College of Natural and Applied Sciences

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Browsing College of Natural and Applied Sciences by Subject "a cyclitol and other constituents"

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    Bioactive flavonoids, imidodrima noids , a cyclitol and other constituents of some annonacin species from coastal Tanzania
    (University of Dar es Salaam, 2004) Gumula, Ivan
    Investigations reported in this Thesis were aimed at the isolation of biologically active and other constituents from Uvaria acuminata and Artabotrys brachypetalus as part of ongoing phytochemical investigations at the Department of Chemistry, University of Dar es Salaam on plant species of the family Annonaceae. Plant species from the genera Uvaria and Artabotrys are widely used in herbal remedies. The stem bark of Uvaria acuminata yielded uvaretin, isouvaretin, diuvaretin, isochamuvaritin, uvangoletin and benzoic acid. Attempts to derivatise uvaretin yielded 4',2"-0-diacetyluvaretin, 2"-0-acetyluvaretin and acetyl 6-(2-acetoxy- benzyl)-3-benzyl-5-hydroxy-2-methyl-4-oxo-4//-chromene-7-ylate. Uvaretin displayed cytotoxicity in the brine shrimp lethality test with an LC50 value of 43.58 (ig/ml, strong antibacterial activity against Bacillus anthracis, Staphylococcus aureus and Salmonella typhimurium and moderate activity against Shigella boydii and Klebsiella pneumoniae. It also displayed weak antifungal activity against Candida albicans. The cytotoxicity and antimicrobial activities of both 4',2"-0- diacetyluvaretin and 2"-0-acetyluvaretin were weaker than those of uvaretin, thus, indicating the influence of phenolic OH groups to the antimicrobial activity of C- benzyl dihydrochalcones. Isochamuvaritin exhibited weak activity against Proteus species and S. typhimurium. The stem bark of Artabotrys brachypetalus collected from Kwamngumi forest in Tanga region (Tanzania) in 1999 yielded two imidodrimanoids whose molecular structures are still tentative due to inadequate spectral data. The stem bark of A. brachypetalus collected in the year 2002 (also from Kwamngumi forest) yielded 4-methylene-tetrahydrofuran-3-ol and a dicyclitol with interesting NMR spectral characteristics and whose structure is tentative, having been established based on recorded and simulated spectral data. 4-Methylene- tetrahydrofuran-3-ol was inactive in all antifungal and antibacterial bioassays.