- Antimalarial Benzimidazole Derivatives Incorporating Phenolic Mannich Base Side Chains Inhibit Microtubule and Hemozoin Formation: Structure-Activity Relationship and in Vivo Oral Efficacy Studies
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A novel series of antimalarial benzimidazole derivatives incorporating phenolic Mannich base side chains at the C2 position, which possess dual asexual blood and sexual stage activities, is presented. Structure-activity relationship studies revealed that the 1-benzylbenzimidazole analogues possessed submicromolar asexual blood and sexual stage activities in contrast to the 1H-benzimidazole analogues, which were only active against asexual blood stage (ABS) parasites. Further, the former demonstrated microtubule inhibitory activity in ABS parasites but more significantly in stage II/III gametocytes. In addition to being bona fide inhibitors of hemozoin formation, the 1H-benzimidazole analogues also showed inhibitory effects on microtubules. In vivo efficacy studies in Plasmodium berghei-infected mice revealed that the frontrunner compound 41 exhibited high efficacy (98% reduction in parasitemia) when dosed orally at 4 × 50 mg/kg. Generally, the compounds were noncytotoxic to mammalian cells.
- Dziwornu, Godwin Akpeko,Coertzen, Dina,Leshabane, Meta,Korkor, Constance M.,Cloete, Cleavon K.,Njoroge, Mathew,Gibhard, Liezl,Lawrence, Nina,Reader, Janette,Van Der Watt, Mari?tte,Wittlin, Sergio,Birkholtz, Lyn-Marie,Chibale, Kelly
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p. 5198 - 5215
(2021/05/06)
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- Antimalarial Pyrido[1,2- a]benzimidazole Derivatives with Mannich Base Side Chains: Synthesis, Pharmacological Evaluation, and Reactive Metabolite Trapping Studies
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A novel series of pyrido[1,2-a]benzimidazoles bearing Mannich base side chains and their metabolites were synthesized and evaluated for in vitro antiplasmodium activity, microsomal metabolic stability, reactive metabolite (RM) formation, and in vivo antimalarial efficacy in a mouse model. Oral administration of one of the derivatives at 4 × 50 mg/kg reduced parasitemia by 95% in Plasmodium berghei-infected mice, with a mean survival period of 16 days post-treatment. The in vivo efficacy of these derivatives is likely a consequence of their active metabolites, two of which showed potent in vitro antiplasmodium activity against chloroquine-sensitive and multidrug-resistant Plasmodium falciparum (P. falciparum) strains. Rapid metabolism was observed for all the analogues with 40% of parent compound remaining after 30 min of incubation in liver microsomes. RM trapping studies detected glutathione adducts only in derivatives bearing 4-aminophenol moiety, with fragmentation signatures showing that this conjugation occurred on the phenyl ring of the Mannich base side chain. As with amodiaquine (AQ), interchanging the positions of the 4-hydroxyl and Mannich base side group or substituting the 4-hydroxyl with fluorine appeared to block bioactivation of the AQ-like derivatives though at the expense of antiplasmodium activity, which was significantly lowered.
- Okombo, John,Brunschwig, Christel,Singh, Kawaljit,Dziwornu, Godwin Akpeko,Barnard, Linley,Njoroge, Mathew,Wittlin, Sergio,Chibale, Kelly
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p. 372 - 384
(2019/01/26)
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- Discovery of a potent non-oxime reactivator of nerve agent inhibited human acetylcholinesterase
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Organophosphorous (OP) compounds (such as nerve agents) inhibit the enzyme acetylcholinesterase (AChE) by covalent phosphylation of a key serine residue in the active site of the enzyme resulting in severe symptoms and ultimately death. OP intoxications are currently treated by administration of certain oxime compounds. The presently fielded oximes reactivate OP-inhibited AChE by liberating the phosphylated serine. Recent research towards new reactivators was predominantly devoted to design, synthesis and evaluation of new oxime-based compounds dedicated to overcoming some of the major limitations such as their intrinsic toxicity, their permanent charge which thwarts penetration of brain tissues and their inability to effectively reactivate all types of nerve agent inhibited AChEs. However, in over six decades of research only limited success has been achieved, indicating that there is a need for alternative classes of compounds that could reactivate OP-inhibited AChE. Recently, a number of non-oxime compounds was discovered in which the 4-amino-2-((diethylamino)methyl)phenol (ADOC) motif proved to be able to reactivate OP-inhibited AChE to some extent. In this paper several structural derivatives of ADOC were synthesized and screened for their ability to reactivate human AChE (hAChE) inhibited by the nerve agents VX, sarin, tabun, cyclosarin and paraoxon. We here disclose that one of those compounds showed a remarkable ability to reactivate OP-inhibited hAChE in vitro and that it is the most potent non-oxime reported to date.
- de Koning, Martijn Constantijn,Horn, Gabriele,Worek, Franz,van Grol, Marco
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p. 151 - 160
(2018/08/10)
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- Pyrido[3,2-b]indol-4-yl-amines - Synthesis and investigation of activity against malaria
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Starting with 3-aminoindole-2-carboxylic acid ester 1 the annulated pyrido[3,2-b]indoles 6 and 8 were synthesized as key substances. The 4-chloropyridine derivative 8 reacted with the phenol Mannich bases 11 and the novaldiamine base 13, respectively, to yield the amodiaquine and cycloquine analogues 12 as well as the chloroquine analogue 14. The stability of the compounds 12 and 14 were proven by the half wave potentials measured by differential pulse voltammetry. Compounds 12 and 14 were tested for in vitro antimalarial activity using a chloroquine sensitive and a chloroquine resistant Plasmodium falciparum strain. The highest activity was shown by 12g with IC 50 values of 50 nM and 38 nM, respectively. The in vivo activity of 12g was tested in Plasmodium vinckei infected mice resulting in ED50 values of 22 mg/kg and 26 mg/kg after intraperitoneal and oral administration, respectively.
- Goerlitzer,Kramer,Meyer,Walter,Jomaa,Wiesner
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p. 243 - 250
(2007/10/03)
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- Anti-malaria active 10-H-indolo[3,2-b]quinoline-11-yl-amines. Part 1: Phenol-Mannich-bases of the amodiaquine and cycloquine type
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The 11-chloro-quindoline derivatives 3 react with 4-aminophenol and the mono- and bis-phenol-Mannich-bases 6 to yield the 10 H-indolo[3,2-b]quinoline-11-ylamines 4 and 7. The amodiaquine analogue 7a as the best of all compounds shows a comparable activity with choroquine and inhibits a multiresistant Plasmodium falciparum strain at the same concentration. Compound 7e from the cycloquine-type was selected for an in vivo antitumor screening programme.
- Gorlitzer,Stockmann,Walter
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p. 231 - 235
(2007/10/02)
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