Antiprotozoal activity of Xanthium brasilicum and bioactivity-guided isolation of its active constituents

A. M. M. Nour; S. A. Khalid; W. E. Abdallah; M. Kaiser; R. Brun; T. J. Schmidt

doi:10.1055/s-2006-949872

Planta Medica, Table of Contents

Antiprotozoal activity of Xanthium brasilicum and bioactivity-guided isolation of its active constituents

AMM Nour ¹, SA Khalid ², WE Abdallah ³, M Kaiser ⁴, R Brun ⁴, TJ Schmidt ¹

¹Westfälische Wilhelms-Universität, Institut für Pharmazeutische Biologie und Phytochemie, Hittorfstraße 56, D-48149 Münster, Germany
²University of Khartoum, Department of Pharmacognosy, Faculty of Pharmacy, P.O. box 1996, Khartoum, Sudan
³Medicinal and Aromatic Plants Research Institute, P.O. box 2404-Khartoum, Sudan
⁴Swiss Tropical Institute, Socinstraße 57, CH-4002 Basel, Switzerland

Abstract

In the course of a screening of Sudanese Asteraceae against protozoa causing tropical diseases, a crude DCM extract of Xanthium brasilicum Vell. was found highly active against Trypanosoma brucei rhodesiense (East African Sleeping Sickness, IC₅₀=0.1µg/mL). Bioactivity-guided fractionation yielded two monomeric and two dimeric xanthanolide sesquiterpene lactones (STL 1-4), all highly active. The unusual compound 5 was almost inactive as a pure compound. Compound 1 (8-epixanthatin) showed the lowest IC₅₀ values against T. brucei and Leishmania donovani (visceral Leishmaniasis) of 0.34µM and 0.60µM, respectively. All compounds were reported as constituents of X. pungens [1] but no information on their bioactivity existed. Structure-activity studies with a variety of STL [2] are in progress.

Acknowledgements: A. M. M. Nour acknowledges a scholarship from the German Academic Exchange Service (DAAD).

References: 1. Ahmed, A. A. et al. (1990), Phytochemistry 29: 2211–2215. 2. Schmidt, T. J. et al. (2002), Planta Med. 68: 750–751.