In view of the increasing importance of thiophene derivatives as chemotherapeutic agents, it was considered of interest to apply the Reformatsky reaction to the synthesis of compounds containing the thiophene nucleus with the thought that these might serve as intermediates for further syntheses.

Submitted in fulfilment of the requirements of the Degree of Master of Technology: Chemistry, Durban University of Technology. 2014. / In this study, we report the synthesis of three quinolone bearing imidazole derivatives 2, 3 and 4 and two quinolone bearing BODIPY dyes 5 and 7. In the synthesis of 2, 3 and 4, the first step was the preparation of the starting compound 2-chloro-3-formyl quinoline (1); the Vilsmeier-Haack cyclisation protocol was used. Compound 1 was used with the appropriate diamine, together with POCl3 to produce 2, 3 and 4. These compounds were characterized by IR, 1H-NMR and 13C-NMR. In the synthesis of 5, compound 1 was used whilst 6 was used for the synthesis of 7. This was via. a one-pot synthesis using conventional reflux apparatus and Schlenk technique. These compounds were characterized by IR, 1H-NMR and 13C-NMR. Four other BODIPY dyes were also synthesized but their purification by column chromatography were unsuccessful. However a HPLC method was developed using 2 as a model; the best eluting solvent was 65 % methanol. After synthesis, 2, 3, 4, 5 and 7 were used for spectroscopic studies by UV-visible and fluorescence spectroscopy. In the UV-visible studies, 2, 3 and 4 were dissolved, separately, in five solvent viz. ethanol, methanol, dichloromethane, chloroform and acetonitrile. The UV profile of each compound was obtained and the maximum absorbance was then used for fluorescence studies. In the fluorescence studies, all the compounds displayed a fluorescence nature when excited with the various wavelengths. The fluorescence properties, namely Stoke shift, quantum yield, life time, molar absorptivity and brightness, were investigated to establish the properties of each compound in all five solvent systems. The Stoke shift was evident in all compounds and the quantum yields were below one which indicates no other electron transfer mechanisms occurring. The results displayed a favorable response and this further lead to analysis of the synthesized compounds for it potential application as a chemosensor. Eight metal ions were used to investigate this property. All eight metal ions, when reacted with the synthesized compounds, as ligands, showed chemosensor properties, viz. photon induced electron transfer, inter-molecular charge transfer and fluorescence resonance electron transfer, as a quenching and enhancement of emission and excitation peaks were observed. The compounds were further investigated for its potential for its use as a photovoltaic cells. The energies of the compounds were obtained from the analyses of the reflectance and transmission spectra. It was found that the synthesized compounds displayed properties which were positive for its use as a photovoltaic cell. Biological analyses using molecular docking analyses and MTT assays were conducted to determine the use of these as an anti-cancer drug. Compounds 2 and 3 formed hydrogen bonds with GLU 25 and LEU 27, respectively with MDM2-p53 proteins. Following the molecular docking studies, the MTT assay was performed on all five synthesized compounds. The BODIPYs with the quinoline moieties demonstrated a reduction in the rate of A549 cell proliferation when compared to the imidazole and benzimidazoles; this was observed for compounds 5 and 7. Further, a comparison between imidazoles clearly shows that compounds 3 and 4 also decreased cell proliferation. In contrast compound 2 exhibited an increased rate of cell proliferation. The optical density of the control cell, is much higher that the plates for concentration 31.25 µg/ mL to 500 µg/ mL. However 2 cannot be discarded; this compound clearly shows that it possesses anti-hyperglycaemic properties and further studies are recommended.

Pyrrolobenzodiazepine (PBD) derivatives interact with the minor-groove of DNA to form mono-adducts (monomers) or cross-links (dimers). They show remarkable activity in vitro and in vivo in a wide range of tumour types and one dimer, SJG-136 is currently in clinical development. Preclinical studies have shown that SJG-136 is a P-gp substrate limiting its anti-tumour activity. The work presented in this thesis identifies key physicochemical properties influencing both the interaction of PBDs with ABC transporters P-gp, MRP1 and BCRP and their growth inhibitory potency. A testable hypothesis for further optimisation of PBDs is proposed. The biological activity of 4 dimers and 12 monomers was assessed using several in vitro models presenting differential expression of ABC transporters. Biological endpoints were the growth inhibitory effect determined using a sulforhodamine B assay and γ-H2AX foci formation. In addition PBD transport was evaluated using a Caco-2 transwell assay. P-gp substrate specificity was restricted to dimers. The MW, the number of (N+O) atoms (>8), a polar surface area (>75 Ǻ2) and hydrogen bonding energy (>10) could discriminate substrates among the PBDs. P-gp polymorphism was also evaluated. The mutation in position 2677 (G/T) was associated with reduced sensitivity to the PBDs. When combined mutations in position 3435/2677 were linked, the transporter abrogated this apparent gain of function. The impact of MRP1 was identified for all dimers and 1/12 monomers. In addition, the cooperative role of glutathione in the resistance mediated by MRP1 to the PBDs was revealed. The presence of a carbonyl moiety at the extremity was shown to discriminate the 7 substrate for MRP1 among the monomers. A structure-activity-relationship study showed that negatively charged (N+O) atoms and a greater number of aromatic rings confer greater dependency to BCRP. BCRP polymorphism was also evaluated. The T482 mutant was associated with an increase in drug transport. The cytotoxicity of the PBDs correlated to the interaction of the DNA as measured by ΔTm. Compounds, being non surface active, with a greater polar surface area and number of aromatic rings and a lower solvent accessible surface area were associated with a greater cytotoxicity. Van-der-waals energy and the electrostatic forces were identified in silico as predictable features involved in the DNA binding. New PBDs were designed and were predicted to be associated with a greater affinity for DNA and with minimal interaction with ABC transporters.

published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

No description available.

No description available.

Submitted in partial fulfillment for the Degree of Master of Applied Sciences in Biotechnology, Durban University of Technology, Durban, South Africa, 2016. / Coumarins are naturally occurring α-benzopyrone derivatives known for their pharmacological properties such as anticoagulant, antimicrobial, anticancer, antioxidant, anti-inflammatory and antiviral properties. The pharmacological, biochemical, and curative applications of coumarins depend on the substitution around the coumarin core structure. In the present study, seven halogenated coumarins CMRN1 - CMRN7 were synthesized and evaluated for mosquito larvicidal, repellancy , and insecticidal activity against Anopheles arabiensis. Furthermore, the antimicrobial properties of compounds CMRN1 - CMRN7 were evaluated by assessing the bacterial and fungicidal activities using the disc diffusion method. The anti-inflammatory properties were evaluated using the 5-lipoxygenase kit assay. The evaluation of the safe use of the compounds was determined using the Brine shrimp lethal test. The potential carcinogenic properties of the studied compounds was done using the Salmonella mutagenicity test. The anti-cancer property of the studied compounds was evaluated against UACC62 (Melanoma), MCF-7 (Breast cancer), and PBMC (Peripheral blood mononuclear) cell lines using of MTT assay. The apoptotic potential of the synthesized coumarin was evaluated against UACC62 (Melanoma) cell by assessing their morphological changes, membrane change, mitochondria membrane potential, and caspase-3 activity using the Annexin V-PI staining, JC-1, caspase-3 enzyme kits, respectively, on flow cytometer. The results were compared to a known anti-cancer drug, doxorubicin. The results showed that compounds CMRN1, CMRN2, CMRN4, CMRN5 and CMRN7 exerted 100% larval mortality within 24 h of exposure. All halogenated coumarins reversibly knocked down adult mosquitoes but did not kill them after 24 h of exposure. Furthermore, the adulticidal activity of the compounds was considered only mild to moderate. The antimicrobial activity of the synthetized coumarins CMRN1 - CMRN7 were assessed against E. coli, K. pneumoniae, S. marcescens, S. faecalis, B. cereus, B. coagulans, B. stearothermophilus, C. freundii, S. aureus and M. luteus bacteria and three yeast cultures, C. albicans, C. utilis, S. cerevisiae as well as two fungal species, A. flavus and A. niger. Compounds CMRN1 and CMRN2 showed bacterial growth inhibition for all the tested species except K. pneumonia and B. stearothermophilus. Compounds CMRN4 and CMRN7 showed moderate bacterial inhibition against B. cereus, M. luteus and S. aureus. The anti-inflammatory activity of the coumarins analogues showed that 1 mg/mL of the compounds CMRN1, CMRN2, CMRN4 and CMRN5 displayed moderate anti-inflammatory activity when compared to the positive control, 15-lapoxygenase. The cytotoxicity results of the studied synthetized coumarins displayed selective activity towards the cancer cell lines used in this study. Our studies showed that CMRN1, CMRN2, CMRN4, and CMRN5 had significant cytotoxity effect against UACC-62 (Melanoma) and MCF-7 ( Breast) cancer cells with an inhibitory concentration (IC50) which displayed significant cytotoxicity effect, in particular CMRN4 and CMRN5. These compounds CMRN1- CMRN7 showed no toxicity effect against PBMCs cell line. The mechanism of cell death, that is, necrosis or apoptosis induced by the coumarins was investigated against UACC-62 (Melanoma). We found that CMRN1, CMRN2, CMRN4, CMRN5 induced morphological changes, characteristic of apoptosis . Annexin V kit showed that CMRN1, CMRN2 and CMRN5 showed early apopotosis and late apoptosis was particularly higher for compound CMRN4. The disruption of the mitochondria membrane was noticed to be greater in CMRN1 and CMRN5 when compared to the positive control doxorubicin. Compound CMRN4 produced high levels of caspase-3 positive compared to the control. The coumarin compounds showed no mutagenicity and were also found to be non-toxic to brine shrimps. In conclusion, compounds CMRN1, CMRN2, CMRN4, CMRN5 and CMRN7 are potential larvicidal agents because they exhibited close to 100% activity within 24 h. Furthermore, the anti-cancer efficiency of compounds CMRN1, CMRN2, CMRN4, and CMRN5, is enough qualification for them to be optimized for increase anticancer potency. / M

Submitted in complete fulfillment for the Degree of Master of Applied Sciences in Biotechnology, Durban University of Technology, Durban, South Africa, 2016. / Piperidine derivatives are essential heterocyclic compounds that have beneficial roles in the medical and commercial sector. They can be isolated from plant material and can be chemically synthesised using simple cost efficient methods. Piperidines and their derivatives are clinically used to prevent postoperative vomiting, facilitate radiological evaluation, correct gastrointestinal function as well as speed up gastric emptying before anaesthesia. Piperidine derivatives also demonstrate a wide spectrum of biological activities which include; antimicrobial, anticancer, anti- TB, anti-HIV, anti-inflammatory, analgesic, anti-influenza, anti-inflammatory and antitumor activity. The properties of piperidine derivatives depend on the nature of the side chains and their orientation. Based on the promising data that demonstrated the synergistic effects of biological agents with piperidine derivatives, the aim of our research is to determine the pharmacological activities, i.e. (i) antimicrobial activity, (ii) anti-inflammatory, (iii) anti-oxidant activity, (iv) cytotoxicity, and (v) biosafety of six piperidine derivatives, PM1 to PM6. All six piperidine derivatives (PM1-PM6) screened for antimicrobial activity exhibit characteristics of varying degrees of microbial inhibition against some Gram-positive and Gram-negative bacteria (B. cereus, B. subtilis, E. coli, S. aureus, Kl. Pneumonia, M. liuteus and P. aurenginosa) with the exception of B. polymixa, S. marcescens and S. faecalis. Certain piperidine derivatives did not demonstrate high inhibition activity towards the fungal strains, with inhibition only shown against four fungal species; A. niger, A. flavus, C. albicans and S. cerevisiae. Thus it is proposed that minor changes could be made to the structure of the compounds so that they can alter the effect that the compounds have on the specific fungi strains. With regard to antioxidant activity it is noted that the concentrations of the test compounds are directly proportional to the percentage of scavenging capacity. In comparison of the piperidine derivatives (PM1-PM6) to Rutin (reference standard), it was illustrated that Rutin displayed the best antioxidant activity. All six piperidine derivatives (PM1-PM6) showed greater than 50% anti-inflammatory activity, whilst the anti-inflammatory reference standard NCGA displayed the greatest activity in comparison to the piperidine derivatives tested. The safety of the piperidine derivatives was tested by assaying cytotoxicity, against melanoma, MCF7 cancer cells and normal fibroblasts as well as Brine shrimp lethality assay. All piperidine derivatives demonstrated high cytotoxicity activity against both cancer cell lines (melanoma and MCF7) and around 50 – 52% cytotoxicity against healthy cells. Chloro substitution of the phenyl ring increases cytotoxicity of compounds (Aerluri et al., 2012). This compound can be used in the treatment of cancer cells while inhibiting 50% of normal cells. All six piperidine derivatives (PM1-PM6) were also tested for toxicity against Artemia salina in a brine shrimp lethality assay. Piperidine derivatives exhibited varying degree of toxic activity towards the shrimp, with all derivatives displaying ± 50% toxic activity at 1000 µg/mL. These results reveal a directly proportional relationship between concentration of drug and toxicity. It remains a future research objective to modify these piperidine compounds (PM1-PM6) chemically to produce more derivatives for further biological evaluation. All the studied piperidine compounds have possible leads for optimization to carry out pre-clinical trials. We can conclude that the substitution of different side chains on the piperidine nucleus results in varying degree of pharmacological activity. Also, compounds containing the substitution of a chloro group at position 4 and a fluoro group at position 2 on the phenyl ring attached to carbon 2 and 6 on the piperidine nucleus resulted in high pharmacological activity. This good pharmacological activity was also exhibited by compounds containing substitutions of a methoxy group at position 3 on the phenyl ring attached to carbon 1 and 6 on the piperidine nucleus. Compounds containing a methoxy group positioned at carbon 4 on the phenyl ring which is attached to carbon 1 and 4 on the piperidine nuleus presented low pharmacological activity. Low activity was also exhibited by compounds containing substitution of a cyano group at position 4 on the phenyl ring which is attached to carbon 2 and 6 on the piperidine ring and a methyl group at position 4 on the phenyl group attached to a nitrogen at position 1 on the piperidine nucleus. / M

This Thesis describes the preparation and characterisation of a range of titanium imido complexes supported by a cyclopentadienyl-amidinate ligand set. Reactivity studies of these complexes towards unsaturated organic species are presented. <strong>Chapter 1</strong> reviews transition metal complexes containing imido, cyclopentadienyl, and amidinate ligands, with an emphasis on recent work. <strong>Chapter 2</strong> describes the synthesis and characterisation of titanium cyclopentadienyl imido amidinate complexes, along with precursor complexes which have not been previously reported. X-ray crystal structures of four imidotitanium species are described. <strong>Chapter 3</strong> describes the reactivity of titanium cyclopentadienyl imido amidinate complexes towards carbon dioxide. An unprecedented reaction with two molecules of carbon dioxide is reported for the arylimido complexes. X-ray crystal structures of two of the arylimido dicarboxylate products are described. The kinetics of the insertion of the second molecule of carbon dioxide are investigated and reported. <strong>Chapter 4</strong> describes the reactivity of titanium cyclopentadienyl imido amidinate complexes towards isocyanates and carbodiimides. The X-ray crystal structures of two N, O- bound ureate complexes are described. A new series of reactions involving two molecules of p-tolyl isocyanate with arylimido complexes is reported. Reactions of isocyanates with carbamate complexes are also reported. <strong>Chapter 5</strong> explores the reactivity of titanium cyclopentadienyl imido amidinate complexes towards sulfur-containing substrates. Comparisons are drawn with the reactivity towards oxygen-bearing homologues. X-ray crystal structures of two bridging sulfido complexes are described. <strong>Chapter 6</strong> discusses the reactivity of titanium cyclopentadienyl imido amidinate complexes towards substrates containing only one unsaturated linkage. Reactions with organic carbonyls and terminal alkynes are found to afford equilibria rather than isolable products. <strong>Chapter 7</strong> details full experimental procedures for all syntheses and reactions described in the text. <strong>Chapter 8</strong> contains characterising data for all new compounds reported. Full tables of crystallographic data for all new crystallographically characterised complexes described herein are presented in <strong>Appendices A-H, J-M</strong>. <strong>Appendix I</strong> contains kinetics data relating to work discussed in Chapter 3.