Browsing by Author "Innocent, Ester"

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    Anti-mosquito terpenoids and other constituents of selected Tanzanian plants
    (Unversity of Dar es Salaam, 2007) Innocent, Ester
    This Telesis reports on phytochemical, repellency and larvicidal investigation of seven plants species against Anopheles gambiae mosquito. During the studies structures of seventy six essential oil constituents were identified from Uvariodendron gorgonis Verde, Clausena anisata (Wild) Benth, Steganataenia araliacea Hochst, Suregada zanzibariensis Verde and lantana viburnoides ssp. Viburnoides var.kisi (A. Rich) Verde. Most of them were- tested for mosquito repellent activity. Some essential oils and methyl ketones constituents showed good repellency activity (Chapter 2). Extracts from five plant species, namely Synadenium glaucensen Verde, Kotschya uguenensis Verde L, vibumoides, and Saraliacea were screened for larvicidal activity. Four extracts, namely dichlorometlune extract from the root balk of L viburnoides (LRRD), dichloromethane root bark extract of S. araliacea (SARD) and methanol extracts from the root (KURM) and stem barks (KUSM) of K. Uguenensis showed pronounced larvicidal and insect growth disruption properties (Chapter 3) Bioassay guided fractionation of LRRD yielded four series of inseparable mixtures of closely related furanonaphthaquinone derivatives, three triterpenoids a bis-phenyl peroxide and stigmasterol (Chapter 4). Bioassay guided fractionation of SARD yielded four bisbenzocyclooctadiene lactone lignans, two fatty acids and P-sitosterol (Chapter 5) while KURM and KUSM yielded unidentified, unstable compounds as active principles, together with a butenyl monoterpene disaccharide (kotside) (Chapter 6). Although structures of the unstable compounds could not be established because of instability, they exhibited significant bioactivity which prompted further bioassay of the extract and powdered plant materials formulations. The formulations (KURP, KUSP. KURME and KUSME) showed good results reducing mosquito larval and pupal population, with complete mortality occurring in 2-8 days Chapter 6 and 7.
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    Antimicrobial flavonoids and stilbene glycosides from Uvaria Scheffleri and terminalia sericea.
    (University of Dar es Salaam, 2002) Innocent, Ester
    This Thesis reports on phytochemical and antimicrobial investigations of the three medicinal plants, Uvaria scheffleri (Annonaceae), Terminalia sericea (Combretaceae) and Zanthoxylum deremense (Rutaceae).The ethanol extract of the root bark of T. sericea exhibited antibacterial activity, although its total extract possessed neither antibacterial nor antifungal activities. The ethanol extract of T. sericea also exhibited weak cytotoxicity in the brine shrimp test. The extract upon repeated chromatography yielded the weakly antimicrobially active stilbene derivatives resveratrol, together with its two glycosides that consisted of a rutinoside sugar residue, one of the compounds also possessing a hydroxyethane group attached to one of the phenolic oxygens of the resveratrol unit: The glycosides, as well as the highly oxygenated triterpenoid sericic acid and mixture of b*-sitosterol and stigmasterol which were also isolated from T. sericea, either exhibited a mild antibacterial and/or antifungal activity, or they were completely inactive. The structure of the only highly active compound isolated from T. sericea could not be established based on the available spectral data. Extracts from the leaves and stem bark of U. scheffleri yielded four chalcones, tour favanones, one flavone, the condensed chalcone schefflerin, 3-farnesylindole, lupeol and a mixture of b*-sitosterol and stigmasterol. Some of the isolated flavonoids exhibited antifungal and/or antibacterial activities. The isolated flavonoids had ring B lacking any substituent, the chalcones occurring with the substitution pattern that was similar to the one prevalent among the isolated flavanones. This can be explained by considering the presence in U. scheffleri of a special isomeraze enzyme with specificity to catalyse the interconversion of chalcones and flavanones during the biosynthesis of these compounds. The total extract from the root bark of Zanthoxylum deremense exhibited mild antibacterial activity against Neisseria gonorrhoea (strain WHO-B 05/09/1985) but due to time limitations, the extract could not be investigated further for its constituent natural products.