Chemistry Department

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Browsing Chemistry Department by Author "Avery, Vicky M."

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    Bioactivities of extracts, debromolaurenterol and fucosterol from macroalgae species
    (Dar es Salaam University Press, 2018-06) Begum, Sartaz; Nyandoro, Stephen S.; Buriyo, Amelia S.; Makangara, John J; Munissi, Joan J.E; Duffy, Sandra; Avery, Vicky M.; Erdelyi, Mate
    Parasitic diseases including malaria, and other numerous microbial infections and physiological diseases are threatening the global population. Tanzanian coast shores are endowed with a variety of macroalgae (seaweeds), hitherto unsystematically explored to establish their biomedical potentials. Thus, antiplasmodial activity using malarial imaging assay, antimicrobial activity using microplate dilution technique, antioxidant activity using DPPH radical scavenging method and cytotoxicity using brine shrimp test were carried out on crude extracts from the selected species of algae (Acanthophora spicifera, Cystoseira myrica, Cystoseira trinodis, Laurencia filiformis, Padina boryana, Sargassum oligocystum, Turbinaria crateriformis, Ulva fasciata and Ulva reticulata) occurring along the coast of Tanzania. The extracts showed antimicrobial activities with MIC ranging from 0.3- 5.0 μg/mL against Staphylococcus aureus, Streptococcus pyogenes, Pseudomonas aeruginosa, Escherichia coli, Candida albicans and Cryptococcus neoformans; DPPH radical scavenging activity at EC50 1.0- 100 μg/mL and cytotoxicity on brine shrimp larvae with LC50 value ranging from20 - 1000 μg/mL. The extracts from C. myrica and P. boryana inhibited growth of Plasmodium falciparum (3D7 strain) by 80 and 71%, respectively at 40 μg/mL while a sesquiterpene debromolaurinterol (1) which was chromatographically isolated from C. myrica exhibited antiplasmodial activity with IC50 20 μM whereas a sterol fucosterol (2) from P. boryana showed weak activity at 40 μM. Bioactivities portrayed by the investigated extracts indicate their ingredients as potential sources of bioactive agents that warrant further explorations.
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    Polyoxygenated Cyclohexenes and Other Constituents of Cleistochlamys kirkii Leaves
    (American Chemical Society, 2016-12-21) Nyandoro, Stephen S.; Munissi, Joan J.E; Gruhonjic, Amra; Duffy, Sandra; Pan, FangFang; Puttreddy, Rakesh; Holleran, John P.; Fitzpatrick, Paul A.; Pelletier, Jerry; Avery, Vicky M.; Rissanen, Kari; Erdelyi, Mate
    Thirteen new metabolites, including the polyoxygenated cyclohexene derivatives cleistodiendiol (1), cleistodienol B (3), cleistenechlorohydrins A (4) and B (5), cleistenediols A–F (6–11), cleistenonal (12), and the butenolide cleistanolate (13), 2,5-dihydroxybenzyl benzoate (cleistophenolide, 14), and eight known compounds (2, 15–21) were isolated from a MeOH extract of the leaves of Cleistochlamys kirkii. The purified metabolites were identified by NMR spectroscopic and mass spectrometric analyses, whereas the absolute configurations of compounds 1, 17, and 19 were established by single-crystal X-ray diffraction. The configuration of the exocyclic double bond of compound 2 was revised based on comparison of its NMR spectroscopic features and optical rotation to those of 1, for which the configuration was determined by X-ray diffraction. Observation of the co-occurrence of cyclohexenoids and heptenolides in C. kirkii is of biogenetic and chemotaxonomic significance. Some of the isolated compounds showed activity against Plasmodium falciparum (3D7, Dd2), with IC50 values of 0.2–40 μM, and against HEK293 mammalian cells (IC50 2.7–3.6 μM). While the crude extract was inactive at 100 μg/mL against the MDA-MB-231 triple-negative breast cancer cell line, some of its isolated constituents demonstrated cytotoxic activity with IC50 values ranging from 0.03–8.2 μM. Compound 1 showed the most potent antiplasmodial (IC50 0.2 μM) and cytotoxic (IC50 0.03 μM, MDA-MB-231 cell line) activities. None of the compounds investigated exhibited translational inhibitory activity in vitro at 20 μM.