title: Antimalarial and vasorelaxant constituents of the leaves of Allanblackia monticola (Guttiferae).
abstract: Phytochemical investigation of the leaves of Allanblackia monticola led to the isolation and characterisation of five prenylated xanthones [1,6-dihydroxy-3,7-dimethoxy-2-(3-methylbut-2-enyl)xanthone 1, alpha-mangostin 2, tovophyllin A 3, allanxanthone C 4 and 1,7-dihydroxy-3-methoxy-2-(3-methylbut-2-enyl)xanthone 5], two biflavonoid derivatives (amentoflavone 6 and podocarpusflavone A 7) and one pentacyclic triterpene (friedelan-3-one 8). The structures of these compounds were established on the basis of homo- and hetero-nuclear, one- and two-dimensional, nuclear magnetic resonance. Compounds 2-8 and a crude methanolic extract of A. monticola leaves were each tested for antimalarial activity in vitro, using the chloroquine-sensitive F32 and chloroquine-resistant FcM29 strains of Plasmodium falciparum; the median inhibitory concentrations (IC(50)) recorded varied from 0.7 to 83.5 mug/ml. The cytotoxicities of the compounds and crude extract, against cultures of human melanoma cells (A375), were then investigated, and cytotoxicity/antimalarial IC(50) ratios of 0.6-16.75 were recorded. In tests involving aortic rings from guinea pigs, a crude extract of the leaves of A. monticola was found to induce concentration-dependent vasorelaxation, causing up to 82% and 42% inhibition of noradrenaline- and KCl-induced contractions, respectively. The corresponding values for compounds 2 and 6 when tested against noradrenaline-induced contractions were approximately 18% and 35%, respectively.
authors.affiliation: Department of Chemistry, Faculty of Science, University of Douala, P.O. Box 24157, Douala, Cameroon. azebaze@yahoo.com
authors.forename: A G B
authors.initials: AG
authors.lastname: Azebaze
authors.forename: A B
authors.initials: AB
authors.lastname: Dongmo
authors.forename: M
authors.initials: M
authors.lastname: Meyer
authors.forename: B M W
authors.initials: BM
authors.lastname: Ouahouo
authors.forename: A
authors.initials: A
authors.lastname: Valentin
authors.forename: E
authors.initials: E
authors.lastname: Laure Nguemfo
authors.forename: A E
authors.initials: AE
authors.lastname: Nkengfack
authors.forename: W
authors.initials: W
authors.lastname: Vierling
mesh_terms: D000818:Animals; D000962:Antimalarials / Q000032:analysis* / Q000494:pharmacology; D001011:Aorta / Q000187:drug effects; D044946:Biflavonoids / Q000032:analysis / Q000494:pharmacology; D045744:Cell Line, Tumor; D028084:Clusiaceae / Q000737:chemistry*; D004365:Drugs, Chinese Herbal / Q000032:analysis / Q000494:pharmacology; D005419:Flavonoids / Q000032:analysis / Q000494:pharmacology; D006168:Guinea Pigs; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D010936:Plant Extracts / Q000032:analysis; D018515:Plant Leaves / Q000737:chemistry*; D010963:Plasmodium falciparum / Q000187:drug effects; D014315:Triterpenes / Q000032:analysis / Q000494:pharmacology; D014665:Vasodilator Agents / Q000032:analysis* / Q000494:pharmacology; D044004:Xanthones / Q000032:analysis / Q000494:pharmacology; D000094042:Lupanes
chemical_list: D000962:Antimalarials; D044946:Biflavonoids; D004365:Drugs, Chinese Herbal; D005419:Flavonoids; D010936:Plant Extracts; D014315:Triterpenes; D014665:Vasodilator Agents; D044004:Xanthones; C508597:allanxanthone C; C094150:podocarpusflavone A; C011164:amentoflavone; C060796:friedelin; D000094042:Lupanes; C021053:mangostin