1,868 research outputs found

    Phytochemical and antimycobacterial studies on selected medicinal plants

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    Tuberculosis (TB) is an infectious disease caused by the pathogen Mycobacterium tuberculosis. Tuberculosis was first declared as a global health emergency in 1993 but is still a health crisis worldwide because of the emergence of extensively drug-resistant strains of M. tuberculosis coupled with the increased risk of infection in immune-compromised people and also by the fact that at least one third of the human population are latently infected with the TB causing bacilli. New, safer and more effective antimycobacterial compounds with novel mechanisms of action are urgently needed for treating resistant forms of tuberculosis. This has led to a renewed research interest in natural products, which offer an outstanding source of diverse bioactive chemical scaffolds with the hope of discovering novel anti-mycobacterial leads. This thesis describes phytochemical studies on the genera Allium and Andrographis. The antibacterial activity of the crude extracts, various fractions and isolated compounds were evaluated. Antibacterial studies were carried out using a panel of Gram-positive, Gram-negative and acid fast group of bacterial species including M. aurum, M. bovis BCG, M. tuberculosis H37Rv and multidrug-resistant clinical isolates of M. tuberculosis. Furthermore, analogues of naturally isolated disulfides from the genus Allium were synthesized and evaluated for antibacterial activity. Eukaryotic cytotoxicity was estimated in order to determine the therapeutic selectivity index of the selected compounds. In addition, inhibition of both drug efflux and biofilm formation was observed at the whole-cell phenotypic level. These analogues have demonstrated anti-TB activity with the lowest MIC being 4 mg/L. They also exhibited whole cell multidrug efflux and biofilm inhibitory effect. These findings would serve as useful contribution to the development of novel anti-TB drugs

    Listen to the Story: Banksy, Tyler the Creator, and the Growing Nihilistic Mindset

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    Art, as an expression of feelings, worldviews, and personal beliefs, is a reflection of our environment and how we interact with it. In this way, urban art such as rap music and graffiti can serve as a lens through which we are able to examine the state of the urban environment. Building on community literature that addresses the presence of nihilism in rap music, this work will establish that nihilism is a prevalent theme in the work of two artists: Tyler the Creator\u27s rap music and BANKSY\u27s graffiti art. By examining the growing subculture and appeal of urban art in relation to these two artists, this paper will argue that BANKSY and Tyler the Creator belong to a new wave of urban art, one that appeals to and originates from people of all races and classes. The current work will then examine these artists\u27 motives in including nihilism within their art in order to argue that the disillusionment and nihilism once found primarily within inner cities is now spreading to new frontiers. Using this analysis, the current work will raise questions as to the possible causes and consequences of this spreading nihilistic mindset

    The characterisation of actinomycetes isolated from diverse South African sources, with emphasis on the genus Kribbella

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    Includes abstract.Includes bibliographical references (p. 169-171).Actinomycetes were isolated from the leaves of indigenous plants, aquatic sediment and soil samples, using alternative isolation methods to select for actinomycetes belonging to the rarer genera. Thirty actinomycete strains belonging to the genera Gordonia, Kineococcus, Kribbella, Micromonospora, Nocardia and Streptomyces were selected for full characterisation. A polyphasic approach combining physiology, chemotaxonomy and phylogenetic analysis was used to characterise these isolates. A number of potentially novel strains belonging to the rarer genera were identified, including two Kineococcus and three Micromonospora strains. Two novel Kribbella species were isolated from soil samples and the species descriptions of Kribbella karoonensis Q41T and Kribbella swartbergensis HMC25T were published in 2006

    Evaluation of the Plant Extracts of an Anti-Tubercular Herbal Remedy

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    Ximenia americana root bark (Olacaceae) and Pavetta crassipes (Rubiaceae) leaf used in Nigerian traditional medicine were tested individually against clinical isolate of Mycobacterium tuberculosis by Lowenstein - Jensen method. Crude aqueous extracts of X. americana and P. crassipes exhibited minimum inhibitory activity (MIC) of 100 μg/mL and 200 μg/mL respectively. Sequential screening with solvents of different polarities was used in evaluation tests to readily locate the source of the activity against tuberculosis and for conditions related to skin diseases since it was readily available. In general, antimicrobial screening of crude extracts gave MICs ranging from 31.25 μg/mL to > 5 mg/mL, with X. americana methanol extract being most active at 31.25 μg/mL against Staphylococcus aureus. In an effort to determine possible mechanisms of action, synergistic interaction studies between standard antibiotics and plant extracts were carried out with some synergy being observed between X. americana extract and streptomycin. Hexane (MIC 60.6 μg/mL) and dichloromethane (MIC 30.5 μg/mL) fractions of X. americana exhibited 94.3 % and 96.4 % inhibition against M. tuberculosis H37HRv (virulent strain) while P. crassipes hexane fraction had 86.7% inhibition at > 64 μg/mL. Using HPLC, TLC, GC, 1D and 2D-NMR as well as mass spectral analyses it was possible to identify rutin and 5-O- caffeoyl quinic acid methyl ester from P. crassipes. It proved extremely difficult to identify compounds from LC and TLC fractions from the non-polar extracts of X. americana responsible for anti-TB activity. There was some spectroscopic evidence from these fractions for closely related phytosterol esters and individual compounds such as stigmast- 3, 5 - diene, stigmastane oleate and β-sitosterol. Subsequent LC work with refractive index detection and SFC with evaporative light scattering data confirmed that the difficulties in assignment arose from the presence of non-UV absorbing non-volatile co-eluting compounds. Preparative xviii SFC or SFC-MS with the aid of the NIST database would have been needed for identification. Overall, these results lend some credence to the claims of the Nigerian remedy and potentially could be a source of assay biomarkers for monitoring its safety, efficacy and quality as required by IRCH (International Regulatory Co-operation for Herbal Medicines)

    Isolation and characterization of antiplasmodial compounds from Siphonochilus aethiopicus and Aloe ferox and bioavailability of a novel furanoterpenoid

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    Includes abstract. Includes bibliographical references (leaves 138-162)

    A new perspective on Einstein's philosophy of cosmology

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    The recent discovery that Einstein once attempted - and quickly abandoned - a steady-state model of the expanding universe sheds new light on his philosophical journey from static to dynamic cosmologies.Comment: Revised book chapter. To be published in 'The Philosophy of Cosmology:Foundations and Perspectives'. Eds J.Silk and J.Barrow (Cambridge University Press

    Identifying Requirements in Microservice Architectural Systems

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    Microservices and microservice architecture has grown popularity and interest steadily since 2014 but many challenges are still faced in a software project when trying to adopt the concept. This work gathers challenges, possible solutions, and requirements related to the use of microservice architecture and therefore support the work of different stakeholders in a software project using microservice architecture, while also providing more information to the research as well. The study was conducted using systematic literature review (SLR). Overall, 63 scientific publications from four different scientific databases were selected and analysed. As a result, rapid evolution, life cycle management, complexity, performance, and a large number of integrations were identified as the most common challenges of microservice architecture. Solutions such as service orchestration, fog computing, decentralized data, and use of patterns were proposed to tackle these challenges. Regarding requirements, scalability, efficiency, flexibility, loose coupling, performance, and security appeared most frequently in the literature. The key finding of this work was the importance of data. How data acts as a base for functionalities and when inaccurate can cause complex challenges and make functionalities worthless. Based on this, we have a better understanding on what challenges may occur and what to focus on while working with microservice architecture in software development

    Characterization of mycobacteria SPP. and antimycobacterial activities of plant derived compounds from Anacardiaceae family

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    The treatment of tuberculosis (TB) is currently a challenge due to multi- and extensively drug resistant strains of Mycobacterium tuberculosis. Mycobacterium bovis and M. tuberculosis cause clinically indistinguishable tuberculosis in humans. Both M. bovis and M. tuberculosis have been isolated from humans and animals. Plant species contain antimicrobial compounds that may lead to new anti-TB drugs. To conduct in vitro antimycobacterial assays, it is important to include current clinical isolates as new strains of bacteria might be circulating under the ongoing climate change environment. The overall goal and objectives of this study were to isolate and characterize mycobacteria species from South Africa, to test some selected plant species of the Anacardiaceae family for antimycobacterial activity using some of the newly isolated and reference strains of mycobacteria followed by cytotoxicity evaluation of the most active plant species, and finally the isolation and characterization of at least one compound from the most active and least toxic plant. This study led to the discovery of a new isolate of Mycobacterium Avium Complex species from black wildebeest. Other non-tuberculous mycobacteria and M. bovis isolates were identified from other animal species. Five out of 15 plant species screened showed good activity against Mycobacterium species. Five antimycobacterial compounds were isolated from Searsia undulata, the most active plant species. Two out of the five compounds were identified, and one compound appears to be novel, but both compounds have been isolated for the first time from Searsia undulata. An incidental finding was the potential anticancer property of extracts of Searsia undulata. Recommended future activities include isolation and identification of more active compounds from Searsia undulata which were visible in bioautography analysis, as well as synergy evaluation of antimycobacterial activities of the different compounds with current anti-tubercular drugs.Environmental SciencesPh. D. (Environmental Science
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