Synthesis and in vitro antimalarial activity
of novel chalcone derivatives
FJ Smit
BSc (UP), Hons BSc (NWU), MSc (NWU)
20926588
Thesis submitted in fulfilment of the requirements for the degree
Philosophiae Doctor
in Pharmaceutical Chemistry
North-West University (Potchefstroom Campus)
Supervisor:
Prof DD N‟Da
May 2014
i
Solemn Declaration
_________________________________________________________________________
I, FRANS JOHANNES SMIT,
herewith declare that the thesis entitled,
SYNTHESIS AND IN VITRO ANTIMALARIAL ACTIVITY OF NOVEL CHALCONE DERIVATIVES
which I herewith submit to the North-West University, Potchefstroom Campus, in compliance with the requirements set for the degree, Philosophiae Doctor, is my own work, has been language edited and has not already been submitted to any other university.
I understand and accept that the copies that are submitted are the property of the University. Signature of student: _____________________________
University number: 20926588
Signed at Potchefstroom this __________ day of __________________________ 2013 Declared before me on this __________ day of __________________________ 2013 Commissioner of Oaths: ______________________________
Declaration by Supervisor / Promoter / Research Director The undersigned declares:
1. that the student attended an approved module(s) of study for the relevant qualification and that the work for the course has been completed, or that work approved by the Senate has been done;
2. that the student has complied with the minimum duration of study as stated in the calendar;
3. the student is hereby granted permission to submit his/her mini-dissertation/dissertation or thesis;
4. that registration/amendment of the title has been approved;
5. that the appointment/amendment of examiners has been finalised;
6. that the student‟s work has been submitted to TurnItIn and a satisfactory report has been obtained; and
7. that all the procedures have been followed according to the Manual for Postgraduate Studies.
Signature Supervisor/Promoter: ___________________________ Date: _______________
Preface
_________________________________________________________________________
This thesis is submitted in an article format in accordance with the General Academic Rules (A.13.7.3) of the North-West University. Three articles, two of which have been submitted, are included in this thesis:
Chapter 3: Article 1
Synthesis, in vitro antimalarial activity and cytotoxicity of novel chalcone-quinoline amides
Chapter 4: Article 2
Synthesis, antimalarial and cytotoxic activity of novel aminoferrocenyl-chalcone amides
Chapter 5: Article 3
Synthesis and biological evaluation of dihydroartemisinyl-chalcone esters
The respective Journals of the submitted articles grant the author the right to include these articles in a thesis. Permission for the Journals is given within their Author's Guides:
Permission from Elsevier: http://www.journals.elsevier.com/bioorganic-and-medicinal-chemistry/
Permission from ScienceDirect: http://www.sciencedirect.com/science/journal/00404020
iii
Acknowledgments
_________________________________________________________________________
I hereby wish to express my appreciation to the following individuals whose guidance enabled me to complete this project successfully:
o Prof DD N‟Da, my Supervisor, for his insight, encouragement and support throughout the entire study.
o Dr JHL Jordaan, for his consistent support and for the collection of MS data.
o Prof JP Petzer, Director of the Department of Pharmaceutical Chemistry, for his support and input into the project.
o Prof J du Plessis, Director of PHARMACEN, for her support, encouragement, input and financial support throughout my study.
o Prof S van Dyk, Director of the School for Pharmacy, for her support. o Dr A Lourens, for her invaluable input in this study.
o Mr A Joubert, for the collection of NMR data.
o The CSIR, for the biological screening of the first and second series.
o Prof L Birkholtz from UP, for her help and guidance, as well as biological screening of series 3.
o Dr HJR Lemmer and Mr N Barnard, for their help with collecting and elucidating DSC/TGA data.
o Dr JR Kriek and Dr V Lates, for their help with electrochemical determination. o The NRF and the North-West University, for financial support.
o All the students at the Department, for their assistance and countless hours of devotion throughout the entire study.
o My friends and family, for their support and love.
Abstract
_________________________________________________________________________
Malaria is endemic in 106 countries worldwide. This disease is caused by a parasite from the genus Plasmodium. Of the five species that infect humans, Plasmodium falciparum is the most virulent, with over three billion people at risk and around 660 000 deaths reported in 2011. Of these deaths, 91% were in the African region, while 86% were children under the age of five. In light of the widespread development of resistance by malaria parasites against the classic antimalarial drugs, such as chloroquine (CQ) and now the established tolerance towards the widely used artemisinins, an immense need exists for identifying and developing new and effective antiplasmodial drugs. In search for such new antimalarial drugs, three chalcone based series of compounds were prepared and investigated during this study.
The first series (Chapter 3) comprised 4-aminoquinolinyl-chalcone amides, which were synthesized through amidation of carboxylic acid-functionalised chalcone with aminoquinolines, using 1,1'-carbonyldiimidazole (CDI) as coupling agent. These compounds were screened alongside CQ against the CQ sensitive (3D7) and CQ resistant (W2) strains of P. falciparum. Cytotoxicity was assessed against the WI-38 cell line. The amide, featuring the 1,6-diaminohexane linker, was found the most active of all these new novel compounds tested. It was found to be as potent as CQ against 3D7, while displaying a two-fold higher activity than CQ against the W2 strain, coupled with good selective antimalarial activity (SI = 435) towards the parasitic cells.
The second series (Chapter 4) consisted of aminoferrocenyl-chalcone amides, synthesized through condensation of a chalcone with an aminoferrocenyl. These compounds were screened against the 3D7, and antifolate- and CQ resistant (FCR3) strains of P. falciparum and cytotoxicity was determined against the WI-38 line. The most active compound of this series was the amide, containing the 1,2-diaminoethane linker, which showed 130- and 42 times less potency than CQ against the 3D7 and W2 strains, respectively.
The third series of antimalarials (Chapter 5) involved dihydroartemisinyl-chalcone esters, synthesized through esterification of chalcones with DHA. These compounds were screened against 3D7 and W2 strains of P. falciparum, while the cytotoxicity was determined against the WI-38 line. Those esters featuring oxygenated aryl rings were three- to four-fold more potent than current clinically used artesunate against both P. falciparum strains. They were also screened in vitro against a panel of three cancer cell lines consisting of TK-10,
UACC-v
62 and MCF-7. Thermogravimetric analysis revealed that the targeted hybrids were all thermally more stable than DHA as a result of the presence of the chalcone moiety in their structures. This could prove beneficial to the high temperature storage conditions that prevail in most malaria endemic countries.
This study resulted in a number of compounds with varying antiplasmodial activity ranges. The compounds in series 3 were overall the most active, due to the incorporation of the highly active dihydroartemisinin pharmacophore. The chalcone moiety, especially, demonstrated a large scope for future development, owing to the ease of synthesis and the relatively low costs involved. The most active compounds of the three series could serve as potential lead compounds in the future development of more effective antimalarial drugs.
Keywords: Plasmodium falciparum, malaria, chalcone, amino quinoline, aminoferrocenyl, dihydroartemisinin
Opsomming
_________________________________________________________________________
Malaria is endemies aan 106 lande regoor die wêreld. Hierdie siekte word deur ‟n parasiet uit die genus Plasmodium veroorsaak. Uit die vyf spesies wat mense kan besmet, is
Plasmodium falciparum die mees virulente, met meer as drie miljard lewens wat in gevaar is,
terwyl ongeveer 660 000 sterftes in 2011 voorgekom het. Uit hierdie gerapporteerde sterftes het 91% in die Afrika-streek voorgekom, waarvan 86% kinders jonger as vyf jaar was. In die lig van die wydverspreide weerstand van die malariaparasiete teen die klassieke antimalariamiddels, soos chlorokien (CQ), en nou die gevestigde toleransie teen die algemeen-gebruikte artemisiniene, bestaan daar ‟n geweldige behoefte om nuwe, doeltreffende anti-malariamiddels te identifiseer en te ontwikkel. In ‟n soektog na nuwe antimalariamiddels is drie chalkoon-gebaseerde reekse verbindings tydens hierdie studie voorberei en ondersoek.
Die eerste reeks middels (Hoofstuk 3) het 4-aminokinoliniel-chalkoon-amiede behels, wat deur die amidasie van karboksielsuur-gefunksionaliseerde chalkoon met aminokinoliene, deur middel van 1,1'-karbonieldiimiedasool as koppelmiddel, gesintetiseer is. Hierdie verbindings is saam met CQ teen die CQ-sensitiewe (3D7) en CQ-weerstandige (W2) stamme van P. falciparum getoets. Sitotoksisiteit is teen die WI-38-sellyn geëvalueer. Die amied met die 1,6-diaminoheksaan-skakel was die aktiefste van almal. Daar is bevind dat dit so effektief soos CQ teen 3D7 was, terwyl dit twee keer hoër aktiwiteit teen die W2-stam getoon het, tesame met goeie selektiewe antimalaria-aktiwiteit (SI = 435) teen die parasitiese selle.
Die tweede reeks (Hoofstuk 4) het uit aminoferroseniel-chalkoon-amiede bestaan, wat deur kondensasie van ‟n chalkoon met „n aminoferroseniel gesintetiseer was. Hierdie verbindings is teen die 3D7-, en antifolaat- en CQ-weerstandige (FCR3) stamme van P. falciparum getoets en sitotoksisiteit is teen die WI-38-lyn bepaal. Die aktiefste verbinding uit hierdie reeks is die amied met die 1,2-diaminoëtaan-skakel, wat 130- en 42 keer minder aktief as CQ teen die 3D7- en W2-stamme, onderskeidelik, was.
Die derde reeks antimalariamiddels (Hoofstuk 5) het dihidroartemisiniel-chalkoon-esters behels, wat deur die verestering van chalkone met DHA gesintetiseer was. Hierdie verbindings is teen die 3D7- en W2-stamme van Plasmodium falciparum getoets, terwyl die sitotoksisiteit teen die WI-38-sellyn geëvalueer is. Daardie esters met geoksigeneerde
vii
arielringe is drie tot vier keer meer aktief as die artesunaat wat tans klinies teen albei P.
falciparum-stamme gebruik word. Hierdie verbindings is ook teen drie kanker sel-lyne,
opgemaak uit TK-10, UACC-62 and MCF-7 kanker selle, geëvalueer. Termogravimetriese ontleding het getoon dat al die geteikende hibriede, as gevolg van die aanwesigheid van die chalkoon-gedeelte in hulle strukture, termies meer stabiel as DHA was. Dit mag tot voordeel van die hoë temperatuurstoorkondisies, soos wat in die meeste malaria-endemiese lande heers, bevind word.
Hierdie studie het tot ‟n aantal verbindings met wisselende aktiwiteitsvlakke aanleiding gegee. Die verbindings in reeks 3 was oorkoepelend die aktiefste, weens die inkorporasie van die uiters aktiewe dihidroartemesinien-farmakofoor. Die chalkoon-komponent, veral, het geweldige potensiaal vir toekomstige ontwikkeling getoon, as gevolg van die gemak waarmee dit gesintetiseer word en die relatief lae koste betrokke. Die aktiefste verbindings uit al die drie reekse kan as potensiële leidraadverbindings vir die ontwikkeling van doeltreffender antimalariamiddels in die toekoms dien.
Sleutelwoorde: Plasmodium falciparum, malaria, chalkoon, aminokinolien, aminoferroseniel, dihidroartemesinien
List of Contents
_________________________________________________________________________ Solemn Declaration ... i Preface... ... ii Acknowledgments ... iii Abstract... ... iv Opsomming... ... viList of Contents ... ...viii
List of Figures.. ... xv
List of Tables and Schemes ... xvii
List of Abbreviations ... xviii
Chapter 1: Introduction and Problem Statement ... 1
1.1. Background ... 1
1.2 Aim ... 6
1.3 Objectives... 6
Chapter 2: Literature review ... 7
2.1 Introduction ... 7
2.2 Life cycle and pathogenesis ... 8
2.3 Haemoglobin degradation ... 10
2.4 Signs and symptoms ... 11
2.5 Diagnosis... 13
2.6 Control and prevention ... 14
2.7 Chemotherapy ... 16
2.7.1 Antifolates and hydroxynaphthoquinones ... 16
2.7.2 Antimicrobials ... 20
2.7.3 8-Aminoquinolines ... 21
2.7.4 Aryl-amino alcohols ... 22
ix
2.7.6 Artemisinin and derivatives ... 26
2.7.7 Chalcone compounds ... 29
2.7.8 Hybrid drug theory ... 31
2.7.9 Chalcone based hybrids ... 32
Chapter 3: Synthesis, in vitro antimalarial activity and cytotoxicity of novel chalcone-quinoline amides - Article 1 ... ..37
Abstract...40
1. Introduction...40
2. Materials and methods...41
2.1 Materials...41
2.2 General procedures...41
2.3 Biological evaluation...42
2.3.1 In vitro antimalarial assay...42
2.3.2 In vitro cytotoxicity...42 2.4 Synthesis...42 2.4.1 4-Amino-7-chloroquinolines, 1–9...42 2.4.1.1. N-(2-Aminoethyl)-7-chloroquinolin-4-amine, 1...42 2.4.1.2. N-(3-Aminopropyl)-7-chloroquinolin-4-amine, 2...42 2.4.1.3. N-(4-Aminobutyl)-7-chloroquinolin-4-amine, 3...42 2.4.1.4. N-(2-Aminopropyl)-7-chloroquinolin-4-amine, 4...43 2.4.1.5. N-(6-Aminohexyl)-7-chloroquinolin-4-amine, 5...43 2.4.1.6. {3-[(7-Chloroquinolin-4-yl)amino]propyl}(methyl)amine, 6...43 2.4.1.7. N-{2-[2-(2-Aminoethoxy)ethoxy]ethyl}-7-chloroquinolin-4-amine, 7...44 2.4.1.8. (3-Aminopropyl)({3-[(7-chloroquinolin-4-yl)amino] propyl})methylamine, 8...44 2.4.1.9. 7-Chloro-4-(piperazin-1-yl)quinoline, 9...44 2.4.2. 4-[(1E)-3-(5-Methylfuran-2-yl)-3-oxoprop-1-en-1-yl]benzoic acid, 10...44 2.4.3. 4-Aminoquinolinyl-chalcone amides, 11-19...44 2.4.3.1 N-{2-[(7-Chloroquinolin-4-yl)amino]ethyl}-4-[(1E)-3-(5-methylfuran-2-yl)-3-oxoprop-1-en-1-yl]benzamide, 11...44 2.4.3.2. N-{3-[(7-Chloroquinolin-4-yl)amino]propyl}-4-[(1E)-3-(5-methylfuran-2-yl)-3-oxoprop-1-en-1-yl]benzamide,12...44 2.4.3.3. N-{4-[(7-Chloroquinolin-4-yl)amino]butyl}-4-[(1E)-3-(5-methylfuran-2-yl)-3-oxoprop-1-en-1-yl]benzamide, 13...45 2.4.3.4. N-{1-[(7-Chloroquinolin-4-yl)amino]propan-2-yl}-4-[(1E)-3-(5-methylfuran-2-yl)-3-oxoprop-1-en-1-yl]benzamide, 14...45
2.4.3.5. N-{6-[(7-Chloroquinolin-4-yl)amino]hexyl}-4-[(1E)-3-(5-methylfuran-2-yl)-3-oxoprop-1-en-1-yl]benzamide, 15...45 2.4.3.6. N-{3-[(7-Chloroquinolin-4-yl)amino]propyl}-N-methyl- 4-[(1E)-3-(5-methylfuran-2-yl)-3-oxoprop-1-en-1-yl]benzamide, 16...45 2.4.3.7. N-[2-(2-{2-[(7-Chloroquinolin-4-yl)amino]ethoxy}ethoxy)ethyl]-4-[(1E)-3-(5-methylfuran-2-yl)-3-oxoprop-1-en-1-yl]benzamide, 17...45 2.4.3.8. N-[3-({3-[(7-Chloroquinolin-4-yl)amino]propyl} (methyl)amino)propyl]-4-[(1E)-3-(5-methylfuran-2-yl)-3-oxo- prop-1-en-1-yl]benzamide, 18...45 2.4.3.9. (2E)-3-(4-{[4-(7-Chloroquinolin-4-yl)piperazin-1-yl]carbonyl}phenyl)-1-(5-methylfuran-2-yl)prop-2-en-1-one, 19...46 2.4.4. Chalconyl amides, 20–22...46 2.4.4.1. 4-[(1E)-3-(5-Methylfuran-2-yl)-3-oxoprop-1-en-1- yl]benzamide, 20...46 2.4.4.2. N-Butyl-4-[(1E)-3-(5-methylfuran-2-yl)-3-oxoprop-1- en-1-yl]-benzamide, 21...46 2.4.4.3. (2E)-1-(5-Methylfuran-2-yl)-3-{4-[(morpholin-4-yl)carbonyl]-phenyl}prop-2-en-1-one, 22...46 3. Results...46 3.1. Chemistry...46 3.2. Physicochemical properties...47
3.3. In vitro antimalarial activity and cytotoxicity...47
4. Discussion...48
4.1. Chemistry...48
4.2. Physicochemical properties...48
4.3. In vitro antimalarial activity and cytotoxicity...49
5. Conclusion...49
6. Disclaimer...50
References and notes...50
Chapter 4: Synthesis, antimalarial activity and cytotoxicity of novel aminoferrocenyl-chalcone amides - Article 2 ... .51
Abstract ... ...53
1. Introduction ... 54
2. Materials and Methods ... 56
2.1 Materials ... 56
2.2 General procedures ... 56
2.3 Biological testing... 57
xi
2.3.2 In vitro cytotoxicity assay ... 58
2.4 Synthesis ... 58
2.4.1 Condensation of diamines with ferrocene carboxaldehyde ... 58
2.4.1.1. N-ferrocenyl-1,2-diaminoethane, 1... 59 2.4.1.2. N-ferrocenyl-1,3-diaminopropane, 2 ... 59 2.4.1.3. N-ferrocenyl-1,4-diaminobutane, 3... 60 2.4.1.4. N-ferrocenyl-2-aminoethylpiperazine, 4 ... 60 2.4.1.5. N-ferrocenyl-1,2-diaminopropane, 5 ... 60 2.4.1.6. N-ferrocenyl-N‟-methyl-1,3-diaminopropane, 6 ... 60 2.4.1.7. N-ferrocenyl-2,2'-(ethylenedioxy)bis(ethylamine), 7 ... 61 2.4.1.8. N-ferrocenyl-N-(3-aminopropyl)-N-methylpropane-1,3-diamine, 8... 61 2.4.1.9. N-ferrocenyl-piperazine, 9 ... 61 2.4.2 4-[(1E)-3-(5-methylfuran-2-yl)-3-oxoprop-1-en-1-yl]benzoic acid ... 62
2.4.3 Condensation of chalcone with aminoferrocenyl ... 64
2.4.3.1 N-[2-(ferrocenylamino)ethyl]-4-[(1E)-3-(5-methylfuran-2-yl)-3-oxoprop-1-en-1-yl]benzamido oxalate, 11 ... 64 2.4.3.2 N-[3-(ferrocenylamino)propyl]-4-[(1E)-3-(5-methylfuran-2-yl)-3-oxoprop-1-en-1-yl]benzamido oxalate, 12 ... 64 2.4.3.3 N-[4-(ferrocenylamino)butyl]-4-[(1E)-3-(5-methylfuran-2-yl)-3-oxoprop-1-en-1-yl]benzamido oxalate, 13 ... 65 2.4.3.4 (2E)-3-[4-({4-[2-(ferrocenylamino)ethyl]piperazin-1-yl}carbonyl)phenyl]-1-(5-methylfuran-2-yl)prop-2-en-1-one oxalate, 14 ... 65 2.4.3.5 N-[1-(ferrocenylamino)propan-2-yl]-4-[(1E)-3-(5-methylfuran-2-yl)-3-oxoprop-1-en-1-yl]benzamido oxalate, 15 ... 66 2.4.3.6 N-[3-(ferrocenylamino)propyl]-N-methyl-4-[(1E)-3-(5-methylfuran-2-yl)-3-oxoprop-1-en-1-yl]benzamido oxalate, 16 ... 66 2.4.3.7 N-(2-{2-[2-(ferrocenylamino)ethoxy]ethoxy}ethyl)-4-[(1E)-3-(5-methylfuran-2-yl)-3-oxoprop-1-en-1-yl]benzamido oxalate, 17 ... 66 2.4.3.8 N-(3-{[3-(ferrocenylamino)propyl](methyl)amino}propyl)-4-[(1E)-3-(5-methylfuran-2-yl)-3-oxoprop-1-en-1-yl]benzamido oxalate, 18 ... 67
2.4.3.9
(2E)-3-{4-[(4-ferrocenylpiperazin-1-yl)carbonyl]phenyl}-1-(5-methylfuran-2-yl)prop-2-en-1-one oxalate, 19 ... 67
3. Results ... 68
3.1 Chemistry ... 68
3.2 Reduction potential and physicochemical properties ... 68
3.3 In vitro antimalarial activity and cytotoxicity ... 69
4. Discussion ... 71
4.1 Chemistry ... 71
4.2 Reduction potential and physicochemical properties ... 72
4.3 In vitro antimalarial activity and cytotoxicity ... 73
5. Conclusion... 75
References ... 77
Chapter 5: Synthesis and biological evaluation of dihydroartemisinyl-chalcone esters - Article 3 ... 79 Abstract ... 81 1. Introduction ... 82 2. Results ... 84 2.1 Chemistry ... 84 2.2 Physiochemical properties ... 84
2.3 In vitro antimalarial activity and cytotoxicity ... 86
2.4 In vitro antitumor activity ... 89
3. Discussion ... 91
3.1 Chemistry ... 91
3.2 Physicochemical properties ... 93
3.3 In vitro antimalarial and cytotoxicity ... 95
3.4 In vitro antitumor activity ... 96
3.5 Selective antiplasmodial activity of hybrids ... 97
4. Conclusion... 97
5. Materials and Methods ... 98
xiii
5.2 General procedures ... 98
5.3 Physicochemical properties ... 99
5.4 Biological evaluation ... 100
5.4.1 In vitro antimalarial assay ... 100
5.4.2 In vitro cytotoxicity assay ... 100
5.4.3 In vitro anticancer assay ... 101
5.5 Synthesis ... 102 5.5.1 Claisen-Schmidt condensation, 1 - 6 ... 102 5.5.1.1. 4-[(1E)-3-(5-methylfuran-2-yl)-3-oxoprop-1-en-1-yl]benzoic acid, 1... 102 5.5.1.2. 4-[(1E)-3-oxo-3-phenylprop-1-en-1-yl]benzoic acid, 2 ... 102 5.5.1.3. 4-[(1E)-3-(3-methoxy-4-nitrophenyl)-3-oxoprop-1-en-1-yl]benzoic acid, 3 ... 103 5.5.1.4. 4-[(1E)-3-(3,4-dimethoxyphenyl)-3-oxoprop-1-en-1-yl]benzoic acid, 4 ... 103 5.5.1.5. 4-[(1E)-3-(2,4-dimethoxyphenyl)-3-oxoprop-1-en-1-yl]benzoic acid, 5 ... 103 5.5.1.6. 4-[(1E)-3-oxo-3-(2,3,4-trichlorophenyl)prop-1-en-1-yl]benzoic acid, 6 ... 104
5.5.2 Esterification of chalcone with dihydroartemisinin ... 104
5.5.2.1. 10α-dihydroartemisinyl-4-[(1E)-3-(5-methylfuran-2-yl)-3-oxoprop-1-en-1-yl]benzoate, 7 ... 106 5.5.2.2. 10-dihydroartemisinyl-4-[(1E)-3-oxo-3-phenylprop-1-en-1-yl]benzoate, 8 ... 106 5.5.2.3. 10-dihydroartemisinyl-4-[(1E)-3-(3-methoxy-4-nitrophenyl)-3-oxoprop-1-en-1-yl]benzoate, 9 ... 107 5.5.2.4. 10-dihydroartemisinyl-4-[(1E)-3-(3,4-dimethoxyphenyl)-3-oxoprop-1-en-1-yl]benzoate, 10 ... 107 5.5.2.5. 10-dihydroartemisinyl-4-[(1E)-3-(2,4-dimethoxyphenyl)-3-oxoprop-1-en-1-yl]benzoate, 11 ... 108 5.5.2.6. 10β-dihydroartemisinyl-4-[(1E)-3-oxo-3-(2,3,4-trichlorophenyl)prop-1-en-1-yl]benzoate, 12 ... 108 References ... 110
Chapter 6: Summary and Conclusion ... 112
References... ... 117
Addendum B: Analytical data for Chapter 4 ... 187
xv
List of Figures
_______________________________________________________________________
Figure 1.1: Global prevalence of malaria in 2010 ... 1
Figure 1.2: Artemisinin and its derivatives. ... 2
Figure 1.3: Cysteine protease inhibitor E64 (A), general structure of a chalcone (B) and Licochalcone A (C). ... 3
Figure 1.4: Clinically used chloroquine (CQ). ... 4
Figure 1.5: General structure of quinolinyl-chalcones ... 5
Figure 2.1: The complex life cycle of the Plasmodium sp. ... 9
Figure 2.2: Animation showing how the Plasmodium parasite acquire haemoglobin... 10
Figure 2.3: Haemoglobin degradation in the digestive vacuole ... 11
Figure 2.4: Common symptoms and organs affected by malaria. ... 12
Figure 2.5: Biosynthetic pathway of Tetrahydrofolate. ... 17
Figure 2.6: Sub -class I antifolates: sulfadoxine (1) and dapsone (2). ... 18
Figure 2.7: Sub-class II antifolates: pyrimethamine (3), proguanil (4) and its active metabolite cycloguanil (5). ... 18
Figure 2.8: Chemical structure of the hydroxynaphthoquinone atovaquone (6)... 19
Figure 2.9: Chemical structures of the antibiotics doxycycline (7) and clindamycin (8). ... 20
Figure 2.10: Chemical structure of primaquine (9). ... 21
Figure 2.11: Chemical structures of quinine (10), quinidine (11), mefloquine (12) and halofantrine (13). ... 22
Figure 2.12: Chemical structures of 4-aminoquinolines: chloroquine (CQ, 14), amodiaquine (15) and piperaquine (16). ... 25
Figure 2.13: Illustration of the Pfcrt protein that allows the outward movement of CQ ... 26
Figure 2.14: Clinically used artemisinin (17), dihydroartemisinin (18), artemether (19), arteether (20) and artesunate (21). ... 27
Figure 2.15: Cysteine protease inhibitor E64 (22), general structure of a chalcone (23) and Licochalcone A (24). ... 30
Figure 2.16: Chemical structure of 1E-(2,5-dichlorophenyl)-3(4-quinolinyl)-2-propen-1
-one (25)... ... 30
Figure 2.17: Three binding possibilities of hybrid compounds. ... 32
Figure 2.18: General structure of quinolinyl-chalcone based hybrids (26) synthesized by Sharma et al. (2009). ... 33
Figure 2.19: General structure of the keto-enamine chalcone-chloroquine based hybrid (27) ... 34
Figure 2.20: Chemical structure of ferroquine (28). ... 35
Figure 2.21: General structures of ferrocenyl-chalcones. ... 35
Figure 2.22: General structure of endoperoxide-chalcone based hybrids (31) ... 36
Figure 2.23: General structure of dihydroartemisinin-chalcone based hybrids. ... 36
Chapter 3: Figure 1: General structure of a chalcone, cysteine protease inhibitor E64 and licochalcone A...41
Figure 2: General structures of quinolinyl-chalcones synthesized by Sharma et al. (A) and Sashidhara et al. (B)...41
Chapter 4: Figure 1: Chemical structures of ferroquine (FQ), chloroquine (CQ) and Licochalcone A.55 Figure 2: General structure of targeted compounds 11 – 18, indicating the same chemical environment. ... 73
Chapter 5: Figure 1: Clinically used artemisinin and its derivatives. ... 82
Figure 2: General structure of a chalcone and Licochalcone A. ... 83
Figure 3: The percentage proliferation of chalcones 1, 4 and 5, together with DHA and the molar combinations thereof... 88
xvii
List of Tables and Schemes
_________________________________________________________________________
Article 1:
Scheme 1: Multi-step synthesis of 4-aminoquinolinyl-chalcone amides 11–19...43
Scheme 2: Synthesis of chalconyl amides 20 – 22. ... 46
Table 1: Calculated physicochemical properties of compounds 10 - 22 and CQ ... 47
Table 2: Antimalarial activity and cytotoxicity of screened amide compounds ...47
Article 2: Scheme 1: Multi-step synthesis of aminoferrocenyl-chalcone amides 11 – 19. ... 63
Table 1: Electrochemical potential of synthesized compounds ... 68
Table 2: Calculated ADMET properties of synthesized compounds ... 69
Table 3: In vitro antimalarial activity and cytotoxicity of screened compounds ... 70
Article 3: Figure 1: Clinically used artemisinin and its derivatives. ... 82
Figure 2: General structure of a chalcone and licochalcone A. ... 83
Table 1: Calculated physicochemical properties of compounds 1 - 12, CQ, DHA and AS85 Table 2: Antimalarial activity and cytotoxicity of screened compounds ... 87
Figure 3: The percentage cell proliferation with the addition of chalcones 1, 4 and 5, DHA and the molar combinations thereof, respectively. ... 88
Table 3: Antitumor activity of screened compounds... 90
Table 4: Selective antiplasmodial activity versus anticancer activity of synthesized compounds ... 91
List of Abbreviations
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ACT Artemisinin based combined therapy ARF Acute renal failure
AS Artesunate
13C NMR Carbon NMR
CBV Cerebral blood volume
CM Cerebral malaria
COSY Correlation spectroscopy
CQ Chloroquine
CQR Chloroquine resistant CQS Chloroquine sensitive
Cyt bc1 Cytochrome bc1
DDT Dichlorodiphenyltrichloroethane
DEPT Distortionless enhancement by polarization transfer
DHA Dihydroartemisinin
DHF Dihydrofolate
DHFR Dihydrofolate reductase
dhfr-ts Dihydrofolate reductase-thymidylate synthase DHPS Dihydropteroate synthase
DNA Deoxyribonucleic acid
DSC Differential scanning calorimetry FDA Food and Drug Administration
G6PD Glucose-6-phosphate dehydrogenase
1H NMR Proton NMR
HRMS High resolution mass spectrometry HSQC Heteronuclear single quantum coherence IC50 50% inhibitory concentration
IL-4 Interleukin-4
IPT Intermittent preventative treatment
IR Infrared spectroscopy
IRS Indoor residual spraying
ITN Insecticide treated nets
NADPH Nicotinamide adenine dinucleotide phosphate NMR Nuclear magnetic resonance
xix npRBCs Non-parasitized red blood cells
PABA Para-aminobenzoic acid
Pfcrt Plasmodium falciparum chloroquine resistance transporter
pfmdr1 gene Plasmodium falciparum multi-drug resistant gene
Pgh1 efflux pump P-glycoprotein efflux pump pRBCs Parasitized red blood cells
RBM Roll Back Malaria
RDTs Rapid diagnostic tests ROS Reactive oxygen species SCD Sickle cell disease SCT Sickle cell trait
SERCA Sarcoplasmic/endoplasmic reticulum calcium ATPase
SP Sulfadoxine/pyrimethamine
TGA Thermogravemetric analysis
THF Tetrahydrofolate
