Browsing by Author "Kimbokota, Fikira"

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    Anticonvulsant and antimicrobial constituents from diospyros mafiensis and a novel phenylpropanoyl diterpene from isolanacauliflora
    (University of Dar es Salaam, 2005) Kimbokota, Fikira
    This thesis reports on the isolation and structural determination of natural products from the plant species Heteromorpha trifoliara (Apiaceae),isilana cauliflora (Annonaceae) and Diospyros mafiensis (Ebenaceae). The epoxy-dinaphthoquinone diosquinone was isolated from D. mafiensis as a mixture of two conformationalisomers (rotamers) and also being mixed with its positional isomer, and the triterpene lupeol. While the crude D. mafiensis extracts exhibited significant cytotoxicity (BST), antibacterial, antifungal and anticonvulsant activities, diosquinone was active against several bacteria strains, the activity being greatly enhanced in a mixture of diosquinone and its positional isomer. H. trifoliate, a plant which is used as a herbaremedy for various ailments, yielded small amounts of O-methoxyscopoletin and tetracosyl hexacosanoate, which could not be assayed for bioactivities due to paucity of the material. I. cauliflora yielded small amounts of the known prenylated indoles caulidine A {3-(1,1-dimethyl-allyl)-5-(3-methyl-but-2-enyl)- 1lH-indole), caulindole C (3,4-trans)-3-[3'-(1"'. 1"'-dimethyl-2"'-propenyl)-5'-indolylJ]-1,4-dim ethyl-4{2- [3"-(1"",1""-dimethyl-2""-propenyl)-5"-indolyl ]-ethyl-2-eny1}-cyclohex-l –ene}, polycarpol, a mixture of sterols and a new phenylpropanoy1 diterpene isolotrione (6- hydroxy-6,10,14,18-tetramethy-3-phenyl-nonadec- 17-en-2,5,16-trinone), which were also not assayed for bioactivities.
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    Semiochemicals mediating oviposition and mating behaviours of mango infesting fruity fly, bactrocera invadens
    (University of Dar es Salaam, 2011) Kimbokota, Fikira
    This thesis reports on characterisation of semiochemicals that mediate oviposition and mating behaviour of the fruit fly Bactrocera invades from three host plants namely mango, Mangifera indica; the Indian almond, Terminalia catappa; and the marula, Sclerocarya birrea. Attractive volatile components from a non-host plant, Gynandropsis gynandra that only attracted male flies as well as those in volatile emissions collected from both male and female flies were also characterized. Volatile constituents collected from both mature unripe and mature ripe fruits of Mangifera indica, Sclerocarya birrea and Terminalia catappa were identified to constitute terpenes, esters, hydrocarbons, carbonyls, alcohols and others, with terpene, alcohols and esters respectively being the most abundant. In GC-EAD analyses of these volatiles, a number of compounds in each host were found to be electrophysiologically active. Gynandropsis gynandra attracted male fruit flies in the field, and two EAG-active peaks were identified by GC-MS to represent 4-methyl-3- penten-2-one and 4-hydroxy-4-methyl-2-pentanone. Volatiles from male flies were significantly more attractive to both male and female flies. Furthermore, in GC-MS analyses these volatiles were found to constitute various groups of compounds in which esters and spiroacetals were the main constituents, This study characterized semiochemicals from host plants, one non-host plant and volatiles from male and female flies and some constituents are candidate attractants to both male and female Bactrocera invadens. Thus, the results have laid down significant groundwork in the development of effective attractant(s) from both, host plants (kairomones) and conspecifics (pheromones).