Browsing by Author "Manoko, Mkabwa L.K."

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    Selenium Accumulating Leafy Vegetables Are a Potential Source of Functional Foods
    (Hindawi Publishing Cooperation, 2015) Mabeyo, Petro E.; Manoko, Mkabwa L.K.; Gruhonjic, Amra; Fitzpatrick, Paul A.; Landberg, Göran; Erdélyi, Máté; Nyandoro, Stephen S.
    Selenium deficiency in humans has been associated with various diseases, the risks of which can be reduced through dietary supplementation. Selenium accumulating plants may provide a beneficial nutrient for avoiding such illnesses. Thus, leafy vegetables such as Amaranthus hybridus, Amaranthus sp., Cucurbita maxima, Ipomoea batatas, Solanum villosum, Solanum scabrum, and Vigna unguiculata were explored for their capabilities to accumulate selenium when grown on selenium enriched soil and for use as a potential source of selenium enriched functional foods. Their selenium contents were determined by spectrophotometry using the complex of 3,3󸀠-diaminobenzidine hydrochloride (DABH) as a chromogen. The mean concentrations in the leaves were found to range from 7.90 ± 0.40 to 1.95 ± 0.12 𝜇g/g dry weight (DW), with C. maxima accumulating the most selenium. In stems, the accumulated selenium content ranged from 1.12 ± 0.10 𝜇g/g in Amaranthus sp. to 5.35 ± 0.78 𝜇g/g DW in C. maxima and was hence significantly different (𝑃 < 0.01). The cancer cell line MDA-MB-231 was used in cytotoxicity assays to determine the anticancer potential of these extracts. With exception of S. scabrum and S. villosum, no cytotoxicity was detected for the selenium enriched vegetable extracts up to 100 𝜇g/mL concentration. Hence, following careful evaluation the studied vegetables may be considered as selenium enriched functional foods.
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    Trace Element Concentrations in Soil, Sediments, and Waters in the Vicinity of Geita Gold Mines and North Mara Gold Mines in Northwest Tanzania
    (Taylor & Francis, 2012) Åsgeir, Ålmås R.; Manoko, Mkabwa L.K.
    The “Geita Gold Mine” (GGM) and “North Mara Gold Mines” (NMGM) have devel- oped large quarries in the middle of fertile agricultural lands. Possible hazardous impact on the natural recourse has warranted a study on the trace element concentrations in soils, sediments, and natural waters. Generally, the study shows a great variation in type of elements and intensity of their spill to soils, sediments, and waters. We found indications of acid mine drainage (AMD) of trace metals near the GGM waste rock tailings, but the data are inconclusive. The environmental impact at NMGM was, on the other hand, more extensive. Severe trace element contamination of sediments and waters near one of the mining facilities managed by NMGM is connected to an accidental acid spill in 2009. However, we found strong indication that, in addition to the accident, leakage of alkaline wastewater into surface soils and free water took place from a large wastewater reservoir. We found very high concentrations, especially of As in sediments and water samples downside this reservoir. Water from several sites contained As con- centration in the free water at more than one order of magnitude higher than the WHO drinking water recommendations. The chemical speciation of water samples indicated high fraction of Free Ion Activity (FIA) in several samples and the change in pH had a significant impact on the FIA. Due to extensive alkaline and acidic runoff from these sites, more information about hydrological transport routes and the chemical speciation of the free water is of great importance for assessing potential risk of these mines.