Browsing by Author "Dushimemaria, Florence"

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    Antimicrobial and antiplasmodial activity displayed by actinomycetes isolated from soils from Kavango and Hardap regions in Namibia
    (2018) Iikasha, Albertina M.; Dushimemaria, Florence; Mbewe, Maria; Eiman, H.; Mumbengegwi, Davis R.
    Plasmodium falciparum and multidrug resistant bacteria such as Mycobacterium avium, Staphylococcus aureus and Escherichia coli are among the top causes of morbidity and mortality especially in developing countries. These pathogens are responsible for the reported antibiotic resistance incidents globally. Due to the increase in antibiotic resistance worldwide, there is an urgent need for new bioactive compounds. This study aimed at determining the antiplasmodial and antimicrobial activity of secondary metabolites produced by soil actinomycetes. Soil samples were collected from Kavango and Hardap regions and cultured on various media to isolate and identify actinomycetes. Secondary metabolites produced were extracted using different solvents. The antimicrobial activity of different isolated secondary metabolites was determined against M. avium, S. aureus and E. coli. Antiplasmodial activity of four bioactive fractions with potent antibacterial activity was further determined against a chloroquine resistant (D10) P. falciparum strain at various concentrations. Bioactive compounds from two isolates displayed activity against M. avium, whilst another two showed activity against E. coli. None of the secondary metabolites displayed activity against S. aureus. A concentration dependent reduction in parasitaemia for P. falciparum was observed across all four fractions both after 24 and 48 h. These results display a vast potential antibacterial and antiplasmodial activity and should be considered for future drug development.
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    Indigenous knowledge of medicinal plants used for the treatment of cancer
    (University of Namibia Press, 2015) Dushimemaria, Florence; Mumbengegwi, Davis R.; Bock, Ronnie A.
    The global burden of cancer continues to increase in both developed and developing countries. This is largely attributed to a growing aged population as both the numbers of people and life expectancies increase. Another important factor is the adoption of lifestyles that increase the risk of developing cancer (Jemal et al., 2011). Lifestyle choices, such as smoking tobacco, consuming alcohol, being physically inactive and eating unhealthily, contribute to the upsurge in cancer cases. Siegel, Naishadham and Jemal (2012) estimated that about 1,638,910 new incidences of cancer and about 577,190 deaths due to cancer occurred worldwide in 2012. They further estimated that 56% of the cancer cases and 64% of cancer-related deaths occurred in developing countries (Jemal et al., 2011), indicating that the developing world is gradually having to shoulder more of the burden and where cancer survival rates tend to be lower.
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    An investigation into the antineoplastic properties of Schinziophyton Rautanenii and Colophospermum mopane
    (2014) Dushimemaria, Florence
    Cancer incidences are on the rise in Namibia, because of late diagnosis, cancer cases often have poor prognosis and treatment options are limited especially in resource poor rural settings. Ethnomedicinal plants present a treatment option which is used in such settings, is accessible and inexpensive. However evidence on safety and efficacy of these traditional medicinal plants is lacking, which prevents mainstream use. This study evaluated two Namibian indigenous plants, Schinziophyton rautanenii and Colophospermum mopane used medicinally in Zambezi region, for their phytochemical content and anti-protease activity. Furthermore, phytochemicals where quantified as percentage yields of dry plant material, antioxidant activity measured and plants were evaluated in vitro for anti-cancer activity against breast, renal and melanoma cancer cell models. Additionally, plant extracts were screened against a human fetal lung fibroblast cell line to determine cytotoxicity. Extracts were also assayed in vivo in Planaria, for toxicity. Alkaloids, coumarins, flavonoids and triterpenes were found in all plant extracts, except anthraquinones which were only found in the root extract of S. rautanenii. Antioxidant activity shown by plant extracts was in correlation with the observed alkaloid content of plants, (correlation =0.58, n=12, p=0.048). The highest in vitro anticancer activity was exhibited by the organic root extract of C. mopane, with IC50 48.2 μg/ml although it also showed mild cytotoxicity against fibroblast cells, IC50 162.4 μg/ml. In vivo toxicity evaluation further revealed the strong toxicity level of the organic C. mopane root extract against the freshwater flatworm planaria at 20 μg/ml. The aqueous bark and root extracts of C. mopane showed some anticancer activity towards the breast cancer model (IC50 86.8 μg/ml and 87.9 μg/ml respectively) while the organic bark and root extracts of C. mopane showed anticancer activity against a melanoma (IC50 92.5 μg/ml and 64.1 μg/ml), breast (IC5070.2 μg/ml and 48.2 μg/ml ) cancer models respectively. The melanoma cell line UACC-62 displayed sensitivity towards the aqueous bark and root extracts of S. rautanenii with low IC50 values of 116.7 μg/ml and 128.7 μg/ml respectively. The organic root extract of S. rautanenii also showed sensitivity towards the UACC-62 melanoma cell line at high extract concentration although IC50 102.6 μg/ml, was similar to that obtained against MCF-7 breast cancer cells, 102.4 μg/ml. The organic and aqueous root extracts of S. rautanenii displayed the highest IC50 values of 315.5 μg/ml and 444.8 μg/ml against the human fetal lung fibroblast cell. In conclusion, the use of C. mopane and S. rautanenii within the traditional settings is rational and a readily accessible alternative. However, further studies are required to assess the extent of toxicity before the extracts can be recommended for mainstream usage.
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    Rondomized anticancer and cytotoxicity activities of Guibourtia Coleosperma and Diospyros Chamaethamnus
    (2017) Dushimemaria, Florence; Du Preez, Iwanette C.; Mumbengegwi, Davis R.
    Background: Plants have consistently proven to be a reliable and yet not fully explored source of medicines. In light of this, there is a constant demand for new treatment regimens for cancer. Namibia has a rich diversity of plant species of over 4300 with 17 % of them being endemic to Namibia. Plants growing in Namibia’s diverse climatic zones produce many secondary metabolites as part of adaptation to their environment. This article focused on the screening of such phytochemicals and their cytotoxic and anticancer properties in vitro. Two Namibian plants Diospyros chamaethamnus and Guibourtia coleosperma were randomly selected for this purpose. Materials and Methods: The plants were screened for the presence of coumarins, alkaloids, flavonoids, anthraquinones, steroids and terpenoids using thin layer chromatography. Anticancer screening was performed on a panel of three cancer cell lines, while cytotoxicity was determined using a human fibroblast cell line, both using the SRB method. Results: Alkaloids, anthraquinones, flavonoids and steroids were detected in both organic and aqueous extracts of the two plants. The organic plant extracts had a greater anti-proliferative effect on the cancer cell lines than the aqueous extracts; the D. chamaethamnus organic root extract was the most potent with an IC50 of 16.08, 29.12 and 24.67 μg/mL against TK10, UACC62 and MCF7 cells, respectively. Furthermore, cytotoxicity analysis revealed the non-toxic nature of the extracts, except for the organic root extract of D. chamaethamnus that showed significant cytotoxicity (IC50 13.03 μg/mL). Conclusion: D. chamaethamnus is a potential candidate for the development of a plant based cancer treatment. The study showed the value of random screening in drug discovery from plants for pharmacological activity that is unrelated to their ethnomedicinal uses.
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    The use of traditional medicinal plants as antimicrobial treatments
    (University of Namibia Press, 2015) Mumbengegwi, Davis R.; Du Preez, Iwanette C.; Dushimemaria, Florence; Auala, Joyce R.; Nafuka, Sylvia N.
    Microbial infections are a major cause of morbidity and sometimes mortality, especially in developing countries such as Namibia. Severe poverty is the root cause of this undesirable situation as it leads to malnutrition, inadequate sanitation and consumption of unclean food and drink. This, compounded by lack of education and access to primary healthcare, results in infections by microorganisms such as viruses, bacteria, fungi and protozoa (Table 4.1). The most vulnerable to infectious diseases caused by microbial agents are children under the age of five, where 66% of deaths in this age group are a result of such diseases; 34% of all deaths are attributed to infectious diseases. This was underscored by WHO’s (World Health Organization’s) Regional Director for Africa, Luis Gomes Sambo, in 2011 when he said 63% of deaths on the continent were caused by microbial infections, with HIV/AIDS accounting for 38.5% of these (Anon, 2012). Thus, the most vulnerable groups are young children and individuals whose immune systems are compromised by HIV infection (Table 4.2). Community-acquired bacteraemia is a major cause of death in children at rural sub-Saharan district hospitals. A study by Berkley et al. (2005) showed that 12.8% of infants younger than 60 days had bacteraemia. Escherichia coli and group b streptococcus were the predominant infectious agents.