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Wu Y, Wu RWK, Cheu KW, Williams ID, Krishna S, Slavic K, Gravett AM, Liu WM, Wong HN, Haynes RK. Methylene Homologues of Artemisone: An Unexpected Structure-Activity Relationship and a Possible Implication for the Design of C10-Substituted Artemisinins. ChemMedChem 2016; 11:1469-79. [PMID: 27273875 DOI: 10.1002/cmdc.201600011] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Revised: 05/13/2016] [Indexed: 11/12/2022]
Abstract
We sought to establish if methylene homologues of artemisone are biologically more active and more stable than artemisone. The analogy is drawn with the conversion of natural O- and N-glycosides into more stable C-glycosides that may possess enhanced biological activities and stabilities. Dihydroartemisinin was converted into 10β-cyano-10-deoxyartemisinin that was hydrolyzed to the α-primary amide. Reduction of the β-cyanide and the α-amide provided the respective methylamine epimers that upon treatment with divinyl sulfone gave the β- and α-methylene homologues, respectively, of artemisone. Surprisingly, the compounds were less active in vitro than artemisone against P. falciparum and displayed no appreciable activity against A549, HCT116, and MCF7 tumor cell lines. This loss in activity may be rationalized in terms of one model for the mechanism of action of artemisinins, namely the cofactor model, wherein the presence of a leaving group at C10 assists in driving hydride transfer from reduced flavin cofactors to the peroxide during perturbation of intracellular redox homeostasis by artemisinins. It is noted that the carba analogue of artemether is less active in vitro than the O-glycoside parent toward P. falciparum, although extrapolation of such activity differences to other artemisinins at this stage is not possible. However, literature data coupled with the leaving group rationale suggest that artemisinins bearing an amino group attached directly to C10 are optimal compounds.
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Affiliation(s)
- Yuet Wu
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P.R. China
| | - Ronald Wai Kung Wu
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P.R. China
| | - Kwan Wing Cheu
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P.R. China
| | - Ian D Williams
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P.R. China
| | - Sanjeev Krishna
- Centre for Infection, Division of Cellular and Molecular Medicine, St. George's Hospital, University of London, SW17 0RE, UK
| | - Ksenija Slavic
- Centre for Infection, Division of Cellular and Molecular Medicine, St. George's Hospital, University of London, SW17 0RE, UK
| | - Andrew M Gravett
- Department of Oncology, Division of Cellular and Molecular Medicine, St. George's Hospital, University of London, Jenner Wing, London, SW17 0RE, UK
| | - Wai M Liu
- Department of Oncology, Division of Cellular and Molecular Medicine, St. George's Hospital, University of London, Jenner Wing, London, SW17 0RE, UK
| | - Ho Ning Wong
- Centre of Excellence for Pharmaceutical Sciences, Faculty of Health Sciences, North-West University, Potchefstroom, 2520, South Africa.,Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P.R. China
| | - Richard K Haynes
- Centre of Excellence for Pharmaceutical Sciences, Faculty of Health Sciences, North-West University, Potchefstroom, 2520, South Africa. , .,Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P.R. China. ,
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Griesbeck AG, Schlundt V, Neudörfl JM. Functionalized polar 1,2,4-trioxanes as building blocks by singlet oxygenation of 4-hydroxy tiglic acid using the solvent deuterium isotope trick. RSC Adv 2013. [DOI: 10.1039/c3ra40555a] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
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Haynes RK, Cheu KW, Chan HW, Wong HN, Li KY, Tang MMK, Chen MJ, Guo ZF, Guo ZH, Sinniah K, Witte AB, Coghi P, Monti D. Interactions between artemisinins and other antimalarial drugs in relation to the cofactor model--a unifying proposal for drug action. ChemMedChem 2012; 7:2204-26. [PMID: 23112085 DOI: 10.1002/cmdc.201200383] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Revised: 09/30/2012] [Indexed: 01/14/2023]
Abstract
Artemisinins are proposed to act in the malaria parasite cytosol by oxidizing dihydroflavin cofactors of redox-active flavoenzymes, and under aerobic conditions by inducing their autoxidation. Perturbation of redox homeostasis coupled with the generation of reactive oxygen species (ROS) ensues. Ascorbic acid-methylene blue (MB), N-benzyl-1,4-dihydronicotinamide (BNAH)-MB, BNAH-lumiflavine, BNAH-riboflavin (RF), and NADPH-FAD-E. coli flavin reductase (Fre) systems at pH 7.4 generate leucomethylene blue (LMB) and reduced flavins that are rapidly oxidized in situ by artemisinins. These oxidations are inhibited by the 4-aminoquinolines piperaquine (PPQ), chloroquine (CQ), and others. In contrast, the arylmethanols lumefantrine, mefloquine (MFQ), and quinine (QN) have little or no effect. Inhibition correlates with the antagonism exerted by 4-aminoquinolines on the antimalarial activities of MB, RF, and artemisinins. Lack of inhibition correlates with the additivity/synergism between the arylmethanols and artemisinins. We propose association via π complex formation between the 4-aminoquinolines and LMB or the dihydroflavins; this hinders hydride transfer from the reduced conjugates to the artemisinins. The arylmethanols have a decreased tendency to form π complexes, and so exert no effect. The parallel between chemical reactivity and antagonism or additivity/synergism draws attention to the mechanism of action of all drugs described herein. CQ and QN inhibit the formation of hemozoin in the parasite digestive vacuole (DV). The buildup of heme-Fe(III) results in an enhanced efflux from the DV into the cytosol. In addition, the lipophilic heme-Fe(III) complexes of CQ and QN that form in the DV are proposed to diffuse across the DV membrane. At the higher pH of the cytosol, the complexes decompose to liberate heme-Fe(III) . The quinoline or arylmethanol reenters the DV, and so transfers more heme-Fe(III) out of the DV. In this way, the 4-aminoquinolines and arylmethanols exert antimalarial activities by enhancing heme-Fe(III) and thence free Fe(III) concentrations in the cytosol. The iron species enter into redox cycles through reduction of Fe(III) to Fe(II) largely mediated by reduced flavin cofactors and likely also by NAD(P)H-Fre. Generation of ROS through oxidation of Fe(II) by oxygen will also result. The cytotoxicities of artemisinins are thereby reinforced by the iron. Other aspects of drug action are emphasized. In the cytosol or DV, association by π complex formation between pairs of lipophilic drugs must adversely influence the pharmacokinetics of each drug. This explains the antagonism between PPQ and MFQ, for example. The basis for the antimalarial activity of RF mirrors that of MB, wherein it participates in redox cycling that involves flavoenzymes or Fre, resulting in attrition of NAD(P)H. The generation of ROS by artemisinins and ensuing Fenton chemistry accommodate the ability of artemisinins to induce membrane damage and to affect the parasite SERCA PfATP6 Ca(2+) transporter. Thus, the effect exerted by artemisinins is more likely a downstream event involving ROS that will also be modulated by mutations in PfATP6. Such mutations attenuate, but cannot abrogate, antimalarial activities of artemisinins. Overall, parasite resistance to artemisinins arises through enhancement of antioxidant defense mechanisms.
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Affiliation(s)
- Richard K Haynes
- Department of Chemistry, Institute of Molecular Technology for Drug Discovery and Synthesis, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, PR China.
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Haynes RK, Cheu KW, Li KY, Tang MMK, Wong HN, Chen MJ, Guo ZF, Guo ZH, Coghi P, Monti D. A partial convergence in action of methylene blue and artemisinins: antagonism with chloroquine, a reversal with verapamil, and an insight into the antimalarial activity of chloroquine. ChemMedChem 2011; 6:1603-15. [PMID: 21994127 DOI: 10.1002/cmdc.201100184] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2011] [Revised: 06/13/2011] [Indexed: 12/19/2022]
Abstract
Artemisinins rapidly oxidize leucomethylene blue (LMB) to methylene blue (MB); they also oxidize dihydroflavins such as the reduced conjugates RFH₂ of riboflavin (RF), and FADH₂ of the cofactor flavin adenine dinucleotide (FAD), to the corresponding flavins. Like the artemisinins, MB oxidizes FADH₂, but unlike artemisinins, it also oxidizes NAD(P)H. Like MB, artemisinins are implicated in the perturbation of redox balance in the malaria parasite by interfering with parasite flavoenzyme disulfide reductases. The oxidation of LMB by artemisinin is inhibited by chloroquine (CQ), an inhibition that is abruptly reversed by verapamil (VP). CQ also inhibits artemisinin-mediated oxidation of RFH₂ generated from N-benzyl-1,4-dihydronicotinamide (BNAH)-RF, or FADH₂ generated from NADPH or NADPH-Fre, an effect that is also modulated by verapamil. The inhibition likely proceeds by the association of LMB or dihydroflavin with CQ, possibly involving donor-acceptor or π complexes that hinder oxidation by artemisinin. VP competitively associates with CQ, liberating LMB or dihydroflavin from their respective CQ complexes. The observations explain the antagonism between CQ-MB and CQ-artemisinins in vitro, and are reconcilable with CQ perturbing intraparasitic redox homeostasis. They further suggest that a VP-CQ complex is a means by which VP reverses CQ resistance, wherein such a complex is not accessible to the putative CQ-resistance transporter (PfCRT).
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Affiliation(s)
- Richard K Haynes
- Department of Chemistry, Institute of Molecular Technology for Drug Discovery and Synthesis, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P.R. China.
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Haynes RK, Cheu KW, Tang MMK, Chen MJ, Guo ZF, Guo ZH, Coghi P, Monti D. Reactions of Antimalarial Peroxides with Each of Leucomethylene Blue and Dihydroflavins: Flavin Reductase and the Cofactor Model Exemplified. ChemMedChem 2010; 6:279-91. [DOI: 10.1002/cmdc.201000508] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2010] [Indexed: 11/07/2022]
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Haynes RK, Chan WC, Wong HN, Li KY, Wu WK, Fan KM, Sung HHY, Williams ID, Prosperi D, Melato S, Coghi P, Monti D. Facile oxidation of leucomethylene blue and dihydroflavins by artemisinins: relationship with flavoenzyme function and antimalarial mechanism of action. ChemMedChem 2010; 5:1282-99. [PMID: 20629071 DOI: 10.1002/cmdc.201000225] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The antimalarial drug methylene blue (MB) affects the redox behaviour of parasite flavin-dependent disulfide reductases such as glutathione reductase (GR) that control oxidative stress in the malaria parasite. The reduced flavin adenine dinucleotide cofactor FADH(2) initiates reduction to leucomethylene blue (LMB), which is oxidised by oxygen to generate reactive oxygen species (ROS) and MB. MB then acts as a subversive substrate for NADPH normally required to regenerate FADH(2) for enzyme function. The synergism between MB and the peroxidic antimalarial artemisinin derivative artesunate suggests that artemisinins have a complementary mode of action. We find that artemisinins are transformed by LMB generated from MB and ascorbic acid (AA) or N-benzyldihydronicotinamide (BNAH) in situ in aqueous buffer at physiological pH into single electron transfer (SET) rearrangement products or two-electron reduction products, the latter of which dominates with BNAH. Neither AA nor BNAH alone affects the artemisinins. The AA-MB SET reactions are enhanced under aerobic conditions, and the major products obtained here are structurally closely related to one such product already reported to form in an intracellular medium. A ketyl arising via SET with the artemisinin is invoked to explain their formation. Dihydroflavins generated from riboflavin (RF) and FAD by pretreatment with sodium dithionite are rapidly oxidised by artemisinin to the parent flavins. When catalytic amounts of RF, FAD, and other flavins are reduced in situ by excess BNAH or NAD(P)H in the presence of the artemisinins in the aqueous buffer, they are rapidly oxidised to the parent flavins with concomitant formation of two-electron reduction products from the artemisinins; regeneration of the reduced flavin by excess reductant maintains a catalytic cycle until the artemisinin is consumed. In preliminary experiments, we show that NADPH consumption in yeast GR with redox behaviour similar to that of parasite GR is enhanced by artemisinins, especially under aerobic conditions. Recombinant human GR is not affected. Artemisinins thus may act as antimalarial drugs by perturbing the redox balance within the malaria parasite, both by oxidising FADH(2) in parasite GR or other parasite flavoenzymes, and by initiating autoxidation of the dihydroflavin by oxygen with generation of ROS. Reduction of the artemisinin is proposed to occur via hydride transfer from LMB or the dihydroflavin to O1 of the peroxide. This hitherto unrecorded reactivity profile conforms with known structure-activity relationships of artemisinins, is consistent with their known ability to generate ROS in vivo, and explains the synergism between artemisinins and redox-active antimalarial drugs such as MB and doxorubicin. As the artemisinins appear to be relatively inert towards human GR, a putative model that accounts for the selective potency of artemisinins towards the malaria parasite also becomes apparent. Decisively, ferrous iron or carbon-centered free radicals cannot be involved, and the reactivity described herein reconciles disparate observations that are incompatible with the ferrous iron-carbon radical hypothesis for antimalarial mechanism of action. Finally, the urgent enquiry into the emerging resistance of the malaria parasite to artemisinins may now in one part address the possibilities either of structural changes taking place in parasite flavoenzymes that render the flavin cofactor less accessible to artemisinins or of an enhancement in the ability to use intra-erythrocytic human disulfide reductases required for maintenance of parasite redox balance.
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Affiliation(s)
- Richard K Haynes
- Department of Chemistry, Institute of Molecular Technology for Drug Discovery and Synthesis, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P.R. China.
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Waknine-Grinberg JH, Hunt N, Bentura-Marciano A, McQuillan JA, Chan HW, Chan WC, Barenholz Y, Haynes RK, Golenser J. Artemisone effective against murine cerebral malaria. Malar J 2010; 9:227. [PMID: 20691118 PMCID: PMC2928250 DOI: 10.1186/1475-2875-9-227] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2010] [Accepted: 08/09/2010] [Indexed: 11/12/2022] Open
Abstract
Background Artemisinins are the newest class of drug approved for malaria treatment. Due to their unique mechanism of action, rapid effect on Plasmodium, and high efficacy in vivo, artemisinins have become essential components of malaria treatment. Administration of artemisinin derivatives in combination with other anti-plasmodials has become the first-line treatment for uncomplicated falciparum malaria. However, their efficiency in cases of cerebral malaria (CM) remains to be determined. Methods The efficacy of several artemisinin derivatives for treatment of experimental CM was evaluated in ICR or C57BL/6 mice infected by Plasmodium berghei ANKA. Both mouse strains serve as murine models for CM. Results Artemisone was the most efficient drug tested, and could prevent death even when administered at relatively late stages of cerebral pathogenesis. No parasite resistance to artemisone was detected in recrudescence. Co-administration of artemisone together with chloroquine was more effective than monotherapy with either drug, and led to complete cure. Artemiside was even more effective than artemisone, but this substance has yet to be submitted to preclinical toxicological evaluation. Conclusions Altogether, the results support the use of artemisone for combined therapy of CM.
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Affiliation(s)
- Judith H Waknine-Grinberg
- Department of Microbiology and Molecular Genetics, The Hebrew University of Jerusalem, Jerusalem, 91120, Israel
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Coghi P, Basilico N, Taramelli D, Chan WC, Haynes R, Monti D. Interaction of Artemisinins with Oxyhemoglobin Hb-FeII, Hb-FeII, CarboxyHb-FeII, Heme-FeII, and Carboxyheme FeII: Significance for Mode of Action and Implications for Therapy of Cerebral Malaria. ChemMedChem 2009; 4:2045-53. [DOI: 10.1002/cmdc.200900342] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Fuochi P, Marconi G, Mulazzani Q. Radiolytically induced one-electron reduction of artemisinin in H2O/ethanol (1:1 v/v) solution: a pulse radiolysis study. Int J Radiat Biol 2009; 81:319-26. [PMID: 16019941 DOI: 10.1080/09553000500141355] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The aim was to obtain information on the one-electron reduction of the antimalarial natural drug artemisinin (ART). The pulse radiolysis of ART in H(2)O/ethanol (EtOH) (1:1 v/v) solution was studied in the absence and presence of the so-called redox indicators N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD), Fe(CN)6(4-), 1,1'-dimethyl-4,4'-bipyridinium dichloride (methyl viologen, MV(2+)) and Fe(CN)6(3-). In an argon-purged solution, ART reacts with solvated electrons (es(-)) with k=4.4 x 10(9) dm(3) mol(-1) s(-1) generating an absorption band rising in the ultraviolet region similar to the spectrum of the CH3(*)CHOH radical. The species originating from the reaction between ART and es(-) do not show any appreciable reactivity toward Fe(CN)6(4-), TMPD, MV(2+) and Fe(CN)6(3-). The experiments performed in the presence of ART and MV(2+) have provided strong support to the idea that the first species obtained from the addition of the electron, which is believed to occur at the endoperoxide group level, undergoes a rapid (k on the order of 10(8) s(-1) or higher) intramolecular rearrangement to give species, most likely carbon-centred radicals, that show some reactivity towards the methyl viologen radical cation (MV(*+)).
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Affiliation(s)
- Pg Fuochi
- Instituto per la Sintesi Organica e la Fotoreattivitá, Consiglio Nazionale delle Ricerche, Bologna, Italy
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Griesbeck A, Blunk D, El-Idreesy T, Raabe A. Bicyclic Peroxides and Perorthoesters with 1,2,4-Trioxane Structures. Angew Chem Int Ed Engl 2007; 46:8883-6. [DOI: 10.1002/anie.200701397] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Griesbeck A, Blunk D, El-Idreesy T, Raabe A. Bicyclische Peroxide und Perorthoester mit 1,2,4-Trioxanstruktur. Angew Chem Int Ed Engl 2007. [DOI: 10.1002/ange.200701397] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Haynes RK, Chan WC, Lung CM, Uhlemann AC, Eckstein U, Taramelli D, Parapini S, Monti D, Krishna S. The Fe2+-Mediated Decomposition, PfATP6 Binding, and Antimalarial Activities of Artemisone and Other Artemisinins: The Unlikelihood of C-Centered Radicals as Bioactive Intermediates. ChemMedChem 2007; 2:1480-97. [PMID: 17768732 DOI: 10.1002/cmdc.200700108] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The results of Fe(2+)-induced decomposition of the clinically used artemisinins, artemisone, other aminoartemisinins, 10-deoxoartemisinin, and the 4-fluorophenyl derivative have been compared with their antimalarial activities and their ability to inhibit the parasite SERCA PfATP6. The clinical artemisinins and artemisone decompose under aqueous conditions to give mixtures of C radical marker products, carbonyl compounds, and reduction products. The 4-fluorophenyl derivative and aminoartemisinins tend to be inert to aqueous iron(II) sulfate and anhydrous iron(II) acetate. Anhydrous iron(II) bromide enhances formation of the carbonyl compounds and provides a deoxyglycal from DHA and enamines from the aminoartemisinins. Ascorbic acid (AA) accelerates the aqueous Fe(2+)-mediated decompositions, but does not alter product distribution. 4-Oxo-TEMPO intercepts C radicals from a mixture of an antimalaria-active trioxolane, 10-deoxoartemisinin, and anhydrous iron(II) acetate to give trapped products in 73 % yield from the trioxolane, and 3 % from the artemisinin. Artemisone provides a trapped product in 10 % yield. Thus, in line with its structural rigidity, only the trioxolane provides a C radical eminently suited for intermolecular trapping. In contrast, the structural flexibility of the C radicals from the artemisinins allows facile extrusion of Fe(2+) and collapse to benign isomerization products. The propensity towards the formation of radical marker products and intermolecular radical trapping have no relationship with the in vitro antimalarial activities of the artemisinins and trioxolane. Desferrioxamine (DFO) attenuates inhibition of PfATP6 by, and antagonizes antimalarial activity of, the aqueous Fe(2+)-susceptible artemisinins, but has no overt effect on the aqueous Fe(2+)-inert artemisinins. It is concluded that the C radicals cannot be responsible for antimalarial activity and that the Fe(2+)-susceptible artemisinins may be competitively decomposed in aqueous extra- and intracellular compartments by labile Fe(2+), resulting in some attenuation of their antimalarial activities. Interpretations of the roles of DFO and AA in modulating antimalarial activities of the artemisinins, and a comparison with antimalarial properties of simple hydroperoxides and their behavior towards thapsigargin-sensitive SERCA ATPases are presented. The general basis for the exceptional antimalarial activities of artemisinins in relation to the intrinsic activity of the peroxide within the uniquely stressed environment of the malaria parasite is thereby adumbrated.
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Affiliation(s)
- Richard K Haynes
- Department of Chemistry, Open Laboratory of Chemical Biology, Institute of Molecular Technology for Drug Discovery and Synthesis, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, PR China.
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Haynes RK, Chan HW, Lung CM, Ng NC, Wong HN, Shek LY, Williams ID, Cartwright A, Gomes MF. Artesunate and Dihydroartemisinin (DHA): Unusual Decomposition Products Formed under Mild Conditions and Comments on the Fitness of DHA as an Antimalarial Drug. ChemMedChem 2007; 2:1448-63. [PMID: 17694524 DOI: 10.1002/cmdc.200700064] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Artesunate drug substance, for which a rectal capsule formulation is under development for the treatment of severe malaria, when heated at 100 degrees C for 39 h gives beta-artesunate, artesunate dimers, 9,10-anhydrodihydroartemisinin (glycal), a DHA beta-formate ester, and smaller amounts of other products that arise via intermediate formation of dihydroartemisinin (DHA) and subsequent thermal degradation. Solid DHA at 100 degrees C provides an epimeric mixture of a known peroxyhemiacetal, arising via ring opening to a hydroperoxide and re-closure, smaller amounts of a 3:1 mixture of epimers of a known tricarbonyl compound, and a single epimer of a new dicarbonyl compound. The latter arises via homolysis of the peroxide and an ensuing cascade of alpha-cleavage reactions which leads to loss of formic acid incorporating the C10 carbonyl group of DHA exposed by this 'unzipping' cascade. The tricarbonyl compound that arises via peroxide homolysis and extrusion of formic acid from a penultimate hydroxyformate ester incorporating C12 of the original DHA, is epimeric at the exocyclic 1''-aldehyde, and not in the cyclohexanone moiety. It is converted into the dicarbonyl compound by peroxide-induced deformylation. The dicarbonyl compound is not formed during anhydrous ferrous bromide mediated decomposition of DHA at room temperature, which provides the 1''-R epimer of the tricarbonyl compound as the dominant product; this equilibrates at room temperature to the 3:1 mixture of epimers of the tricarbonyl compound obtained from thermolysis. Each of artesunate and DHA decomposes readily under aqueous acidic conditions to provide significant amounts of the peroxyhemiacetal, which, like DHA, decomposes to the inert end product 2-deoxyartemisinin under acidic or basic conditions. DHA and the peroxyhemiacetal are the principal degradants in aged rectal capsule formulations of artesunate. TGA analysis and thermal degradation of DHA reveals a thermal lability which would pose a problem not only in relation to ICH stability testing guidelines, but in the use of DHA in fixed formulations currently under development. This thermolability coupled with the poor physicochemical properties and relative oral bioavailability of DHA suggests that it is inferior to artesunate in application as an antimalarial drug.
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Affiliation(s)
- Richard K Haynes
- Department of Chemistry, Open Laboratory of Chemical Biology, Institute of Molecular Technology for Drug Discovery and Synthesis, Institute of The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, PR China.
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Stocks P, Bray P, Barton V, Al-Helal M, Jones M, Araujo N, Gibbons P, Ward S, Hughes R, Biagini G, Davies J, Amewu R, Mercer A, Ellis G, O'Neill P. Evidence for a Common Non-Heme Chelatable-Iron-Dependent Activation Mechanism for Semisynthetic and Synthetic Endoperoxide Antimalarial Drugs. Angew Chem Int Ed Engl 2007. [DOI: 10.1002/ange.200604697] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Stocks PA, Bray PG, Barton VE, Al-Helal M, Jones M, Araujo NC, Gibbons P, Ward SA, Hughes RH, Biagini GA, Davies J, Amewu R, Mercer AE, Ellis G, O'Neill PM. Evidence for a Common Non-Heme Chelatable-Iron-Dependent Activation Mechanism for Semisynthetic and Synthetic Endoperoxide Antimalarial Drugs. Angew Chem Int Ed Engl 2007; 46:6278-83. [PMID: 17640025 DOI: 10.1002/anie.200604697] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Paul A Stocks
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
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Schlitzer M. Malaria Chemotherapeutics Part I: History of Antimalarial Drug Development, Currently Used Therapeutics, and Drugs in Clinical Development. ChemMedChem 2007; 2:944-86. [PMID: 17530725 DOI: 10.1002/cmdc.200600240] [Citation(s) in RCA: 179] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Since ancient times, humankind has had to struggle against the persistent onslaught of pathogenic microorganisms. Nowadays, malaria is still the most important infectious disease worldwide. Considerable success in gaining control over malaria was achieved in the 1950s and 60s through landscaping measures, vector control with the insecticide DDT, and the widespread administration of chloroquine, the most important antimalarial agent ever. In the late 1960s, the final victory over malaria was believed to be within reach. However, the parasites could not be eradicated because they developed resistance against the most widely used and affordable drugs of that time. Today, cases of malaria infections are on the rise and have reached record numbers. This review gives a short description of the malaria disease, briefly addresses the history of antimalarial drug development, and focuses on drugs currently available for malaria therapy. The present knowledge regarding their mode of action and the mechanisms of resistance are explained, as are the attempts made by numerous research groups to overcome the resistance problem within classes of existing drugs and in some novel classes. Finally, this review covers all classes of antimalarials for which at least one drug candidate is in clinical development. Antimalarial agents that are solely in early development stages will be addressed in a separate review.
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Affiliation(s)
- Martin Schlitzer
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, Marbacher Weg 6, 35032 Marburg, Germany.
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Haynes RK, Fugmann B, Stetter J, Rieckmann K, Heilmann HD, Chan HW, Cheung MK, Lam WL, Wong HN, Croft SL, Vivas L, Rattray L, Stewart L, Peters W, Robinson BL, Edstein MD, Kotecka B, Kyle DE, Beckermann B, Gerisch M, Radtke M, Schmuck G, Steinke W, Wollborn U, Schmeer K, Römer A. Artemisone--a highly active antimalarial drug of the artemisinin class. Angew Chem Int Ed Engl 2007; 45:2082-8. [PMID: 16444785 DOI: 10.1002/anie.200503071] [Citation(s) in RCA: 180] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Richard K Haynes
- Department of Chemistry, Open Laboratory of Chemical Biology, Institute of Molecular Technology for Drug Discovery and Synthesis, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, PR China.
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Haynes RK, Fugmann B, Stetter J, Rieckmann K, Heilmann HD, Chan HW, Cheung MK, Lam WL, Wong HN, Croft SL, Vivas L, Rattray L, Stewart L, Peters W, Robinson BL, Edstein MD, Kotecka B, Kyle DE, Beckermann B, Gerisch M, Radtke M, Schmuck G, Steinke W, Wollborn U, Schmeer K, Römer A. Artemisone—A Highly Active Antimalarial Drug of the Artemisinin Class. Angew Chem Int Ed Engl 2006. [DOI: 10.1002/ange.200503071] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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O'Neill PM, Rawe SL, Borstnik K, Miller A, Ward SA, Bray PG, Davies J, Oh CH, Posner GH. Enantiomeric 1,2,4-trioxanes display equivalent in vitro antimalarial activity versus Plasmodium falciparum malaria parasites: implications for the molecular mechanism of action of the artemisinins. Chembiochem 2006; 6:2048-54. [PMID: 16222725 DOI: 10.1002/cbic.200500048] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The aim of this study was to synthesise pure enantiomers of potent antimalarial 1,2,4-trioxanes, which are related to the natural antimalarial artemisinin, and then to assay each against a panel of Plasmodium falciparum strains. The working hypothesis was that if the artemisinin derivatives interact with a specific protein-target site, then there should be stereoselective differences in their activity. In five different P. falciparum isolates, however, the trioxane enantiomers (+)-7 a, (-)-7 a and (+)-7 b, (-)-7 b, showed the same level of in vitro antiparasitic activity.
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Affiliation(s)
- Paul M O'Neill
- Department of Chemistry, University of Liverpool, The Robert Robinson Laboratories, Oxford Street, Liverpool, L69 7ZD, UK.
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Schmidt TJ. Structure-Activity Relationships of Sesquiterpene Lactones. STUDIES IN NATURAL PRODUCTS CHEMISTRY 2006. [DOI: 10.1016/s1572-5995(06)80030-x] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Grellepois F, Grellier P, Bonnet-Delpon D, Bégué JP. Design, synthesis and antimalarial activity of trifluoromethylartemisinin-mefloquine dual molecules. Chembiochem 2005; 6:648-52. [PMID: 15723441 DOI: 10.1002/cbic.200400347] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Haynes RK, Chan HW, Ho WY, Ko CKF, Gerena L, Kyle DE, Peters W, Robinson BL. Convenient Access Both to Highly Antimalaria-Active 10-Arylaminoartemisinins, and to 10-Alkyl Ethers Including Artemether, Arteether, and Artelinate. Chembiochem 2005; 6:659-67. [PMID: 15812783 DOI: 10.1002/cbic.200400366] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
An economical phase-transfer method is used to prepare 10-arylaminoartemisinins from DHA and arylamines, and artemether, arteether, and artelinate from the corresponding alcohols. In vivo sc screens against Plasmodium berghei and P. yoelii in mice reveal that the p-fluorophenylamino derivative 5 g is some 13 and 70 times, respectively, more active than artesunate; this reflects the very high sc activity of 10-alkylaminoartemisinins. However, through the po route, the compounds are less active than the alkylaminoartemisinins, but still approximately equipotent with artesunate.
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Affiliation(s)
- Richard K Haynes
- Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, PR China.
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Laurent SAL, Robert A, Meunier B. C10-Modified Artemisinin Derivatives: Efficient Heme-Alkylating Agents. Angew Chem Int Ed Engl 2005; 44:2060-3; author reply 2064-5. [PMID: 15782383 DOI: 10.1002/anie.200462556] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Haynes RK. Reply to Comments on ?Highly Antimalaria-Active Artemisinin Derivatives: Biological Activity Does Not Correlate with Chemical Reactivity? Angew Chem Int Ed Engl 2005. [DOI: 10.1002/anie.200462723] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Haynes RK. Reply to Comments on ?Highly Antimalaria-Active Artemisinin Derivatives: Biological Activity Does Not Correlate with Chemical Reactivity? Angew Chem Int Ed Engl 2005. [DOI: 10.1002/ange.200462723] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Laurent SAL, Robert A, Meunier B. C10-Modified Artemisinin Derivatives: Efficient Heme-Alkylating Agents. Angew Chem Int Ed Engl 2005. [DOI: 10.1002/ange.200462556] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Griesbeck AG, El-Idreesy TT, Höinck LO, Lex J, Brun R. Novel spiroanellated 1,2,4-trioxanes with high in vitro antimalarial activities. Bioorg Med Chem Lett 2005; 15:595-7. [PMID: 15664819 DOI: 10.1016/j.bmcl.2004.11.043] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2004] [Revised: 11/13/2004] [Accepted: 11/17/2004] [Indexed: 10/26/2022]
Abstract
A remarkable increase in antimalarial in vitro activity was achieved by integration of spiroadamantane motifs in 6-alkylidene 1,2,4-trioxanes 3a-h via diastereoselective photooxygenation of allylic alcohols and subsequent BF(3)-catalyzed peroxyacetalization with adamantanone to give the active compounds 3e-h.
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Affiliation(s)
- Axel G Griesbeck
- Institut für Organische Chemie, Universität zu Köln, Greinstr. 4, D-50939 Köln, Germany.
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