title: Antiplasmodial and cytotoxic activities of the constituents of Turraea robusta and Turraea nilotica.
abstract: BACKGROUND
  Turraea robusta and Turraea nilotica are African medicinal plants used for the treatment of a wide variety of diseases, including malaria. The genus Turraea is rich in limonoids and other triterpenoids known to possess various biological activities.
  
  
  METHODS
  From the stem bark of T. robusta six compounds, and from various parts of T. nilotica eleven compounds were isolated by the use of a combination of chromatographic techniques. The structures of the isolated compounds were elucidated using NMR and MS, whilst the relative configuration of one of the isolated compounds, toonapubesin F, was established by X-ray crystallography. The antiplasmodial activities of the crude extracts and the isolated constituents against the D6 and W2 strains of Plasmodium falciparum were determined using the semiautomated micro dilution technique that measures the ability of the extracts to inhibit the incorporation of (G-(3)H, where G is guanine) hypoxanthine into the malaria parasite. The cytotoxicity of the crude extracts and their isolated constituents was evaluated against the mammalian cell lines African monkey kidney (vero), mouse breast cancer (4T1) and human larynx carcinoma (HEp2).
  
  
  RESULTS
  The extracts showed good to moderate antiplasmodial activities, where the extract of the stem bark of T. robusta was also cytotoxic against the 4T1 and the HEp2 cells (IC50<10 μg/ml). The compounds isolated from these extracts were characterized as limonoids, protolimonoids and phytosterol glucosides. These compounds showed good to moderate activities with the most active one being azadironolide, IC50 2.4 ± 0.03 μM and 1.1 ± 0.01 μM against the D6 and W2 strains of Plasmodium falciparum, respectively; all other compounds possessed IC50 14.4-40.5 μM. None of the compounds showed significant cytotoxicity against vero cells, yet four of them were toxic against the 4T1 and HEp2 cancer cell lines with piscidinol A having IC50 8.0 ± 0.03 and 8.4 ± 0.01 μM against the 4T1 and HEp2 cells, respectively. Diacetylation of piscidinol A resulted in reduced cytotoxicity.
  
  
  CONCLUSIONS
  From the medicinal plants T. robusta and T. nilotica, twelve compounds were isolated and characterized; two of the isolated compounds, namely 11-epi-toonacilin and azadironolide showed good antiplasmodial activity with the highest selectivity indices.
authors: Centre for Traditional Medicine and Drug Research, Kenya Medical Research Institute, P.O. Box 54840-00200, Nairobi, Kenya; Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg SE-41296, Sweden.
authors: Beatrice N
authors: BN
authors: Irungu
authors: Centre for Traditional Medicine and Drug Research, Kenya Medical Research Institute, P.O. Box 54840-00200, Nairobi, Kenya.
authors: Nicholas
authors: N
authors: Adipo
authors: Centre for Traditional Medicine and Drug Research, Kenya Medical Research Institute, P.O. Box 54840-00200, Nairobi, Kenya.
authors: Jennifer A
authors: JA
authors: Orwa
authors: Centre for Biotechnology Research and Development, Kenya Medical Research Institute, P.O. Box 54840-00200, Nairobi, Kenya.
authors: Francis
authors: F
authors: Kimani
authors: Institut für Chemie, Universität Potsdam, Karl-Liebknecht-Str. 24-25, D-14476 Potsdam, Germany.
authors: Matthias
authors: M
authors: Heydenreich
authors: Department of Chemistry, University of Nairobi, P.O. Box 30197-00100, Nairobi, Kenya.
authors: Jacob O
authors: JO
authors: Midiwo
authors: Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg SE-41296, Sweden.
authors: Per
authors: P
authors: Martin Björemark
authors: Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg SE-41296, Sweden.
authors: Mikael
authors: M
authors: Håkansson
authors: Department of Chemistry, University of Nairobi, P.O. Box 30197-00100, Nairobi, Kenya. Electronic address: ayenesew@uonbi.ac.ke.
authors: Abiy
authors: A
authors: Yenesew
authors: Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg SE-41296, Sweden; Swedish NMR Centre, University of Gothenburg, Gothenburg SE-40530 Sweden. Electronic address: mate@chem.gu.se.
authors: Máté
authors: M
authors: Erdélyi
mesh_terms: D000818:Animals; D000962:Antimalarials / Q000494:pharmacology*; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D004354:Drug Screening Assays, Antitumor; D006801:Humans; D036701:Limonins / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D029582:Meliaceae / Q000737:chemistry*; D051379:Mice; D008958:Models, Molecular; D024301:Plant Bark / Q000737:chemistry; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology; D018547:Plant Stems / Q000737:chemistry; D010963:Plasmodium falciparum / Q000187:drug effects; D014709:Vero Cells
chemical_list: D000962:Antimalarials; D000972:Antineoplastic Agents, Phytogenic; D036701:Limonins; D010936:Plant Extracts
keywords: Antiplasmodial activity; Azadironolide; Cytotoxicity; Limonoid; Toonacilin; Toonapubesins F; Turraea nilotica; Turraea robusta