Synthesis, characterisation and evaluation of benzoxaborole-based hybrids as antiplasmodial agents
- Authors: Gumbo, Maureen
- Date: 2017
- Subjects: Malaria Chemotherapy , Antimalarials , Boron compounds , Drug resistance , Plasmodium falciparum , Drug development
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/59193 , vital:27456
- Description: Malaria is a mosquito-borne disease, which continues to pose a threat to the entire humanity. About 40% of the world population is estimated to be at risk of infections by malaria. Despite efforts undertaken by scientific community, government entities and international organizations, malaria is still rampant. The major problem is drug resistance, where the Plasmodium spp have over the past decades developed drug resistance against available drugs. In order to counter this problem, novel antimalarial drugs that are efficacious and with novel mode of action are of great necessity. Benzoxaborole derivatives have been shown to exhibit promising antimalarial activity against Plasmodium falciparum strains. Previous studies reported on the compounds such as 6-(2- (alkoxycarbonyl)pyrazinyl-5-oxy)-1,3-dihydro-1-hydroxy-2,1-benzoxaboroles, which showed good antimalarial activity against both W7 and 3D7 strains without significant toxicity. On the other hand, chloroquine (CQ) and cinnamic acids have a wide variety of biological activity including antimalarial activity. Herein, a hybridisation strategy was employed to synthesise new CQ-benzoxaborole and cinnamoyl-benzoxaborole hybrids. CQ-Benzoxaborole 2.12a-c and cinnamoylbenzoxaborole 2.11a-g hydrid molecules were synthesised in low to good yields. Their structural identities were confirmed using conventional spectroscopic techniques (1H and 13C NMR, and mass spectrometry). CQ-benzoxaborole compounds, however, showed instability, and only 2.12b was used for in vitro biological assay and showed activity comparable to CQ. Furthermore, in vitro biological assay revealed that compounds 2.11a-g poorly inhibited the growth of P. falciparum parasites. Interestingly, these compounds, however, exhibited satisfactory activity against Trypanosoma brucei with IC50 = 0.052 μM for compound 2.11g. The cell cytotoxicity assay of all final compounds confirmed that all CQ-benzoxaborole 2.12b and cinnamoyl-benzoxaborole 2.11a-g hybrids were non-toxic against HeLa cell lines. However, efforts to further expand the structure-activity relationship (SAR) of CQbenzoxaborole by increasing the length of the linker with one extra carbon (Scheme 2.10) were not possible as an important precursor 6-formylbenzoxaborole 2.29 could not be synthesized in sufficient yields. , Thesis (MSc) -- Faculty of Faculty of Science, Chemistry, 2017
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Synthesis, characterisation and evaluation of ferrocene-containing Novobiocin analogues for anticancer and antiplasmodial activity through inhibition of Hsp90
- Authors: Mbaba, Mziyanda
- Date: 2017
- Subjects: Antibiotics Synthesis , Ferrocene , Heat shock proteins , Antimalarials , Cancer Chemotherapy
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/65111 , vital:28690
- Description: Novobiocin (Nb) is a coumarin type antibiotic isolated from the bacterium species of Streptomyces and possesses modest anticancer and antimalarial activities. Nb and analogues have been extensively explored as potential anticancer agents through inhibition of the C- terminal domain of heat shock protein 90 (Hsp90), which plays a pivotal role in the proteinfolding machinery of cells. There has been little effort in the exploration of Nb and derivatives for antimalarial activity. Incorporation of organometallic units, such as ferrocene (Fc), into bioactive chemical scaffolds remains an attractive approach for developing new therapeutic agents for treatment of several ailments. The current study sought to investigate the anticancer and antiplasmodial effects of incorporating ferrocene (Fc) into Nb scaffold presumably through inhibition of Hsp90. The ferrocenyl Nb analogues containing simplified structural motifs such as phenyl, benzyl, and piperidine were synthesized in six to nine steps employing conventional synthetic organic protocols adapted from literature, and the compounds were accessed in reasonable yields. For comparison purposes, a selection of organic Nb analogues were also included in the study. The target compounds were characterized by spectroscopic techniques including 1-dimensional nuclear magnetic resonance (1D NMR) and high-resolution mass spectroscopy. The synthesized compounds were evaluated in vitro for potential anticancer and antiplasmodial activities using the breast cancer cell line (HCC38) and chloroquine-sensitive strain (3D7) of the malaria parasite, Plasmodium falciparum. The presence of the Fc unit was found to enhance both anticancer and antiplasmodial activities of the resultant ferrocenyl Nb compounds with IC50 values in the low to mid micromolar range. Hsp90 inhibitory studies of the ferrocenyl Nb analogues possessing superior activities (2.13a and 2.20c) were also conducted using different yeast strains expressing both human and malarial Hsp90 isoforms: hHsp90a/p and PfHsp90, respectively. The results of Hsp90 inhibitory studies suggested no direct correlation between the observed activities of the analogues and Hsp90 inhibition. However, since the conditions of the assay were not optimised due to time constrains of the project, these observed data remained to be confirmed. , Thesis (MSc) -- Faculty of Science, Chemistry, 2017
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Synthesis, characterisation and evaluation of novel ferrocene-thiazole derivatives as antiplasmodial agents
- Authors: Hakizimana, Emmanuel Victor
- Date: 2017
- Subjects: Plasmodium , Malaria -- Chemotherapy , Plasmodium falciparum , Plasmodium -- Inhibitors , Drug resistance in microorganisms , Thiaszoles
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/5304 , vital:20807
- Description: Malaria is mosquito-transmitted disease which continues to pose threat to humanity, despite the efforts undertaken by the scientific community, government entities and international organizations. The major problem is that Plasmodium species have developed resistance against available drugs. In order to counter this problem, antimalarial drugs that are efficacious and with novel mode of action are of great necessity. Thiazole derivatives, in particular aminomethylthiazole analogues, have been shown to exhibit promising antimalarial activity against Plasmodium falciparum strains. Previous studies reported the hit compound MMV010539, which showed good antimalarial activity against both K1 (CQ and multidrug resistant strains) and NF54 (CQ sensitive strain). In this study, MMV010539 was deemed to be as an attractive compound to generate novel analogues by addition of ferrocenyl organometallic unit. The ferrocene based compounds have shown biological activity; and with ferroquine currently in clinical trials there has been increasing research into identifying new ferrocenyl-containing molecules as potential antimalarial agents. Herein, thiazole ferrocene based molecules 3.22a-e were synthesised in low to good yields. Their structural identities were confirmed using conventional spectroscopic techniques (¹H and ¹³C NMR, FT-IR spectroscopy and mass spectrometry). The cell cytotoxicity assay of all final compounds confirmed that all ferrocene-thiazole blends 3.22a-e were non-toxic against HeLa cell lines. However, the in vitro biological assay revealed that despite the absence of cell cytotoxicity these compounds poorly inhibited the growth of Plasmodium falciparum parasite. As the aim was to expand further the structure-activity relationship (SAR) of MMV010539, this study confirmed the previous findings that there is a limited structural modification that could be accommodated as indicated in Figure 3.3 (Panel C). Moreover, the combination of ferrocenyl moiety and various alkylamines resulted in compounds with poor antiplasmodial potency, further suggesting that the free amine (Panel A, Figure 3.3) is important for activity.
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Synthesis, characterisation and evaluation of novel ferrocene-thiazole derivatives as antiplasmodial agents
- Authors: Hakizimana, Emmanuel Victor
- Date: 2017
- Subjects: Plasmodium , Malaria -- Chemotherapy , Plasmodium falciparum , Plasmodium -- Inhibitors , Drug resistance in microorganisms , Thiaszoles
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/96068 , vital:31232
- Description: Malaria is mosquito-transmitted disease which continues to pose threat to humanity, despite the efforts undertaken by the scientific community, government entities and international organizations. The major problem is that Plasmodium species have developed resistance against available drugs. In order to counter this problem, antimalarial drugs that are efficacious and with novel mode of action are of great necessity. Thiazole derivatives, in particular aminomethylthiazole analogues, have been shown to exhibit promising antimalarial activity against Plasmodium falciparum strains. Previous studies reported the hit compound MMV010539, which showed good antimalarial activity against both K1 (CQ and multidrug resistant strains) and NF54 (CQ sensitive strain). In this study, MMV010539 was deemed to be as an attractive compound to generate novel analogues by addition of ferrocenyl organometallic unit. The ferrocene based compounds have shown biological activity; and with ferroquine currently in clinical trials there has been increasing research into identifying new ferrocenyl-containing molecules as potential antimalarial agents. Herein, thiazole ferrocene based molecules 3.22a-e were synthesised in low to good yields. Their structural identities were confirmed using conventional spectroscopic techniques (¹H and ¹³C NMR, FT-IR spectroscopy and mass spectrometry). The cell cytotoxicity assay of all final compounds confirmed that all ferrocene-thiazole blends 3.22a-e were non-toxic against HeLa cell lines. However, the in vitro biological assay revealed that despite the absence of cell cytotoxicity these compounds poorly inhibited the growth of Plasmodium falciparum parasite. As the aim was to expand further the structure-activity relationship (SAR) of MMV010539, this study confirmed the previous findings that there is a limited structural modification that could be accommodated as indicated in Figure 3.3 (Panel C). Moreover, the combination of ferrocenyl moiety and various alkylamines resulted in compounds with poor antiplasmodial potency, further suggesting that the free amine (Panel A, Figure 3.3) is important for activity.
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