Browsing by Author "Du Preez, Iwanette C."

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    Ethnopharmacological assessement of Guibourtia Coleosperma and Diospyros Chamaethamnus extracts as elaternative treatment options for Malaria
    (University of Namibia, 2016) Du Preez, Iwanette C.
    Malaria, a parasitic infectious disease, remains one of the world’s foremost health concerns, even more so in developing countries. Much progress has been made in fighting the disease, particularly in Southern Africa where four countries (Namibia included) have targeted malaria elimination by 2020. Challenges such as the absence of a vaccine, resistance to insecticides, and particularly the emergence of resistance to current antimalarial treatment regimens threaten to undermine the current successes in malaria control efforts. Secondly, the lack of access and acceptance of conventional antimalarial treatment by populations in malaria endemic areas reduces the feasibility of eliminating and consequently eradicating malaria. Local communities in Namibia use plant-based medicines to treat malaria and malaria associated symptoms based on traditional observations or beliefs over decades. As to whether these plants are efficacious for the indication and cause toxicity is yet to be validated scientifically. The aims of this study were, therefore, to evaluate the biological activities of the extracts of two Namibian plant species to provide a scientific rationale for their traditional uses. Guibourtia coleosperma and Diospyros chamaethamnus, which are used to alleviate symptoms of malaria in Namibia, were investigated using phytochemical analyses, and in vitro and in vivo bioassays. Extracts were prepared by using solvent extraction of varying polarities to obtain a wide range of metabolites. Ground plant material was macerated in distilled water (aqueous extracts) and dichloromethane-methanol (1:1v/v) (organic extracts) respectively. The extracts were dried in vacuo, and examined for six classes of compounds known to have antiplasmodial activity using TLC. GC-MS was used to identify compounds in the plant extracts related to biological activity, using a BP5MS column. Radical scavenging abilities of the plant extracts were ascertained by the 2,2-Diphenyl-1-picrylhydrazyl (DPPH) method. In vitro antimalarial activity was determined by reconstituting the plant extracts in water and DMSO at varying concentrations, and incubating extracts with Plasmodium falciparum D10 infected RBCs for 48 hours. Subsequently, growth inhibition of the P. falciparum parasites was determined using parasitaemia. In vitro assays to determine cytotoxic effects were conducted with the plant extracts using a fibroblast cell line (W138). In vivo inhibition of the growth of P. berghei in Swiss albino mice (20±4 g) was evaluated using optical microscopy on blood smears. Survival curves post-infection were also used to determine suppressive and prophylactic activities of extracts. The plant extracts were also evaluated for their toxicity in healthy mice using a dose escalation method with a starting dose of 300 mgkg-1. The crude extracts contained alkaloids, anthraquinones, flavonoids, steroids and terpenoids. Secondary metabolites with antiplasmodial, antibacterial and antioxidant properties were tentatively identified as 3,5-dihydroxy-6-methyl-2,3-dihydro-4H-pyran-4- one, phloroglucinol, stigmasterol, glycerol 2-hexadecanoate, α-amyrin, 9,12-octadecdenoic acid (Z,Z)-, hexadecanoic acid, oleic acid, lanosterol, spiculesporic acid, squalene, campesterol and vitamin E. Antioxidant activity results showed that the extracts of D. chamaethamnus yielded the highest antioxidant activities with IC50 values of ranging from 7.63 to 10.74 μg/mL, whilst the extracts G. coleosperma yielded antioxidant activities with IC50 values of ranging from 22.03 to 36.05 μg/mL. Moderate in vitro antiplasmodial activity (IC50 < 50 μg/ml) against P. falciparum D10 was observed for the two plants ranging from 18.30 to 31.61 μg/mL. All plant extracts showed no cytotoxicity with IC50 values above 100 μg/mL, except for the organic extract of D. chamaethamnus (CC50=29.73). The organic extracts for both D. chamaethamnus and G. coleosperma (800 mgkg-1) exhibited significant (P< 0.05) blood schizonticidal activity in the 4-day early infection test with parasite growth inhibition of 44.66 and 29.59 %, respectively. This dose also prolonged the survival of the mice by 50 and 58 % (i.e. with 6 and 7 days), respectively. The plant extracts also exhibited prophylactic activity in the mice inhibiting parasitaemia with 56.13 (D. chamaethamnus) and 55.48 % (G. coleosperma) at the highest dose (800 mgkg-1) and increasing survival by 155.6 and 22.2 % (i.e. with 14 and 3 days), respectively. Oral administration of crude extracts at the highest dose of 2000 mgkg-1 resulted in no mortalities or evidence of adverse effects, indicating that D. chamaethamnus and G. coleosperma extracts were non-toxic. The study showed promising antimalarial activities of D. chamaethamnus and G. coleosperma. The results show that the ethnomedicinal use of these plants to treat symptoms of malaria is rational and safe. This is a step in the right direction towards incorporating their use in mainstream health care policies as alternative treatment options for malaria. Identification of bioactive compounds to standardize extracts should the next step. Further studies should also include the optimization of doses to improve efficacy, and studies to assess the antiplasmodial activities of the two plants in combination treatments as used in an ethnomedicinal setting. Lastly, this study has shown that the plant extracts can also be used as a prophylactic. This is new knowledge should be shared with indigenous communities to maximize the medicinal use of these plants.
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    Evaluation of the Antiplasmodial Properties of Namibian Medicinal Plant Species, Moringa ovalifolia
    (2017) Du Preez, Iwanette C.; Bussel, Rahl-Jeanne; Mumbengegwi, Davis R.
    Background and Objective: Malaria is a major cause of morbidity and mortality in Sub-Saharan Africa but it is on the decline in some Southern African countries including Namibia, which is moving towards elimination of the disease. Despite the availability of effective medicines in Namibia, some communities do not accept allopathic medicines, preferring traditional medicines. This study was conducted to determine the phytochemistry and the efficacy of Moringa ovalifolia (M. ovalifolia ) an ethnomedicinal plant, to provide a basis for their integration into mainstream malaria case management. Materials and Methods: Moringa ovalifolia was screened for known classes of antimalarial phytochemicals using thin layer chromatography. In vitro antiplasmodial activity of aqueous and organic extracts from Moringa ovalifolia was measured using parasitaemia post-treatment with plant extracts as well as the IC50 values. Data analysis using two-way ANOVA to determine the significant interactions between plant extracts and plasmodic growth. Results: Phytochemical screening of M. ovalifolia revealed the presence of flavonoids, anthraquinones, coumarin, terpenoids and alkaloids. Against Plasmodium falciparum (P. falciparum) D10, the leaf extracts of M. ovalifolia were the most effective with IC50 values of 14.30 and 20.73 μg mLG1 for the organic and aqueous extracts, respectively. Conclusion: M. ovalifolia extracts exhibited moderate antiplasmodial properties in vitro and have potential as antimalarials. These findings provide a basis for further investigation into their phytochemistry as well as in vivo studies on their safety and efficacy to support their use as an alternative treatment for malaria.
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    Immunomodulatory effects of some Namibian plants traditionally used for treating inflammatory diseases
    (Ethnopharmacology, 2020) Du Preez, Iwanette C.
    Ethnopharmacological relevance: Acanthosicyos naudininus, Gomphocarpus fruticosus, and Cryptolepis decidua are, according to the knowledge of traditional healers, used in Namibia to treat inflammatory disorders such as pain, fever and skin rashes. Aim of the study: The present study was conducted to evaluate the immunomodulatory effects and the possible underlying mechanisms of action of the plant extracts on peripheral blood mononuclear cells (PBMCs) such as T-lymphocytes. Materials and methods: Methanolic and EtOAc extracts of A. naudinianus, G. fruticosus and C. decidua were analysed for their immunomodulatory potential. PBMCs were isolated from the blood of healthy donors and incubated with the plant extracts at concentrations 100, 30, 10, 3, 1 and 0.3 μg/mL. Effects on proliferation and viability of activated human lymphocytes were assessed in comparison to ciclosporin A by flow cytometry using carboxyfluorescein succinimidyl ester (CFSE) and WST-1 assay. Flow cytometry by annexin V/propidium iodide (PI) staining was performed to investigate the necrotic/apoptotic effect of the plant extracts on mitogen-activated human lymphocytes. In addition, analysis of the influence of plant extracts on the regulatory mechanisms of T-lymphocytes was performed using activation marker and cytokine production assays. An HPLC-PDA-ELSDESIMS profile was recorded for each of the extracts. Results: T-lymphocyte proliferation was inhibited in a dose-dependent manner by the extracts of A. naudinianus, G. fruticosus, and C. decidua in concentrations not causing apoptosis or necrosis. This effect was mediated by inhibition of lymphocyte activation, specifically the suppression of CD25 and CD69 surface receptor expression. Moreover, the extracts suppressed effector functions, as indicated by reduced production of IFN-γ and IL-2. Based on the HPLC profile, possible responsible compound classes could be identified for the extracts of A. naudinianus (cucurbitacins) and C. decidua (indole alkaloids), but not for G. fruticosus. Conclusions: The data show that the extracts of A. naudinianus, G. fruticosus and C. decidua have in vitro immunomodulatory activity and they interfere with the function of immunocompetent cells, suggesting an antiinflammatory mode-of-action. The present chemical determination and pattern recognition results explain the therapeutic potency. However, further studies to investigate the therapeutic potential of the plants in inflammatory disorders should be done.
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    Phytochemical investigation on Namibian plants for anti-malaria compounds
    (University of Namibia, 2012) Du Preez, Iwanette C.; Mumbengegwi, Davis R.
    Malaria is on the decline in Namibia due to interventions by the Ministry of Health and Social Services (MoHSS) and the country is moving towards pre-elimination of the disease. However, barriers such as resistance of the uptake of interventions by "at risk" communities, e.g. lack of treatment seeking behavior for WHO recommended ACT's exist. Some communities in malaria-endemic areas do not accept Western medicine, preferring traditional medicines as prescribed by traditional healers. It is important to balance people's cultural beliefs and practices with the MoHSS's objective of malaria elimination by 2020. To facilitate integration of traditional treatments into mainstream malaria case management, documentation and validation of the treatments to allow their safe and effective use have to be carried out. This study was conducted to document and validate the use of seven plants native to Namibia, targeted on the basis of their indigenous uses which suggest their toxicity to Plasmodium parasites. Crude extracts were prepared using methanol-dichloromethane (1/1V/V) and distilled water at 60 C. The extracts were further Partitioned with chloroform-methanol water (12/6/lV/V). Preliminary phytochemical screening was performed to detect the presence of selected Antiplasmodial compounds. Phytochemical tests revealed the presence of anthraquinones, flavonoids, terpenoids, coumarines, and glycosides; alkaloids and steroids were not detected. Paradoxically, thin-layer chromatography analysis on the crude extracts of the same plants tested positive for all compounds. The presence of these phytochemicals and the data generated support the ethno-medicinal uses for these plants
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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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    Study on indigenous medicinal knowledge in Caprivi region
    (2011) Du Preez, Iwanette C.; Nepolo, Emmanuel; Siyengwa, Riina; Shapi, Martin K.; Cheikhyoussef, Ahmad; Mumbengegwi, Davis R.
    SUMMARY: Indigenous knowledge is defined as the uniqe knowledge in a given culture, which is passed on orally from generation to generation (Mapaure & Hatuikulipi, 2007; Dan et al., 2010). This indigenous knowldege is regarded as valuable and considered as the local people’s capital (Mapaure and Hatuikulipi, 2008; Cheikhyoussef et al, 2011), and if not preserved, it may be lost forever to society. The study on Indigenous Medicinal Knowledge in Caprivi region was done in collaboration with the Directorate of Research Science and Technology (DRST) of the Ministry of Education, and was done as a continuing research work for the national survey on Traditional Healing in Namibia. The traditional medical systems are generally based on the uses of natural and local products which are commonly related to the people’s perspective on the world and life (Toledo et al. 2009). Traditional African medicine is 'the sum total of practices, measures, ingredients and procedures of all kinds whether material or not, which from time immemorial has enabled the African to guard against diseases, to alleviate his/her suffering and to cure him/herself' (Busia, 2005). The traditional healing practices in Namibia have been studied by a number of researchers (Shapi et al, 2009; Dan et al, 2010). The aim of this national survey will be to create a database based on the indigenous knowledge of medicinal plants used by traditonal healers and/or knowledge holders to treat a variety of ailments and diseases, as well as for cultural beliefs and practices. As such, the overall aim of this fieldtrip was to interview traditonal healers in the Caprivi region and retrieve as much information as possible with regarding to the uses of medicinal plants, and to collect voucher specimens to be deposited with the National Botanical Research Institute (NBRI), Windhoek, Namibia.
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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.