1. Academic Validation
  2. Synthesis, cytotoxicity, and antiplasmodial and antitrypanosomal activity of new neocryptolepine derivatives

Synthesis, cytotoxicity, and antiplasmodial and antitrypanosomal activity of new neocryptolepine derivatives

  • J Med Chem. 2002 Aug 1;45(16):3497-508. doi: 10.1021/jm011102i.
Tim H M Jonckers 1 Sabine van Miert Kanyanga Cimanga Christian Bailly Pierre Colson Marie-Claire De Pauw-Gillet Hilde van den Heuvel Magda Claeys Filip Lemière Eddy L Esmans Jef Rozenski Ludo Quirijnen Louis Maes Roger Dommisse Guy L F Lemière Arnold Vlietinck Luc Pieters
Affiliations

Affiliation

  • 1 Department of Pharmaceutical Sciences, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium.
Abstract

On the basis of the original lead neocryptolepine or 5-methyl-5H-indolo[2,3-b]quinoline, an alkaloid from Cryptolepis sanguinolenta, derivatives were prepared using a biradical cyclization methodology. Starting from easily accessible educts, this approach allowed the synthesis of hitherto unknown compounds with a varied substitution pattern. As a result of steric hindrance, preferential formation of the 3-substituted isomers over the 1-substituted isomers was observed when cyclizing N-(3-substituted-phenyl)-N'-[2-(2-trimethylsilylethynyl)phenyl]carbodiimides. All compounds were evaluated for their activity against chloroquine-sensitive as well as chloroquine-resistant Plasmodium falciparum strains, for their activity against Trypanosoma brucei and T. cruzi, and for their cytotoxicity on human MRC-5 cells. Mechanisms of action were investigated by testing heme complexation using ESI-MS, inhibition of beta-hematin formation, DNA interactions (DNA-methyl green assay and linear dichroism), and inhibition of human Topoisomerase II. Neocryptolepine derivatives with a higher antiplasmodial activity and a lower cytotoxicity than the original lead have been obtained. This selective antiplasmodial activity was associated with inhibition of beta-hematin formation. 2-Bromoneocryptolepine was the most selective compound with an IC(50) value against chloroquine-resistant P. falciparum of 4.0 microM in the absence of cytotoxicity (IC(50) > 32 microM). Although cryptolepine, a known lead for antimalarials also originally isolated from Cryptolepis sanguinolenta, was more active (IC(50) = 2.0 microM), 2-bromoneocryptolepine showed a low affinity for DNA and no inhibition of human Topoisomerase II, in contrast to cryptolepine. Although some neocryptolepine derivatives showed a higher antiplasmodial activity than 2-bromocryptolepine, these compounds also showed a higher affinity for DNA and/or a more pronounced cytotoxicity. Therefore, 2-bromoneocryptolepine is considered as the most promising lead from the present work for new antimalarial agents. In addition, 2-bromo-, 2-nitro-, and 2-methoxy-9-cyanoneocryptolepine exhibited antitrypanosomal activity in the micromolar range in the absence of obvious cytotoxicity.

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