Browsing by Author "Mgani, Quintino Alfonce"

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    Chemical studies of less popular constituents of Tanzanian medicinal plants with antimalarial activity
    (University of Dar es Salaam, 1990) Mgani, Quintino Alfonce
    Two Uvaries species. U. tanzaniae Verdc. And U. lucida ssp. lucida Benth, which are active against the multidrug resistant K1 strain of Plasmodium falciparum malaria parasites in vitro were phytochemically investigated. One new spiro benzopyranyl sesquiterpene, tanzanene, and the known dihydrochalcones, chamuvaretin, uvaretin, diuvaretin and isotriuvaretin were isolated from the root bark of U. tanzaniae while two new benzopyranyl sesquiterpenes, lucidene and uvarisesquiterpene D were isolated from the root bark of U. lucida ssp. lucida as well as a partially identified guaiene alcohol, selin-11(12)-en-4a-ol and the known dihydrochalcones, uvaretin, diuvaretin and chamuvaretin. The stem bark of the latter plant gave large quantities of caryophyllene oxide and two new compounds which have been named lucivaretin and uvarichalcone, respectively. Lucivaretin, which is a flavanone, can be considered as a derivative of chamuvaretin while uvarichalcone contains a naphthaquinone group and a chalcone moiety, the two being linked through a benzopyranyl ring system. All compounds were identified by combined spectroscopic methods. Known compounds were compared with authentic samples. The structure of lucidene (which is a bis benzopyranyl derivative of humulene) was established by X-ray crystallography. The benzopyranyl sesquiterpenes can be considered as biogenetically resulting from a Diels Alder cyclization between the respective sesquiterpene moiety and the quinone methide of orthohydroxytaluene. The antimalarial activity of both studied plants has been found to reside on the Cbenzylated dihydrochalcones which were isolated. However, it might be possible that other active compounds were not isolated in the course of the study.