Browsing by Author "Mgina, Clarence A."

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    Antifungal Enantiomeric Styrylpyrones from Sanrafaelia ruffonammari and Ophrypetalum odoratum
    (Springer Link, 2014) Malebo, Hamisi M.; Kihampa, Charles; Mgina, Clarence A.; Sung’hwa, Fortunatus; Waibel, Reiner; Jonker, Stephan A.; Nkunya, Mayunga H. H.
    Phytochemical investigation of Sanrafaelia ruffonammari Verd and Ophrypetalum odoratum Diels that belongs to the rare genera confined to East African coastal forests led to the isolation of enantiomeric styrylpyrone dimer, (±)-5-methoxy-7-phenyl-[4-methoxy-2-pyronyl]-1-(E)-styryl-2-oxabicyclo-[4.2.0]-octa-4-en-3-one (1) alongside (+)-6-styryl-7,8-epoxy-4-methoxypyran-2-one (2) and the enantiomeric (+)- (3) and (-)-6-styryl-7,8-dihydroxy-4-methoxypyran-2-ones (4). Their structures were established by means of spectroscopic methods. In this paper we reveal for the first time the occurrence of styrylpyrones in East African biodiversity. (+)-6-Styryl-7,8-epoxy-4-methoxypyran-2-one (2) and the dihydroxystyrylpyrone enantiomer (3) showed in vitro antifungal activity against Candida albicans at a concentration of 24.4 and 26.2 µM with zones of inhibition of 17 and 9 mm, respectively. Compound 2 exhibited strong activity in the brine shrimp test with LC50 = 1.7 µg/mL. Their high cytotoxic and antifungal activities render them candidates for further scientific attention for drug development programs against cancer and microbial infections.
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    Bio-recognition Ability of Polysaccharides as Piezo Quartz Biosensors
    (2012) Kalmykova, E. N.; Mgina, Clarence A.
    Piezoquartz biosensors (PQB) which are analytical devices for recognition of biochemical interactions have recently attracted increasing interest from different researchers such as analysts, immune-chemists, medical doctors, environmentalists, etc. This is due to the advantages of PQB for having high detection sensitivity (at ng and mg level depending on the mass of sorbates or micro-organisms) and the ability to monitor biochemical reactions in turbid or highly coloured liquids (including in biological fluids) in real time. The use of additional markers and preliminary sample preparation are not required in this biorecognition process. This paper reports on the principle of the PQB and the design units to perform analysis in static and dynamic conditions using different types of biomolecules (immunoglobulins, DNA, lipopolysaccharides, glycoconjugates, hapten-protein conjugates and polysaccharides). Research results performed at the Department of Chemistry, Lipetsk State Technical University (Russia) and School of Physics, College of Natural Sciences, UDOM (Tanzania) are presented. The report aims to review various examples of use of carbohydrate molecules and glycoconjugates in the design of the PQB. These examples include the following: use of sulphated polysaccharides to increase the strength of the sensor’s bio-laye;, use of glycolipids such as O-antigens of bacteria (Yersinia enterocolitica) with different chemical structures in the development of immunosensors for the determination of specific immunoglobulins at 3-100 mg/ml levels in serum; and the use of polysaccharide hydrogels of the first chemical structure (hyaluronic acid, zosteran and neutral and acidic polysaccharide fractions isolated from water hyacinth Eichhornia crassipes) in studying their effectiveness in Pb2 + ions sorption.
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    Composition of Non Volatile Oils and Antimicrobial Activities of Extracts from Monanthotaxis Discolor, and an Undescribed Uvariondedron Species
    (2012) Sumary, Dominic; Mgina, Clarence A.; Joseph, C. C.
    The chemical compositions of non volatile oil extracts from two Annoneceous plant species Monanthotaxis discolor and an undescribed Uvariodendron species which are endemic to Eastern Arc Mountains, Tanzania were determined by GC-MS. The biological activities of extracts and fractionated samples were also determined. Both methanol and dichloromethane extracts of the root bark of M. discolor showed mild antimicrobial activity and had positive brine shrimp test (BST). The BST test for dichloromethane extract of M. discolor root bark were LC50 41.794 µg/ml and that of methanol extract showed LC50 13.560 µg/ml. The petroleum ether and dichloromethane extracts of root bark of Uvariodendron species showed cytotoxicity of LC50 33.06 µg/ml and LC50 35.35 µg/ml, respectively. Twelve major constituents were identified from the dichloromethane extract of M. discolor root bark of which the following compounds were in high composition; α- cadinol (42.85%), (-)-alloaromadendrene (11.7%) aristolone (10.57 %), γ-cadinene (8.72%), δ- cadinene (3.44%) and cubenene (2.28%). The Second fraction of the third repeated column chromatography from the VLC fraction of dichloromethane extract and the first fraction of the VLC of methanol extract root bark revealed, among others 23 components of which the most abundant were; (-)-alloaromadendrene (15.1%), T-cadinol (8.08%), chamigren (5.3%) and γ- Cadinene (5.1%). Other components were also identified from other methanol fractions; (+)- aromadendrene, (18.2%), (-)-alloaromadendrene (12.8%), 4,9-muurodiene (5.3%), T-cadinol (83%), ς-himachelene (0.63%) and ledol (0.3%). The ethanol:dichloromethane (1:1) extract of the leaves of M. discolor showed four different components from those identified from root bark extracts among which heptacosane and tributylamine had percentage composition of (3.42%) and (0.34%),.respectively. The petroleum ether extract of the root bark of the undescribed Uvariodendron species revealed seven components of which the most abundant were methyl eugenol (38.7%) and elemicin (18.2%). For the ethanol extract of stem bark oil mixtures the most abundant components were δ-cadinol (0.25%), methyl eugenol (0.12%), isoelemecene (0.04%), and diisooctyphthalate (0.02%).
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    In Vivo Antiviral Activity, Protease Inhibition and Brine Shrimp Lethality of Selected Tanzanian Wild Edible Mushrooms
    (2010-07) Kidukuli, Abdul W.; Mbwambo, Zakaria H.; Malebo, Hamisi M.; Mgina, Clarence A.; Mihale, Matobola J.
    In endeavor to have detailed account of nutritional, medicinal and pesticidal potentials of Tanzanian wild mushrooms, a study was conducted to assess the antiviral and protease activities of five edible species: Cantharellus platyphyllus and C. isabellinus from genus Cantharellus and Pleurotus djamour, P. sajor-caju and P. citrinopileatus from genus Pleurotus. Methanolic extracts were subjected to cytotoxicity lethality tests against Artemia salina Leach according to Meyer et al., (1982), in vivo antiviral tests using embryonated chicken eggs and protease tests using Screen to Nature methods. C. platyphyllus extracts had the highest cytotoxicity activity among Cantharellus species (LC50 = 7.846 ?g/ml) and of all tested species. P. citrinopileatus extracts had highest cytotoxicity (LC50 = 12.807 ?g/ml) among Pleurotus species. C. isabellinus and P. djamour extracts had stronger antiviral activities against both pox virus and infectious bursa disease virus. Other tested mushrooms showed moderate antiviral activities. All tested species showed non protease activities. While the Cantharellus species showed no protease inhibition property, Pleurotus species inhibited protein degradation similar to protease inhibitor. From these observations, the use of mushrooms as food and therapeutic substances particularly in HIV/AIDS infected persons is highly encouraged. It is recommended that further studies involving detailed biological activities (including antimicrobial, antioxidant and pesticidal activities) and determination of chemical compositions of Tanzanian wild edible mushrooms be done as the knowledge will contribute to the existing knowledge on these useful macro fungi.
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    Ophrypetalin and Other Annonaceous Acetogenins From Ophrypetalum Odoratum
    (Taylor and Francis, 1999-05) Sung'hwa, Fortunatus; Mgina, Clarence A.; Jonker, Stephan A.; Nkunya, Mayunga H. H.; Waibel, Reiner; Achenbach, Hans
    Ophrypetalin, a new bis-tetrahydrofuran acetogenin, was isolated from Ophrypetalum odoratum (Annonaceae) together with the known acetogenins desacetyluvaricin, rolliniastatin-1, dieporeticenin and a mixture of dieporeticanin-1, dieporeticanin-2, and diepoxyrollin. the structures were elucidated by spectroscopic methods. the absolute configurations were established by Mosher's method and by CD measurements.