Repurposing a polymer precursor scaffold for medicinal application: Synthesis, characterization and biological evaluation of ferrocenyl 1,3-benzoxazine derivatives as potential antiprotozoal and anticancer agents
- Authors: Mbaba, Mziyanda
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/164502 , vital:41124 , DOI 10.21504/10962/164502
- Description: The benzoxazines are a prominent class of heterocyclic compounds that possess a multitude of properties. To this end, benzoxazine derivatives have been used as versatile compounds for various utilities ranging from biological applications to the fabrication of polymers. Particularly, the 1,3-benzoxazine scaffold has featured in several bioactive compounds showing antimalarial, anticancer and antibacterial activities. Traditionally, it has been employed as a substrate in the synthesis of polymers with appealing physical and chemical properties. Due to the increasing interest in the polymer application of 1,3-benzoxazines, research of the 1,3-benzoxazine motif for polymer synthesis has been prioritized over other applications including its medicinal potential. The continuous development of resistance to clinical anticancer and antimalarial drugs has necessitated the need for the search of innovative bioactive compounds as potential alternative medicinal agents. To address this, the field of medicinal chemistry is adapting new approaches to counter resistance by incorporating nonconventional chemical moieties such as organometallic complexes, like ferrocene, into bioactive chemical motifs to serve as novel compounds with medicinal benefits. Incorporation of ferrocene into known bioactive chemical moieties has been shown to impart beneficial biological effects into the resultant compounds, which include the introduction of novel, and sometimes varied, mechanistic modalities and enhanced potency. Presented with the benefits of this strategy, the current work aims to design and evaluate the pharmaceutical capacity of novel derivatives containing 1,3-benzoxazine scaffold (traditionally applied in polymer synthesis) hybridized with the organometallic ferrocene unit as bioactive agents. Using a combination of expedient synthetic procedures such as the Burke three-component Mannich-type condensation, Vilsmeier-Haack formylation and reductive amination, four series of ferrocenyl 1,3-benzoxazine derivatives were synthesized and their structures confirmed by common spectroscopic techniques: nuclear magnetic resonance (NMR), infrared spectroscopy (IR) and high-resolution mass spectrometry (HRMS). The target compounds were evaluated in vitro for potential antimalarial and anticancer activities against strains of the malaria parasite (Plasmodium falciparum 3D7 and Dd2) and the triple-negative breast cancer cell line HCC70. Compounds exhibited higher potency towards the Plasmodium falciparum strains with IC50 values in the low and sub-micromolar range in comparison to the breast cancer cell line against for which mid-molar activities were observed. To gain insight into the possible mode of action of ferrocenyl 1,3-benzoxazines, representative compounds showing most efficacy from each series were assessed for DNA binding affinity by employing UV-Vis and fluorescence DNA titration experiments. The selected compounds were found to interact with the DNA by binding to the minor groove, and these findings were confirmed by in silico ligand docking studies using a B-DNA structure as the receptor. Compound 3.16c (IC50: 0.261 μM [3D7], 0.599 μM [Dd2], 11.0 μM [HCC70]), which emerged as the most promising compound, was found to induce DNA damage in HCC70 cancer cells when investigated for effects of DNA interaction. Additionally, compound 3.16c displayed a higher binding constant (Kb) against DNA isolated from 3D7 Plasmodium falciparum trophozoites (Kb = 1.88×106 M-1) than the mammalian DNA (Kb = 6.33×104 M-1) from calf thymus, thus explaining the preferred selectivity of the compounds for the malaria parasite. Moreover, the investigated compounds demonstrated binding affinity for synthetic hemozoin, β-hematin. Collectively, these data suggest that the compounds possess a dual mode of action for antimalarial activity involving DNA interaction and hemozoin inhibition. , Thesis (PhD) -- Faculty of Science, Chemistry, 2020
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- Date Issued: 2020
Repurposing a polymer precursor: Synthesis and in vitro medicinal potential of ferrocenyl 1, 3-benzoxazine derivatives
- Authors: Mbaba, Mziyanda , Dingle, Laura M K , Cash, Devon , de la Mare, Jo-Anne , Laming, Dustin , Taylor, Dale , Hoppe, Heinrich C , Edkins, Adrienne L , Khanye, Setshaba D
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/165395 , vital:41240 , https://doi.org/10.1016/j.ejmech.2019.111924
- Description: Cancer and malaria remain relevant pathologies in modern medicinal chemistry endeavours. This is compounded by the threat of development of resistance to existing clinical drugs in use as first-line option for treatment of these diseases. To counter this threat, strategies such as drug repurposing and hybridization are constantly adapted in contemporary drug discovery for the expansion of the drug arsenal and generation of novel chemotypes with potential to avert or delay resistance. In the present study, a polymer precursor scaffold, 1,3-benzoxazine, has been repurposed by incorporation of an organometallic ferrocene unit to produce a novel class of compounds showing in vitro biological activity against breast cancer, malaria and trypanosomiasis.
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- Date Issued: 2020
The in vitro antiplasmodial and antiproliferative activity of new ferrocene-based α-aminocresols targeting hemozoin inhibition and DNA interaction:
- Authors: Mbaba, Mziyanda , Dingle, Laura M K , Swart, Tarryn , Cash, Devon , Laming, Dustin , de la Mare, Jo-Anne , Taylor, Dale , Hoppe, Heinrich C , Biot, Christophe , Edkins, Adrienne L , Khanye, Setshaba D
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149347 , vital:38827 , https://0-doi.org.wam.seals.ac.za/10.1002/cbic.202000132
- Description: Compounds incorporating ferrocene in a aminocresol scaffold showed antiplasmodial and anticancer activity. SAR studies revealed that an OH group and rotatable C–NH bond are vital for biological activity, with spectrophotometric techniques and docking simulations suggesting a dual mode of action involving hemozoin inhibition and DNA interaction. Targeting multiple pathways could delay the development of clinical resistance.
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- Date Issued: 2020
Ferrocenyl and organic novobiocin derivatives: synthesis and their in vitro biological activity
- Authors: Mbaba, Mziyanda , Mabhula, Amanda N , Boel, Natasha , Edkins, Adrienne L , Isaacs, Michelle , Hoppe, Heinrich C , Khanye, Setshaba D
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/66189 , vital:28914 , https://doi.org/10.1016/j.jinorgbio.2017.04.014
- Description: publisher version , A focused series of novobiocin derivatives containing a ferrocene unit together with their corresponding organic novobiocin analogues have been synthesized in modest to good yields. These compounds were screened for biological activity against a chloroquine-sensitive strain of Plasmodium falciparum (3D7) and human breast cancer cell line (HCC38). With the exception of compounds 5c and 5d, the general trend observed is that incorporation of the ferrocene moiety into novobiocin scaffold resulted in compounds 6a–d/6f showing enhanced activity compared to organic analogues 5a–b and 5e–f.
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- Date Issued: 2017
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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- Date Issued: 2017
Novobiocin–ferrocene conjugates possessing anticancer and antiplasmodial activity independent of HSP90 inhibition.
- Authors: Mbaba, Mziyanda , de la Mare, Jo-Anne , Sterrenberg, Jason N , Kajewole, Deborah , Maharaj, Shantal , Edkins, Adrienne L , Isaacs, Michelle , Hoppe, Heinrich C , Khanye, Setshaba D
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/122858 , vital:35359 , https://doi.org/10.1007/s00775-018-1634-9
- Description: A series of tailored novobiocin–ferrocene conjugates was prepared in moderate yields and investigated for in vitro anticancer and antiplasmodial activity against the MDA-MB-231 breast cancer line and Plasmodium falciparum 3D7 strain, respectively. While the target compounds displayed moderate anticancer activity against the breast cancer cell line with IC50 values in the mid-micromolar range, compounds 10a–c displayed promising antiplasmodial activity as low as 0.889 µM. Furthermore, the most promising compounds were tested for inhibitory effects against a postulated target, heat shock protein 90 (Hsp90).
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