Planta Med 2014; 80 - SL32
DOI: 10.1055/s-0034-1394520

Antitrypanocidal activity of quinoline alkaloids from the roots of Waltheria indica

S Cretton 1, L Bréant 1, L Pourrez 1, L Marcourt 1, C Ambuehl 1, R Perozzo 1, M Kaiser 2, 3, M Cuendet 1, P Christen 1
  • 1School of Pharmaceutical Sciences, University of Geneva, University of Lausanne, Quai Ernest-Ansermet 30, CH-1211 Geneva 4, Switzerland
  • 2Swiss Tropical and Public Health Institute, Socinstr. 57, Basel, Switzerland
  • 3University of Basel, Petersplatz 1, 4003 Basel, Switzerland

Waltheria indica L. (Malvaceae) is a short-lived shrub that can reach up to 2 m in height and is widespread in subtropical and tropical regions. In traditional medicine, the plant is used as decoction, infusion, maceration, is chewed or directly applied on wounds. Many ailments are treated with this herb, such as skin ulcer, rheumatism, diarrhea, hemorrhoids, asthma and teeth infection [1]. In Burkina Faso, the roots and aerial parts are used against malaria [2], whereas in Niger/Nigeria herdsmen give the whole plant to cattle as a tonic, suggesting a possible activity against animal sleeping sickness [3]. As part of our ongoing investigation of natural products with antiparasitic activity, extracts were prepared from the roots of Waltheria indica and screened against protozoa from the genera Trypanosoma, Leishmania and Plasmodium. Subsequent fractionation led to the isolation and characterization of twelve quinoline alkaloids, i.e. 8-deoxoantidesmone (1), waltheriones A and C (2, 3), waltheriones E-K (4 – 10), 1-demethoxy-4-methoxy-waltherione G-N-oxide (11) and antidesmone (12). Their chemical structures were established by NMR investigations including 1H-, 13C-NMR, HSQC, HMBC, COSY and NOESY experiments, UV, IR, and mass spectrometry. To our knowledge, compounds 4 – 11 have not yet been described in the literature. Compounds 6, 7 and 10 showed potent and selective growth inhibition towards Trypanosoma cruzi with IC50 values between 0.02 and 0.04µM, which is significantly lower than the reference drug benznidazole (2.22µM). The cytotoxicity of alkaloids 1, 4, 6, 7, 9 and 10 towards mouse skeletal L-6 cells was relatively high with IC50 values lower than 1µM. However, compound 3 showed a lower cytotoxicity (IC50: 101µM) compared to its trypanocidal activity (IC50: 1.93µM), resulting in a selectivity index (IC50 L-6/IC50 T. cruzi) superior to 50. Hence this alkaloid conforms to hit activity criteria with respect to T. cruzi as required by the WHO/TDR [4].

Keywords: Waltheria indica, quinoline alkaloid, waltherione, trypanocidal activity, Trypanosoma cruzi


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