.2% chitosan. The PEG did not fully encapsulate the gold nanoparticles, while the chitosan successfully produced positively charged gold nanoparticles. The formation of chitosan capped GYY4137-AuNPs were verified with UV-Visible spectroscopy (UV-Vis), High Resolution Transmission electron microscopy (HRTEM), Dynamic Light scattering (DLS) and the Zetasizer. The UV-Vis, HRTEM and STEM verified chitosan capped nanoparticles had a surface plasmon resonance peak at 560 nm, with icosahedral, tetrahedron and spherical shaped nanoparticles as the serine-AuNPs that absorb at 560 nm. The agglomerated threonine-AuNPs had a maximum absorbance peak at 524 nm. The chitosan GYY4137-AuNPs had hydrodynamic size of 347.9 nm and zeta potential of + 47 mV, while serine-AuNPs and threonine-AuNPs had hydrodynamic size of 110 nm, zeta potential of -2.9 mV and -230 mV respectively. The polydispersity index (PDI) of the chitosan capped gold nanoparticles was 0.357 compared to 0.406 of both the amino acid gold nanoparticles. The polydispersity index (PDI) showed that the nanoparticles were polydispersed nanoparticles with broad size range as confirmed by the HRTEM and STEM results/ of chitosan capped GYY4137-AuNPs. The sizes of the nanoparticles were 100 nm and 60 nm for GYY4137-AuNPs while the size serine-AuNPs were 60 nm. The gold nanoparticles structural compositions were further confirmed by energy-dispersive X-ray spectrometry (EDX) and Attenuated total reflection infrared spectroscopy (ATR-IR). EDX results proved successful gold nanoparticles synthesis by presence of the element Au in all three nanoparticles and the chitosan GYY4137-AuNPs had 48. 56 wt. % of gold. The FTIR-ATR new bands formation shows that new chemical bonds are formed between the reducing agents, the precursor gold salt solution and capping agents. The shifts showed successful encapsulation with chitosan in GYY4137-AuNPs. The chitosan encapsulation improved surface charge and reactivity of the gold nanoparticles to improve delivery of the hydrogen sulfide donor GYY4137 for later applications to plants.
One-pot synthesis and characterization of InP/ZnSe semiconductor nanocrystals
(Elsevier, 2013) Mushonga, Paul; Onani, Martin O.; Madiehe, Abram M.; Meyer, Mervin
We report on the one-pot synthesis of InP/ZnSe quantum dots (QDs) using a precursor-based colloidal synthesis in a noncoordinating solvent environment. The structural and optical studies were carried out on the as-prepared InPQDs. The quantum yield of the nanocrystals was recorded as 6% and a 1.4 times reduction in the ratio of trap-related emission to band edge emission was observed on ZnSe passivation of the InPQDs.
Synthesis, characterization, and molecular docking of novel 4-Aminoquinolines and Salicylaldimine complexes: evaluation as antimalarial and antitumor agents
(University of the Western Cape, 2016) Busa, Asanda V.; Onani, Martin O.
Malaria remains a major global health problem and to date, hundreds of thousands of people die as a result of this disease every year. Malaria has been able to adapt and rebound despite various efforts made to combat the disease. The decrease in efficacy of many front-line drugs against malaria, due to increased resistance, prompts investigation into obtaining effective compounds that are able to overcome this resistance. This study investigated the synthesis, characterisation and biological evaluation of new quinoline (as antimalarial agents) as well as non-quinoline (as antitumor agents) based compounds.
Synthesis, characterization, and study mode of coordination of N,N’- and N,O - (arene)ruthenium II complexes co-ligated by isoniazid: Preparation for antimicrobial studies
(University of the Western Cape, 2018) Diyoka, Nkongolo Jean Blaise; Onani, Martin O.
This thesis reports on the syntheses of complexes of (arene) ruthenium (II) isoniazid Schiff base ligands for antimicrobial studies. Isoniazid Schiff base ligands; isonicotinyl acid (2-hydroxy-5- methyl-benzilidene)-hydrazide (L1), isonicotinyl acid (2-hydroxy-5-methoxy-benzilidene)- hydrazide (L2), isonicotinyl acid (-5-chloro-2-hydroxy-benzilidene)-hydrazide (L3), isonicotinyl acid (-5-bromo-2-hydroxy-benzilidene)-hydrazide (L4), isonicotinyl acid (2-hydroxy-5-nitrobenzilidene)- hydrazide (L5) were prepared by condensation reaction under reflux from equimolar amounts of isioniazid, which is an amine, with five different aldehyde moieties. Ruthenium (II) complexes of these isoniazid Schiff base ligands (C1 - C5) were prepared in an ethanolic solution under reflux and inert atmosphere at 60°C using Schlenk techniques. Fourier transform infrared spectroscopy (FTIR), ultraviolet – visible spectroscopy, thermogravimetric analysis, nuclear magnetic resonance and elemental analysis were the characterization techniques that confirmed the successful preparation of the ligands. All the ligands spectra displayed the imine functional group peak which confirmed the successful preparation. The ligands L1 – L5 and the complexes C1 – C5 were subjected to similar characterization techniques which further confirmed the successful syntheses and the coordination of metal and ligand by displaying a shift in their respective imine peaks and transitions values. All the synthesized compounds were subjected to a standard antimicrobial test using three microorganisms, Staphylococcus aureus, Methicillin resistant Staphylococcus aureus and Pseudomonas aeruginosa. Out the ten compounds tested, only ligand L5 gave the best results against Staphylococcus aureus.
Synthesis, spectroscopic characterization, and cyclic voltammetry studies for salicylaldehyde schiff base ligands and their copper (ii) salicylaldimine compounds
(University of the Western Cape, 2022) Booysen, Siyasanga; Onani, Martin O.
Schiff base compounds are a significant class of ligands in coordination chemistry which have been applied widely as they are precise and versatile towards different metal salts. These compounds could be commonly chelating operators, particularly when a compound attached like hydroxide or alkyl thiols (– OH or – SH) is available near the azomethine group to form a five or six-membered ring with the metal center. The metal complexes of Schiff bases contracted from substituted salicylaldehydes, particularly the heterocyclic based metal complexes and different amines have been highly explored due to their broad applicability in mild oxidation catalysis.

Browsing by Author "Onani, Martin O."

Results Per Page

Sort Options