23 research outputs found
Phytochemical and antimicrobial studies on Rhus natalensis
No full textMagister Scientiae - MScExtracts from the root bark, stem bark, and leaves of R. natalensis were screened for antibacterial activity against standard bacterial strains; Staphylococcus aureas, Escherichia coli and Pseudomonas aureginosa, and fungi; Candida albicans, Trichophyton mentagrophytes or Microsporum gyseum. Chromatographic techniques were utilized to isolate pure compounds. This study validates and documents, in a systematic way, the antimicrobial properties of the R. natalensis used for many years by many people of the world. It also provides valuable information for further phytochemical isolation and characterization studies of active compounds, necessary for the development of new drugs. The extractions were carried out using broad spectrum of solvents (hexane, dichloromethane, ethyl acetate, and methanol). Fractionation was done using standard chromatographic techniques. A total of seven (7) compounds were isolated from R. natalensis. Three of the isolates were characterized and their structures were unambiguously established by detailed spectroscopic analysis that involved high resolution mass spectrometry, 1D and 2D-NMR spectral data experiments 1H, 13C, DEPT, COSY, HMBC, and NOESY. These compounds are: 3-(1-(2,4-dihydroxyphenyl)-3,3-bis(4- hydroxyphenyl)-1-oxopropan-2-yl)-7-methoxy- 4H-chromone-4-one (39), Rhuschromone, a novel compound isolated for the first time, 2’,4’-dihydroxychalcone-(4-O-5’’’)-4’’,2’’’,4’’’- trihydroxychalcone (40) and 3-((Z)-heptadec-13-enyl) benzene- 1,2-diol (41), an urushiol. Compound 39 recorded the highest activity zone of inhibition (21mm) against S. aureas, which was found to be 50% as active the chloramphenicol standard used. The traditional use of the extracts in infections and inflammatory conditions is rationalized based on the content of theisolated compounds, and it has been proposed that the total crude extract, with its contents of so many bioactive compounds, could be formulated for use in many infections, microbial or fungal. Furthermore, not all of the species studied to date have been fully characterized for potential bioactivities. Thus, there remains a significant research gap spanning the range from lead chemical discovery through process development and optimization in order to better understand the full bioactive potential of many of these plants.South Afric
Phytochemical and antimicrobial studies on Rhus natalensis
No full text>Magister Scientiae - MScExtracts from the root bark, stem bark, and leaves of R. natalensis were screened for antibacterial activity against standard bacterial strains; Staphylococcus aureas, Escherichia coli and Pseudomonas aureginosa, and fungi; Candida albicans, Trichophyton mentagrophytes or Microsporum gyseum. Chromatographic techniques were utilized to isolate pure compounds. This study validates and documents, in a systematic way, the antimicrobial properties of the R.natalensis used for many years by many people of the world. It also provides valuable
information for further phytochemical isolation and characterization studies of active
compounds, necessary for the development of new drugs. The extractions were carried out using broad spectrum of solvents (hexane, dichloromethane, ethyl acetate, and methanol).Fractionation was done using standard chromatographic techniques. A total of seven (7)compounds were isolated from R. natalensis. Three of the isolates were characterized and their structures were unambiguously established by detailed spectroscopic analysis that involved high resolution mass spectrometry, 1D and 2D-NMR spectral data experiments 1H, 13C, DEPT,COSY, HMBC, and NOESY. These compounds are: 3-(1-(2,4-dihydroxyphenyl)-3,3-bis(4-
hydroxyphenyl)-1-oxopropan-2-yl)-7-methoxy-4H-chromone-4-one (39), Rhuschromone, a novel compound isolated for the first time, 2’,4’ dihydroxychalcone-(4-O-5’’’)-4’’,2’’’,4’’’-trihydroxychalcone (40) and 3-((Z)-heptadec-13-enyl) benzene-1,2-diol (41), an urushiol.Compound 39 recorded the highest activity zone of inhibition (21mm) against S. aureas, which was found to be 50% as active the chloramphenicol standard used. The traditional use of the extracts in infections and inflammatory conditions is rationalized based on the content of the isolated compounds, and it has been proposed that the total crude extract, with its contents of so many bioactive compounds, could be formulated for use in many infections, microbial or fungal.Furthermore, not all of the species studied to date have been fully characterized for potential bioactivities. Thus, there remains a significant research gap spanning the range from lead chemical discovery through process development and optimization in order to better understand the full bioactive potential of many of these plants
Phytochemical and antimicrobial studies on Rhus natalensis
No full textMagister Scientiae - MScExtracts from the root bark, stem bark, and leaves of R. natalensis were screened for antibacterial activity against standard bacterial strains; Staphylococcus aureas, Escherichia coli and Pseudomonas aureginosa, and fungi; Candida albicans, Trichophyton mentagrophytes or Microsporum gyseum. Chromatographic techniques were utilized to isolate pure compounds. This study validates and documents, in a systematic way, the antimicrobial properties of the R. natalensis used for many years by many people of the world. It also provides valuable information for further phytochemical isolation and characterization studies of active compounds, necessary for the development of new drugs. The extractions were carried out using broad spectrum of solvents (hexane, dichloromethane, ethyl acetate, and methanol). Fractionation was done using standard chromatographic techniques. A total of seven (7) compounds were isolated from R. natalensis. Three of the isolates were characterized and their structures were unambiguously established by detailed spectroscopic analysis that involved high resolution mass spectrometry, 1D and 2D-NMR spectral data experiments 1H, 13C, DEPT, COSY, HMBC, and NOESY. These compounds are: 3-(1-(2,4-dihydroxyphenyl)-3,3-bis(4- hydroxyphenyl)-1-oxopropan-2-yl)-7-methoxy- 4H-chromone-4-one (39), Rhuschromone, a novel compound isolated for the first time, 2’,4’-dihydroxychalcone-(4-O-5’’’)-4’’,2’’’,4’’’- trihydroxychalcone (40) and 3-((Z)-heptadec-13-enyl) benzene- 1,2-diol (41), an urushiol. Compound 39 recorded the highest activity zone of inhibition (21mm) against S. aureas, which was found to be 50% as active the chloramphenicol standard used. The traditional use of the extracts in infections and inflammatory conditions is rationalized based on the content of theisolated compounds, and it has been proposed that the total crude extract, with its contents of so many bioactive compounds, could be formulated for use in many infections, microbial or fungal. Furthermore, not all of the species studied to date have been fully characterized for potential bioactivities. Thus, there remains a significant research gap spanning the range from lead chemical discovery through process development and optimization in order to better understand the full bioactive potential of many of these plants.South Afric
Structural investigation of the natural products composition of selected South African seaweeds.
No full textPhilosophiae Doctor - PhDRecently, a great deal of interest has developed towards the isolation of bioactive compounds from marine sources due to their numerous health benefits. Furthermore, marine algae are valuable sources of structurally diverse metabolites with scientifically proven therapeutic claims. The cell walls are rich in sulfated polysaccharides such as fucoidans in brown algae,
carrageenans in red algae and ulvans in green algae. These sulfated polysaccharides exhibit many beneficial biological activities such as anticoagulant, antiviral, antioxidative, anticancer and immunomodulating activities. They have great potential for further development as products in
cosmeceutical, pharmaceutical and nutraceutical areas. Although the mechanism of action is still not clear, their biological activities could be mainly attributed to their major secondary metabolites namely; phlorotannins, terpenoids and fucoidans. There was use of comprehensive chromatographic separations and a full analysis of isolates using one or other of the spectroscopic techniques. Antioxidant and cytotoxicity tests were perfomed in details for Ecklonia maxima. Furthermore, structural and electronic features of the phlorotannins were compared in an attempt to provide an explanation for the differences in their radical scavenging properties. In this regard, two main radical scavenging mechanisms, hydrogen atom transfer (HAT) and electron transfer (ET), were assessed in order to determine the preferred mode of radical scavenging. Fully relaxed geometry optimizations of the neutral and the radical species were performed utilizing DFT/B3LYP and DFT/UB3LYP methods respectively. In further studies, the structural and functional properties of sulfated polysaccharides from the three brown and one red seaweeds were
investigated. This was through detailed analysis of chemical composition of crude and purified polysaccharides using PMP - derivatization of hydrolysed sugars, anion exchange, molecular weight determination, ion chromatography , FT-IR, NMR to methylation analysis. The work reports isolation and characterization of compounds from four algae: Ecklonia maxima, phlorotannin derivatives, namely phloroglucinol (22), eckol (23), 7-phloroeckol (24), 2-phloroeckol (25) and a sterol, 24-ethylidine cholesterol (26); Splachinidium rugosum, 24-ethylidine cholesterol (
26), 1, 3-Dicapryloyl-2-oleoylglycerol (27), E-3,7,11,15-tetramethylhexa dec-2-en-1-ol (phytol) (2
8); Macrocystis angustifolia, 24-ethylidine cholesterol (26); a red seaweed Aeodes orbitosa, and E
-3, 7, 11, 15-tetramethylhexad ec-2-en-1-ol (28) and 17-(5-Ethyl-6-methylheptan-2-yl)-10,13-dimethyl-2,3,4,7, 8,9,11,12,14,15,16,17-dodecahydro-1 H-cyclopenta[a]phenanthren-3-ol (β-sitosterol) (29). Experimental findings and theoretical predictions of phlorotannins indicated that the radical scavenging activities followed the order 22< 23 < 25 < 24. Theoretical studies further indicated the ET mechanism is more significant than the HAT mechanism due to the high BDE values. Their polysaccharide structures were tentatively shown to have a backbone of (1-3) and (1-4) linkages with sulfate groups at O-2 and O-2, 3 positions. The only red algae studied contained, 2-O-methyl-D-galactose with (1-3) and (1-4)-glycosidic linkages possessing sulfate groups at positions 2 and 6
Structural investigation of the natural products composition of selected South African seaweeds.
No full textPhilosophiae Doctor - PhDRecently, a great deal of interest has developed towards the isolation of bioactive compounds from marine sources due to their numerous health benefits. Furthermore, marine algae are valuable sources of structurally diverse metabolites with scientifically proven therapeutic claims. The cell walls are rich in sulfated polysaccharides such as fucoidans in brown algae,
carrageenans in red algae and ulvans in green algae. These sulfated polysaccharides exhibit many beneficial biological activities such as anticoagulant, antiviral, antioxidative, anticancer and immunomodulating activities. They have great potential for further development as products in
cosmeceutical, pharmaceutical and nutraceutical areas. Although the mechanism of action is still not clear, their biological activities could be mainly attributed to their major secondary metabolites namely; phlorotannins, terpenoids and fucoidans. There was use of comprehensive chromatographic separations and a full analysis of isolates using one or other of the spectroscopic techniques. Antioxidant and cytotoxicity tests were perfomed in details for Ecklonia maxima. Furthermore, structural and electronic features of the phlorotannins were compared in an attempt to provide an explanation for the differences in their radical scavenging properties. In this regard, two main radical scavenging mechanisms, hydrogen atom transfer (HAT) and electron transfer (ET), were assessed in order to determine the preferred mode of radical scavenging. Fully relaxed geometry optimizations of the neutral and the radical species were performed utilizing DFT/B3LYP and DFT/UB3LYP methods respectively. In further studies, the structural and functional properties of sulfated polysaccharides from the three brown and one red seaweeds were
investigated. This was through detailed analysis of chemical composition of crude and purified polysaccharides using PMP - derivatization of hydrolysed sugars, anion exchange, molecular weight determination, ion chromatography , FT-IR, NMR to methylation analysis. The work reports isolation and characterization of compounds from four algae: Ecklonia maxima, phlorotannin derivatives, namely phloroglucinol (22), eckol (23), 7-phloroeckol (24), 2-phloroeckol (25) and a sterol, 24-ethylidine cholesterol (26); Splachinidium rugosum, 24-ethylidine cholesterol (
26), 1, 3-Dicapryloyl-2-oleoylglycerol (27), E-3,7,11,15-tetramethylhexa dec-2-en-1-ol (phytol) (2
8); Macrocystis angustifolia, 24-ethylidine cholesterol (26); a red seaweed Aeodes orbitosa, and E
-3, 7, 11, 15-tetramethylhexad ec-2-en-1-ol (28) and 17-(5-Ethyl-6-methylheptan-2-yl)-10,13-dimethyl-2,3,4,7, 8,9,11,12,14,15,16,17-dodecahydro-1 H-cyclopenta[a]phenanthren-3-ol (β-sitosterol) (29). Experimental findings and theoretical predictions of phlorotannins indicated that the radical scavenging activities followed the order 22< 23 < 25 < 24. Theoretical studies further indicated the ET mechanism is more significant than the HAT mechanism due to the high BDE values. Their polysaccharide structures were tentatively shown to have a backbone of (1-3) and (1-4) linkages with sulfate groups at O-2 and O-2, 3 positions. The only red algae studied contained, 2-O-methyl-D-galactose with (1-3) and (1-4)-glycosidic linkages possessing sulfate groups at positions 2 and 6
Never be silent : publishing & imperialism in Kenya, 1884-1963
No full textSocial communications are central to any social struggle. There is a sizable body of literature from other countries on the use of oral medium, newspapers, books and other forms of communications being used as tools for organising against a powerful enemy, as a training ground for cadres and for clarifying and developing revolutionary theory, ideology, organisation and practice. All this ensures a greater unity among those resisting oppression and exploitation. Thus revolutionary and liberation forces of Bolsheviks in the Soviet Union, the Communist Party of China, and in Vietnam had developed theories and practices of revolutionary publishing as part of their revolutionary work. This has also been the case during anti-colonial and anti-imperialist struggles in Africa, but very little of this has been systematically documented as an aspect of revolutionary communications policy and practice. While the
colonial communications systems have been reasonably well documented, the resistance communication systems remain largely undocumented and ignored. This book is an initial attempt to document this dynamic communications process in Kenya with its external struggles against colonialism and its complex internal struggles with overlaying divisions of race and class, Kenyan and foreign peoples. The main theme emerging from this experience is that people struggling to change their society always find ways of establishing their own system of communicating with the people they lead
and by whom they are led. Their mission of revolution, of change, of peace, of social and economic justice requires that they should never be silent. This was well understood and practised by the liberation forces in Kenya. They
were never silent
Development expenditures and the local financing constraint
No full textFocusing on the local financing constraint sheds new light on issues of aid, fiscal reform, and the management of public spending. The fungibility of aid need not translate into resource flows to fill the local financing gap. Indeed, project aid can widen the local financing gap. To augment direct local financing of development, aid must be nonproject aid that can generate local currency. In the longer term, project aid's effect on local financing lies in its impact on growth and on expanding the base for tax revenues, seigniorage, and borrowing. When inadequate local financing limits project implementation and effective use of aid, local currency funds are more valuable than project aid, at the margin--and it becomes important to reallocate local funds, to leverage project aid, and to raise the quality of investment projects. A persistent gap in local financing complicates programs of fiscal reform. For such programs to be effective, the local financing gap has to be confronted directly by matching planned local fund expenditures against expected local fund receipts. This requires a transparent database to develop indicators and to monitor the allocation and use of local resources.Development Economics&Aid Effectiveness,Economic Theory&Research,Environmental Economics&Policies,Payment Systems&Infrastructure,Fiscal&Monetary Policy,Environmental Economics&Policies,Development Economics&Aid Effectiveness,National Governance,Fiscal&Monetary Policy,Economic Theory&Research
A New Form of Authoritarianism? Rethinking Military Politics in Post-1999 Nigeria
No full textDespite the vast research that has been done on the Nigerian military, virtually all of these studies have failed to critically examine the accepted role of the military in the democratising phase. This is important because the relationship between the political elite and the military in post-military authoritarian states guarantees either democratic consolidation, or its reversal. In Nigeria, despite an appearance of significant progress in subordinating the military institution to democratic civilian authority, the military remains a crucial political actor in the polity. It appears that the military has yet to accept the core democratic principles of civilian oversight of the institution. This thesis, therefore, explores whether a new form of military authoritarianism is emerging in Nigeria, with the aim of understanding Nigeria’s military behaviour in a transitional phase, from prolonged military authoritarianism to democratisation. To examine this military behaviour, Alfred Stepan’s concept of military prerogatives that was used to understand the military’s behaviour in a transitional phase in Latin America is applied to Nigeria.
A crucial understanding of authoritarianism in Nigeria is initially discussed in this study using mainly document analysis strategy to examine whether multi-ethnic states, such as Nigeria, tend to have authoritarian systems. Six hypotheses form the core analysis of this thesis: first, that the military has retained significant military prerogatives; second, that retired military officers are gaining influential political and economic positions; third, autonomous military involvement in human rights abuses since 1999; and fourth, that civilian government oversight remains weak, and facilitates military authoritarianism. These hypotheses are primarily analysed using the elite interview technique. During the first half of 2011, the author conducted field research where serving and retired military officers were interviewed. The fifth hypothesis is that the military has intervened in politics post-1999. The examination of this hypothesis relies primarily on key security-related media reports (mostly newspaper editorials) on the military after 1999. The examination of the final hypothesis, that increases in military expenditures might facilitate a new form of military authoritarianism, relies primarily on descriptive statistical analysis. In addition, this study collated relevant historical materials that relate to the military, utilising national archival collections.
The empirical findings of this research did not identify a new form of military authoritarianism in Nigeria. The study, however, argues that the unrestricted institutional framework accorded the military has contributed significantly to authoritarian practices in the post-military era in Nigeria. This study discovered that there were similarities between the Brazilian and Nigerian militaries in regard to their military spending during their period in power. Both countries had lower defence budgets. Just as in Brazil, it appears that part of the reason the Nigerian military decided to relinquish power in 1999 had to do with its desire to gain a higher budget, something that was precluded in a military government struggling to retain a sense of legitimacy. The military needed a higher budget to modernise and re-professionalise its institution after more than a decade in power. This feature, which the Nigerian military shares with the Brazilian military, appears to justify the application to Nigeria of Alfred Stepan’s concept of military prerogatives.
Author Correction: Burdens of type 2 diabetes and cardiovascular disease attributable to sugar-sweetened beverages in 184 countries (Nature Medicine, (2025), 10.1038/s41591-024-03345-4)
No full textCorrection to: Nature Medicinehttps://doi.org/10.1038/s41591-024-03345-4, published online 6 January 2025. In the version of the article initially published, in the eighth paragraph of the Discussion, the text “Among large nations, the largest increases in SSB-related T2D burdens were in Mexico, Thailand and the United Kingdom, and in CVD burdens, Colombia, Nigeria, Thailand and Russia. These changes align with rises in SSB consumption in these nations12. Similarly, declining SSB-related cardiometabolic burdens in Brazil, the United States and the United Kingdom (for CVD) are consistent with their decreasing SSB consumption from 1990 to 202012” was incorrect and has now been updated to “Among largely populated nations, the largest increases in SSB-related T2D incidence was in Colombia, USA and Argentina; and in CVD incidence, Nigeria, Russia, Colombia and Thailand. These changes generally align with rises in SSB consumption in these nations, except in the US where slight declines in SSB consumption were offset by increased burdens of diabetes 12. Similarly, declining SSB-related cardiometabolic burdens in Turkey, Brazil, and the United States and the United Kingdom for CVD are consistent with their decreasing SSB consumption from 1990 to 202012.” Additionally, Supplementary Data 1 and 2 have been updated to remove decimals in values greater than 100. These corrections have been made to the HTML and PDF versions of the article. © The Author(s) 2025
Endemic diseases and agricultural productivity: Challenges and policy response
No full textContrary to Asian countries, the agricultural sector in Africa had not benefited from the green revolution success. After a long time of disinterest in the agriculture sector in Africa, several voices arise now in favour of greater efforts towards this sector. Several studies tend to show the crucial role of agriculture in African countries’ growth and highlight the huge need of increasing the productivity in this sector. If increase in agriculture productivity requires both an expansion of irrigated areas and the adoption of high yield varieties, those innovations and their high development could be the source of negative health (and environmental) effects. Using a mega-analysis, this paper highlights first the links between health, disease and development and then agricultural productivity. The literature review shows that the negative effect of bad health was not systematically checked, and that the intensity of this effect depends of the disease, but also of the work productivity and the existence or not of a coping process. The second part of the paper focused on the development of high intensive agriculture as a risk factor for farmers’ and rural inhabitants’ health. This survey shows that whether irrigation and fertilizer and pest intensive use could be considered as highly health (and environmental) risk factors, appropriate control measures (such as for examples systematic maintenance of irrigation canals, alternate wetting and drying of irrigated fields or integrated pest management) considerably reduce this risk, while at the same time, increase the agriculture productivity.agriculture, productivity, endemic disease, health risk factor, Africa
