PHD-Department of Chemistry

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    Phytochemical and molluscicidal studies on Kenyan solanum species
    (Kenyatta University, 2000-06) Wafula, Alphonse Wanyonyi
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    Computational chemistry studies of (1,7) sigmatropics hydrogen shiftd in Z,Z-1,3,5- heptatrien systems and esterification reactions
    (2011-07-19) Macharia, Godfrey Kibe; Rajab, M.S.; Muthakia, G.K.
    Density functional theory has been used to study mechanisms of the reactions involving [1,7]-sigmatropic hydrogen shift in Z,Z-1,3,5-heptatriene systems, esterification of acetyl chloride with methanol and acid-catalyzed esterification of carboxylic acids with methanol. The calculations employed the B3LYP functional, with 6-31+G(d) basis sets. Mechanism routes were computed, with complete optimization of all intermediates and transition states. The effect of electron-donating and electron-withdrawing substituents in Z,Z-1,3,5heptatriene systems was investigated. Analysis of the geometries, energies and electronic characteristics of the sigmatropic transposition compared to those of the unsubstituted cases provided insights into substituent effects of the reactions. The study revealed that the inductive and mesomeric effects of heteroatoms or heterosubstituents are of great importance in the energetics of the transformation. Steric effects also play an important role due to the geometrical constraints of the reaction.Generally increasing the electron density of the system, decreases the electron density on the protropic proton resulting in the decrease of the activation energy. For the esterification of acetyl halides with methanol, the calculations suggest that the reaction proceeds through a loose transition state with a concerted SN2 mechanism. The nucleophilic methanol attacks the carbonyl carbon at Biirgi-Dunitz trajectory and the interaction is subject to general base catalysis, either by a second molecule of methanol or a solvent molecule. This explains the mixed reaction kinetics observed from experimental data. The calculations suggest that the acid-catalyzed esterification of carboxylic acids with methanol involve interaction of both the proton and the counter ion. The calculated activation parameters in the solvent model are in excellent agreement with experimental results. The computational results for the methanolysis of acetyl chloride and acid-catalyzed esterification reactions call for a re-evaluation of some commonly accepted classical mechanistic pathways. For the reactions investigated in this study, the calculations revealed a new mechanistic insight of the reaction pathway
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    Effects of selected media on novel portland pozzolana cement
    (2011-07-19) Muthengia, J. W.; Gerald Muthakia; Karanja Thiong'o
    Cement is subject to degradation by aggressive media found in the environment. Durability tests are therefore necessary for any cementitious material in a given environment. The work reported in this thesis involved the study of the effects of selected aggressive media on a cement, made from inter-mixing Ordinary Portland Cement (OPC), dried acetylene lime sludge (DALS) and an incinerated mix of reject bricks (BB), spent bleaching earth (SBE) and rice husks. The cement was labelled Portland Combined DALS Cement (PCDC). Initial tests showed that PCDC met the Kenya Standard requirements for Portland Pozzolana cement (PPC). PCDC was subjected to various media which included sea water, distilled water, chloride and sulphate solutions in a laboratory set-up. The experiments were carried alongside OPC, 25 % Pulverised Fuel Ash substituted OPC (OPC + PFA) and commercial PPC. The study was carried out in two phases; cement mortar moulded into 100 mm cubes subjected to the media and reinforced mortar cubes subjected to a wet and dry alternate environment of 3.5 % sodium chloride solution. PCDC exhibited continued compressive strength gain in all media except in chloride solutions. PCDC exhibited comparable gain in compressive strength and selected ions intake/leach to PPC in sulphate solutions and distilled water. PCDC exhibited higher strength gain than OPC in distilled water. Except in chloride solutions, PPC exhibited higher strength gain than OPC. In Corrosion tests, the PCDC mortar rebars showed early attainment of active corrosion coupled with higher corrosion rates over a short period of time than OPC as w/c ratio was increased. The PCDC showed a decreased chloride penetration than OPC as w/c and depth of cover increased. PCDC showed the lowest apparent chloride diffusion coefficients. The resistivity of PCDC in the aggressive media suggested that it required greater depths of cover, where reinforcement was to be used, and long term curing to improve on its resistivity. The tests showed that PCDC can be used for general construction work in the tested media in a similar manner to PPC
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    Characterisation of Kenyan honey and a design model for processing equipment
    (2011-07-26) Bichang'a, R.M. Robert
    Honey production potential in Kenya is estimated to be 100,000 metric tonnes which can earn the country between Ksh 15-20 billion in foreign exchange. This production potential is not met because of poor apiculture practices. Lack of appropriate honey extraction and processing equipment which is affordable and accessible has resulted into production of low level and poor quality honey. Honey produced in Kenya is from different regions and botanical sources and have different physicochemical and biochemical properties. There has been no study on these important properties in order to characterise and regulate the honey quality. The purpose of this study was to investigate the physicochemical and biochemical properties of Kenyan honey from different regions and design a model to fabricate and construct a processing equipment to improve the quality of local honey. Honey from the four regions of Kenya; Rift Valley, Central, Eastern and Coast was analysed for moisture content, electrical conductivity, ash content, mineral content, pH, HMF, water insoluble. The mean moisture content for the four regions was 19.48 ± 0.11% varying from 1 x.44-29.60%. Coast region had the highest mean moisture content (20.77 ± 0.46%) while Rift Valley had the minimum (18.84 ± 0.10%). The mean electrical conductivity for the four regions was 0.549 ± 0.029 mS ranging from 0.020-2.25 mS. Rift Valley honey had the lowest mean value (0.059 ± 0.015 mS) while Eastern had the highest. The mean viscosity for the four regions at 30 *c was 4342.98 ± 314.08 centipoises, varying from 1000-7700 centipoises. Rift Valley had the most viscous honey with a mean of 5607.75 ± 393 centipoises whereas central had the least viscous with mean of 3335.00 ± 152.53 centipoises. The mean apparent reducing sugars for the four regions before and after hydrolysis were 69.41 ± 0.17 and 71.39 ± 0.17% respectively, ranging from 54.43-78.27% in the same order. Fructose was the dominant specific sugar in honey for the four regions followed by glucose, sucrose and maltose. The mean values of pH, HMF, density, diastase enzyme activity, and hygroscopicity for the four regions were 4.32 ± 0.02, 17.54 ± 1.46 mg/kg, 1.41 ± 0.00 g/cm3, 15.04 ± 0.460 DN, and 8.67 ± 0.01% respectively. In the design of extractor warmer equipment, the overall mean of density and viscosity were used to determine the dimensions and heat transmission of the vessels. The pH was used for the selection of material for construction. Moisture content, HMF, hygroscopicity and diastase were used to set the processing and storage conditions. Kenyan honey was identified as floral (blossom), honeydew honey, compound or mixed honey with Newtonian behaviour. No thixotropic honey was found in these regions. The moisture content of Kenyan honey was found to be below the maximum permitted limit of (21%) and therefore stands no risk of fermenting. Most of the Kenyan honey had matured with acceptable levels of proline and diastase number. The physicochemical parameters of Kenyan honey were successfully used to design honey extraction and processing equipment which can be used to process honey in any part of the country.
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    Phytochemical and pharmacological investigation of four Tanzanian medicinal plants for anti-protozoal activity
    (2011-08-03) Malebo, Masanja Hamisi
    Protozoal diseases like malaria, trypanosomiasis and leishmaniasis, caused by Plasmodium, Trypanosoma and Leishmania, respectively, have overwhelming impact on public health in developing regions. Due to their prevalence, virulence and drug resistance, they are the most serious and widespread parasitic diseases encountered by mankind The inadequate armory of drugs, high cost and lack of new drugs are the major limiting factors in the fight against the three diseases. Consequently, there is continuing need of research on the discovery and development of new effective and safe anti-protozoal drugs. In this work, solvent extracts from four Tanzanian medicinal plants: Annickia kummeriae, Pselalospondias microcarpa, Drypetes natalensis and Acridocarpus chloropterus, were tested for anti-protozoal activity. Anti-protozoal bioassays revealed 14 solvent extracts with strong i ) moderate in vitro antiplasmodial activity (IC5o 0.12_+0.01-5.50_+0.27 gg/ml), 6 with moderate anti-trypanosomal activity (IC5o 2.3±0.43-5.40_+0.64 pg/ml) and only 3 with mild inti-leishmanial activity (IC5o 9.25+0.54-9.79+2.5 gg/ml). Annickia kummeriae, P. micro arpa and D. natalensis solvent extracts exhibited good anti-plasmodial activity and favourable selectivity (SI 29.22,250). The strong anti -plasmodial, moderate anti-trypanosomal aid mild anti -lei shmanial activity of the methanolic extract of A. kummeriae leaves encoura~ ed the isolation of antiprotozoal compounds. Bioassay-guided chromatographic fraction ion led to isolation and identification of fractions with stronger anti-plasmodial activi and more favourable selectivity than the solvent extracts. Seven anti-protozoal al Voids: palmatine (82), jatrorrhizine (83), lysicamine (127), trivalvone (128), annickine ( 129), columbamine (130) and (-)-tetrahydropalmatine (131), were identified by spectroscopic methods and subjected to in vitro anti-protozoal assays. The isolated alkaloids showed good selectivity and strong to moderate anti-plasmodial activity (IC5o 0.08_+0.001-2.3+0.44 [t-'ml), mild to weak antitrypanosomal (IC5o 3.2++0.01-14.30_+0.1 pg/ml) and anti-leishmaniA activity (IC5o 2.7++0.120.4+_0.1 gg/ml). Chromatography of A. chloropterus extracted to the isolation and identification of 5 triterpenes: (3-sitosterol (132), stigmasterol (133), friedelin (134), oleanolic acid (124), ursolic acid (123); and 5 flavonoids: apigenin (135), luteolin (136), vitexin (137), kaempferol (138) and quercetin (139). Quercetin (139) exhibited moderate in vitro anti-plasmodial activity (IC5o 2.6++0.05 pg/ml) while the rest of compounds were inactive. Mild to weak in vitro anti -trypanosomal activity was observed in quercetin (139) (IC5o 3.60±0.1 Frg/ml), ursolic acid (123) (IC5o 7.80±0.1 pg/ml) and apigenin (135) (IC5o 9.0+0.1ug/ml). Good in vitro anti-leishmanial activity (IC50 0.80_+0.001, 2.10_+0.1, 2.20+0.1, 5.90_+ 0.1 and 3.5+0.2 ug/ml) and favourable selectivity were observed with ursolic acid (123), quercetin (139), kaempferol (138), apigenin (135) and oleanolic acid (124), respectively. Chemical structure-biological activity relationship comparisons confirmed that, the methoxyl groups at C-2, C-3 (ring A) and C-9, C-10 (ring D) together with the quaternary nitrogen atom in position 7 are the structural moieties required for strong anti-plasmodial activity in protoberberine alkaloids. Structure-activity-relationship (SAR) comparisons in the isolated triterpenoids confirmed that, the hydroxyl group at C-3 with methyl groups at C-23, C-25, C-26 and C-30, C-12/C-13 double h:md, the carboxylic acid group at C-28, and hydrogen at C-20 in the molecular framework )f ursolic acid (123) are the structural moeties responsible for the strong anti-leishmania! activity whereas in the isolated flavonoids, the hydroxyl groups at C-3 and C-3' in the apigenin (135) molecular framework are the structural moeties responsible for the strong anti-protozoal activity observed. The alkaloids with strong anti-plasmodial and me gate anti-trypanosomal activity may provide lead compounds for the development o drugs for malaria and trypanosomiasis. Similarly, the strong to moderate anti-leishmani I activity of the isolated triterpenes and flavonoids render them good candidates as molecular templates for new drug development.
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    Isolation and characterization of antimalarial compounds from selected medicinal plants used in Coastal Kenya
    (2011-08-12) Ng'ang'a, M. M.
    Malaria remains a devastating scourge on the lives and livelihoods to the millions of global citizens living in the tropics. Plant-derived antimalarials have made and continue to make an immense contribution to malaria chemotherapy and novel drug entities continue to be developed through research into their constituents. The long established use of quinine and the more recent introduction of artemisinin and its derivatives as highly effective antimalarials also demonstrate that plant species are an important resource for the discovery of new antimalarial agents. In search for new antimalarial principles, three plants namely Drypetes gerrardii, Euclea divinorum and Ozoroa insignis normally used to treat malaria and other ailments among `Chonyi' people in Kilifi District, Coast province were investigated. The crude extracts were screened against chloroquine (CQ susceptible and resistant strains of Plasmodium falciparum (D6 and W2, respectively). Isolation and purification of bioactive principles present in the active extracts was done using chromatographic techniques (CC, TLC, Prep TLC). The in vitro cytotoxicity assay was carried out using VERO 199 kidney epithelial monkey cells. The structures were established conclusively by using UV, IR, MS and extensive 'H and 13C NMR spectra analysis and comparison with data from the cited literature. The CH2C12 and EtOAc crude extracts obtained from the leaves of Drypetes gerrardu and Euclea divinorum as well as root bark of Ozoroa insignis showed high in vitro antiplasmodial activity in the range of ICso = 6.12 ± 0.45 - 17.29 ± 1.44 pg/ml and 8.42 ± 1.06 - 12.09 ± 0.67 gg/ml against CQ-susceptible strain, respectively. Phytochemical investigations of the petroleum ether and dichloromethane mixture and the ethyl acetate crude extracts of Drypetes gerrardii leaves afforded four friedelane-type triterpenoids (DGL 1 - DGL 4), one hopane-type triterpenoids (DGL 5), one lupane-type triterpenoids ((DGL 6), one steroid (DGL 7) and a biflavonoid (DGL 8) for the first time. The compounds exhibited no antiplasmodial activity (ICso > 10 pg/ml and weak cytotoxicity (ICso >20 pg/ml). Chemical analyses of the leaves of Euclea divinorum yielded three new naphthalene derivatives namely eucleanal A (EDD 5), eucleanal B (EDD 6), eucleanal C (EDD 7) among four napthoquinones (EDD 1 - EDD 4), three lupane-type triterpenoids (EDD 8, EDD 9 and EDD 11), one ursane-type triterpenoid (EDD 10) and a sterol (EDD 12a and 12b). The 2-methylnapthazarin (EDD2) exhibited high antiplasmodial activity against CQ-resistant strain with an ICso value of 0.50 ± 0.16 pg/ml but also displayed the highest cytotoxicity with an ICso value of 0.94 pg/ml and a selective index (SI) of 1.90. Similarly, phytochemical screening of the CH2C12 and Et0Ac of the root bark of Ozoroa insignis yielded one oleanane-type triterpenoid (OZD 1), three lupane-type triterpenoids (OZD 2 - OZD 4), three anarcardic acid derivatives (OZD 5-6) and a flavone (OZD 7) for the first time. 3BHydroxylup-12:20(29)-diene (magnificol) (OZD 3) exhibited high antiplasmodial activity (ICso = 1.81±1.03 pg/ml) against CQ-resistant strain and weak cytotoxicity (ICso > 20 gg/ml) with an SI > 11.05 pg/ml indicating its selectivity for the malaria parasite. The antimalarial activity reported herein explains and verifies the therapeutic efficacy claimed for these plants in traditional medicine. In addition, the isolated compounds with appreciable activity may be chemically modified to generate leads with enhanced antiplasmodial activity, reduced cytotoxicity and improved bioavailability
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    ADH/ADLH polymorphism as biochemical and genetic markers in study of alcohol tolerance in selected Kenyan populations
    (2011-08-16) Korir, Elena Doudoladova
    Excessive alcohol consumption is a major health hazard worldwide. Alcohol is commonly used and often abused in Kenya, especially by the youth. For European, Asian, Australian and American populations, studies have shown linkage between polymorphisms of the alcohol dehydroggenase (ADH) and aldehyde dehydrogenase (ALDH), the ethanol metabolizing enzymes, with the increase of alcohol intake. For Africans, no studies on heterogeneity of ADH and ALDH and its relationship to alcoholism, alcohol intake and alcohol drinking behaviour have been reported. The aim of this study was to find out the distribution of alleles of ADH 2, ADH 3, and ALDH 2 loci in the selected Kenyan populations namely the Kolweny, Siaya, Longisa, Limuru and Rugunga and to investigate the association of these ADH/ALDH alleles with alcohol drinking and alcoholism. These five Kenyan populations represent two major African groups namely the Bantu and Nilotes. Different gender and age groups of the selected Kenyan communities were screened for ADH 2, ADH 3 and ALDH 2 polymorphisms via phenotyping of hair lysates using high resolution isoelectric focusing.. In addition, information on education, marital status, occupation, drinking behaviour, alcohol sensitivity, alcohol intake, age of regular alcohol drinking, alcohol drinking experience, alcohol dependence, emotional response to alcohol and preference of alcoholic drinks was collected via a questionnaire. The data obtained on ADH 2, ADH 3 and ALDH 2 polymorphism and alcohol drinking behaviour was statistically analyzed using chi-square, t-test and Fisher's exact test. Three hundred and seventy one adult volunteers participating in the project from all Kenyan study groups were divided into groups on the basis of alcohol tolerance. Alcohol-drinking parameters of alcohol use were analyzed with respect to alcohol tolerance. The significant difference in alcohol intake, alcohol drinking experience, alcohol sensitivity, emotional response to alcohol, the role of ADH 3*1 allele in the drinking behaviour and preference of alcoholic drinks were determined among individuals with high and low alcohol tolerance. ADH 2, ADH 3 and ALDH 2 polymorphism showed significant relation to alcohol intake (among alcoholics), alcohol drinking experience (among nonalcoholics), sensitivity to alcohol, alcohol drinking behaviour, mode of alcohol drinking, and preference of alcoholic drinks. ADH and ALDH heterogeneity was not associated with the difference in alcohol intake (among nonalcoholics), age of regular drinking and emotional response to alcohol. The role of different socio-demographic, biochemical and genetic factors in alcohol drinking and spread of alcoholism were identified for each Kenyan study group. The Kolweny, Siaya, Limuru and Rugunga populations have dominance of individuals with high alcohol tolerance and relatively low spread of alcoholism in the populations. The Longisa population had relatively high proportion of individuals with low alcohol tolerance and high occurrence of alcoholism in the community. The research findings may be used to formulate ethnically adequate methods of diagnosis, treatment, and management of alcoholism in relation to alcohol tolerance in the studied Kenyan populations
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    Effects of dehydration of dark-greenn, leafy vegetables on bioavailability and bioconversion of serum beta-carotene among preschool children
    (2011-10-25) Oyugi-Nawiri, Mildred Pauline
    Vitamin A, an essential micronutrient has its deficiency remaining as a major public health problem in developing countries. The deficiency is caused by insufficient intake of foods rich in vitamin A or pro-vitamin A carotenoids and its prevalence contributes substantially to morbidity and mortality among children. Carotenoids, with (b-carotene as the primary pro-vitamin A carotenoid in dark green leafy vegetables (DGLVs), are important for their various biological functions. The DGLVs are season dependent but can be preserved by dehydration to ensure their availability during the dry seasons to reduce cases of the deficiency. The R-carotene content and retinol (vitamin A) in serum of preschool children after consumption of dehydrated cowpeas and amaranthus leaves were quantified. Preschool children (study subjects) were involved in a 13-week intervention period. Extracts from vegetable and serum samples were analysed by High Performance Liquid Chromatography. Elution was performed isocratically with systems of methanol:dichloromethane:water (79:18:3, v:v:v), methanol:dichloromethane:water (83:15:2, v:v:v) and acetonitrile:water (85:15, v:v) for vegetable samples, serum (3carotene (S-BC) and serum retinol (S-R) analysis respectively. Fresh blanched vegetable leaves, contained high levels of the all-trans b-carotene; 779-827mg/g DM for cowpeas and 553-639mg/g DM for amaranthus. Although they reduced with dehydration and cooking, retentions for b-carotene were over 50% after dehydration and cooking. Thus, recipes provided sufficient amounts of retinol equivalents (RE)/day from both fresh and sun-dried vegetables to meet the recommended daily allowances for the study subjects. Serum beta-carotene concentrations were found to be within the normal range at baseline and increased significantly post-interventional for both study groups (p<0.000, df = 110, for fresh vegetable group and p<0.000, df = 38 for dehydrated vegetable group. There was a negative correlation between the baseline S-BC and change in S-BC for study subjects. However, the increase in S-BC of subjects in the fresh vegetable group was higher as compared to those of the sundried group. Although the control group for the fresh vegetable study group had an increase in S-BC, that of the dehydrated group had a decrease, but these changes were not statistically significant. The subjects in the fresh and dehydrated vegetable groups had marginally lower S-R concentrations at baseline but there was significant changes after intervention (p<0.000, df = 110, for fresh vegetable and p<0.000, df = 38 for dehydrated group). McNemars chi-square tests showed that at baseline, 55% and 70% of study subjects in the fresh and dehydrated vegetable study groups respectively had low S-R concentrations with the percentages reducing to 36% and 30% respectively post-intervention. Correlation analysis was negative between the baseline S-R and change in S-R for subjects in both the study and control groups. While data from individual subjects support the homeostatic regulation of vitamin A status, this study concludes that, intervention with the dehydrated vegetables improved the bio-availability of beta-carotene and bioconversion of beta-carotene to retinol. The findings contribute to the link between increased consumption of carotenoids from DGLVs and bio-availability of the same.
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    Isolation and structure elucidation of biologically active secondary metabolites from Kenyan fungi
    (2012-02-14) Omolo, Ouma Josiah
    Fungi, though the earliest source of secondary metabolites, remain an under-exploited for novel compounds especially when considering their diversity. Through screening many different fungi over the years, it is apparent there are variations in secondary metabolite production between different isolates of the same species from different substrates and in different habitats. Hence to target novel fungal secondary metabolites, a comprehensive screening programme has to be designed. A total of 130 strains of fungi were isolated from soil samples, fruiting bodies or decaying wood substrates collected from various places and some obtained from persons and institutions stocking such micro-organisms in Kenya. The strains were cultivated in submerged cultures in 500ml scale and extracts were prepared from both the mycelium and the culture filtrate at the end of fermentation. The extracts were screened for any significant activity in antifungal, antibacterial, nematicidal and phytotoxicity bio-assays. Where strong activity was observed, further screening was carried out to optimise production of the responsible active compounds. Four strains, namely Aspergillus viridi-nutans, Stereum sp. 99123, Tyromces albidus and a basidiomycete, stain 99126, showed consistent results and were further processed for biologically active except A.viridi -nutans and only stereum sp. 99123 had nematicidal principles. In all four cases the culture filtrate extract was responsible for the observed activities. These four were further cultivated on various scales ranging from 1-100 litres quantities and extracts were prepared from the filtrate either by direct solvent extraction or adsorption on a resin and subsequent elution. The solvents were removed under reduced pressure and the extract concentrated to dryness. Bio-assay guided fractionation of the extracts was done using chromatographic methods. Six compounds namely was abidienone B1, was bienone Bo, phomaligin A and variation as well as new analogues viriditin and 13- 0-methylviriditin were purified from A. viridi-nutans. Variation was responsible for the strong antifungal activity shown by extracts of A. viridi-nutans. Erinapyrone C, striatal D and six other new compounds were obtained from Stereum sp. 99123. Striatal D was found to be a strong antimicrobial and cytotoxic compound. Complicatic acid was purified from Tyromces albidus and a compound JO224K51 with interesting structural features from the basidiomycete, strain 99126. Both complicatic acid and JO224K51 had strong antibacterial activity. Structures of these compounds were elucidated using spectroscopic techniques. Ultraviolet, infrared, mass spectra and nuclear magnetic resonance measurements were taken as principal complementary techniques in discerning the structures. Proton and carbon-13 NMR spectra were recorded as well as 2D NMR experiments performed for each of the compounds to decipher the structure. Novelty of the compounds was established by comparing the observed properties with those of known compounds in instrument in -built electronic libraries, in the literature and various current natural products and chemical databases.
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    Isolation and structural elucidation of bioactive metabolites from Fungi, Trichoderma species and a higher plant, Tephrosia Aequilata
    (2012-02-14) Tarus, Paul K.
    The tea plant, Camellia sinensis (L.) O. Kuntze is an important crop in the agriculturally based economy of Kenya. It ranks second to tourism as an earner of foreign exchange and provides a livelihood for more than a million people. There are a number of diseases affecting the tea plant but the most prevalent is armillaria root rot caused by the fungus Armillaria mellea. Trichoderma species is an imperfecti fungi and is reported to be antagonistic against Amillaria mellea and Mycena citricolor fungus, the causative agents of armillaria root rot in tea and American leaf spot disease of coffee, respectively. The first part of the study discusses the effects of the crude extracts and isolated compounds from Trichoderma species on the test organisms; Paecilomyces variotii, Penicillium notatum, Nematospora corylii, Mucor miehei, Bacillus brevis, Bacillus subtilis, Enterobacter dissolvens, Sarcina lutea and Armillaria mellea. The crude culture broth extracts and pure compounds isolated from Trichoderma harzianum, T longibrachiatum and T koningii when cultured in media M1 to M6 were investigated individually for in-vitro antifungal and antibacterial activities by agar diffusion technique. Some of the culture broth extracts produced definite antifungal and antibacterial activities against most of the test organisms. The results indicate that some extracts were fungicidal and antibacterial at concentrations upto 100 ug per 6 mm disks. T koningii showed the least activity against most of the test organisms especially against the yeast, Nematospora corylii. The two compounds, 2-phenylethanol (1) and 2-(p-hydroxypheny) ethanol (tyrosol) (2) obtained from T harzianum were the most predominant metabolites and are being reported for the first time from Trichoderma species. The most active metabolite isolated from these strains was 6-n-pentyl-2H-pyran-2-one (3), which showed the highest antifungal and antibacterial activity and completely inhabited the growth of Armillaria mellea fungus when tested at a concentration of 200 ppm. Compound 4 (sorbicillin) and compound 5 ergosterol were isolated from the mycelium of T longibrachiatum. Compound 4 exhibited moderate activity against the fungal test organism. The second part of the study describes the extraction, isolation and structural elucidation of secondary metabolites from the roots of the plant, Tephrosia aequilata Baker. Tephrosia (Leguminosae) is a large tropical and subtropical genus estimated to contain about three hundred species. The petroleum ether extract of the roots of Tephrosia aequilata was subjected to chromatographic separations. This led to the isolation of five flavonoids, which included two --hydroxychalcones, two --oxygenated chalcones and a pterocarpan. All four chalcones were prenylated. The compounds demethypraecansone (30) and trans-praecansone A (33) are metabolites that are being reported for the first time from the plant, Tephrosia aequilata. The pterocarpan, 3, 4: 8, 9-dimethylenedioxypterocarpan (31), the --oxygenated chalcone, cispraecansone A (32) and --hydroxychalcone, cis-praecansone B (34) isolated in the present study are new natural metabolites. The pure compounds obtained from T aequilata were tested against gram-positive and gram-negative bacteria, fungus, yeast and Plasmodium falciparum. Demethylpraecansone B (30) exhibited moderate activity against gram-negative bacteria while cis-praecansone B (34) had moderate activity against gram-positive bacteria.
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    The role of serum zinc, copper, retinol and alpha-tocopherol in modulating immunity in HIV and AIDS subjects in Western Kenya
    (2012-03-27) Mbakaya, Charles; Nyambaka, H. N.; Judith Waudo
    From the early 1980s, scientists continue to debate on HIV as the cause of AIDS with few arguing that AIDS is caused by chemicals, drugs and malnutrition. A nutrition intervention study in Kenya using VIUSID™, a recommended daily allowance compliant formulation with respect to ascorbic acid, pyridoxal, folic acid and zinc sulphate, was ineffective in restoring serum zinc levels and immunity of HIV and AIDS subjects in 12 weeks. The purpose of this study was to determine serum micro-nutrient levels, assess blood for immune markers and establish safety of an intervention with VIUSID TM administered together with mega doses of zinc, selenium and vitamins A, B12, C and E in HIV and AIDS subjects. Ninety subjects were sequentially recruited from VCT centres in western Kenya and clinically examined at baseline and at the 12th week. For intervention, subjects were administered with VIUSID TM together with citric acid (Arm 1) and VIUSID™ together with citric acid and with mega doses of zinc, selenium and vitamins A, B12, C and E (Arm 2) for 8 weeks. In both Arms however, administration of VIUSID ™ alone was continued to the 12th week.Venous blood was obtained for determination of micro-nutrient status, viral load, liver function and immune testing. Serum micro-nutrient levels were determined at monthly intervals, serum zinc and copper being determined using a Flame Atomic Absorption Spectrophotometer (F AAS) while retinol and alpha-tocopherol levels were by a High Performance Liquid Chromatograph (HPLC) as respective test kits were used for immunological, virological and liver function tests. Data entry and analysis was by SPSSIPC+ version 11.5, analysis being mainly by parametric and non-parametric methods between and within Arms 1 and 2. Spearman's Rho correlations were used to establish linkages between measured variables at 'baseline, during and after intervention. The ninety (90) subjects recruited and randomized into the study were aged 39.0±8.9 years, 70% were female, 47.1% were widows, 22.2% had a history of TB while 54.4 % ate 3 meals a day and 12.2% were confirmed HIV-seronegative despite losing spouses to HIV and AIDS. There were clinical improvements in 74 subjects who completed the study a significant increases in serum zinc levels occurred in both arms by the 4th week, more so in subjects on mega-doses. These declined to near baseline levels at the 12th week, probably suggesting a physiological regulation of the way nutrients were utilized. Although subjects in Arm 2 had significant increase in CD4 cell count (p = 0.007) and near significant viral load reduction (p = 0.104), those in Arm 1 had insignificant increase in CD4 cell count (p = 0.722) but significant decrease in viral load (p = 0.030). Low serum zinc correlated with HIVseropositivity (p = 0.0001) and high optical desnsity of HIV antibodies (p = 0.002). High serum retinol level at baseline was associated with better management outcomes by the Ith week of supplementation as use of mega-dose supplements had both clinical and immunological benefits and near-significant reduction in viral load. Low doses of micro-nutrients favored viral load reduction, this being in agreement with other studies. Liver function tests of the subjects stayed normal in both study Arms, suggesting the interventions were safe for use. Therefore. use of VIUSID™ with mega-dose micro-nutrients was safe and more effective than VIUSIDrrv1 only in management of HIV and AIDS subjects. From this study, nutrition has a role in management of HIV and AIDS and probably supports the view that malnutrition is a key factor in HIV and AIDS. Further work should be undertaken to develop and up-scale this intervention with a view to mainstreaming its use in healthcare delivery in Kenya and beyond, especially considering that HIV and AIDS drugs present several challenges, including adverse health effects, resistance and compliance.
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    Susceptibility of tsetse (Glossina species) to trypanosome infection in relation to midgut trypsin, trypsin-like enzymes and other molecules
    (2012-04-17) Kongoro, Jedida A.
    Post-feeding midgut trypsin levels and abilities of midgut homogenates to transform parasites were compared in Glossina morsitans morsitans, G. longipennis and G. fuscipes fuscipes. Peak midgut enzyme levels in the different species occurred between 48 and 72 h post-feeding. Glossina m. morsitans had the lowest peak in enzyme activity whereas G. f. fuscipes the highest. These differences were highly significant (P < 0.05, F = 0.02, n = 28). Midgut enzyme levels in the three Glossina species were, however, similar upto 24 h post-feeding (P > 0.05). The abilities of midgut homogenates of G. m. morsitans, G. longipennis and G. f. fuscipes to agglutinate Trypanosoma brucei brucei, were investigated. Glossina f. fuscipes and G. longipennis midguts had twice as much lectin as G. m. morsitans, basedon their ability to agglutinate T. brucei. However, there was no significant difference in the levels of enzyme inhibition in the midguts of these Glossina species by T. b. brucei and T. congolense. Rates of infection with T. b. brucei and T. congolense in the different Glossina species were studied. Mature T. b. brucei infection rates in G. longipennis were less (P < 0.05, F = 0.38, n = 12) than those infection rates were higher in G. m. morsitans (P < 0.05, F = 0.28, n = 16) than those in G. longipennis and G. f. fuscipes. There were no significant differences between the species with regards to midgut infections with either T. b. brucei or T. congolense. The effect of age of flies on their susceptibility to trypanosome infection was studied in G. m. morsitans, G. longipennis and G. f. fuscipes. There were no differences between the teneral and non-teneral flies in the ability of their midguts to transform T. b. brucei and T. congolense (P > 0.05). However, the midguts of non-teneral flies showed greater lysis of T. b. brucei than their respective tenerals. Glossina f. fuscipes midgut contents had the greatest lytic effects on T. congolense among the non-teneral flies. In addition, there were no significant differences with respect to rates of infection in either teneral or non-teneral flies. The midgut trypsin profiles in teneral and non-teneral starved (120 h) flies did not differ within species. Two different G. pallidipes populations were assessed for midgut trypsin levels and their ability to transform parasites. There were no statistical differences, in enzyme profiles and trypanosome transformation rates, between Lambwe Valley and Nguruman populations of G. pallidipes.i My study has shown that higher post-bloodmeal trypsin and lectin activities exist in the midguts of G. longipennis and G. f. fuscipes compared to those of G. m. morsitans. This gives a concomittantly greater lysis and agglutination titres in the two species, affording them lower susceptibility to trypanosome infection than in G. m. morsitans. Similarities in trypanosome transformation and midgut infection rates in the different Glossina species may be attributed to similarities in their trypsin and lectin levels during the first 24 hours post-feeding. Any differences in trypanosome infection rates between the Lambwe Valley and Nguruman G. pallidipes probably result from other factors, such as sources of bloodmeals.
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    Determination of heavy metals in Kenyan cigarettes, tobacco leaves and intercropped plants by atomic absorption spectrophotometry.
    (2012-05-07) Mitei, Yulita C.
    Recent studies have indicated an increasing concern for the role that cadmium and lead play or are suspected to play in biological and physiological disorders such as emphysema of the lungs, renal tubular damage, cancer and cardiovascular diseases. Studies have revealed that cigarettes contain some heavy metals and that smoking involves the inhalation of small amounts of metals such as cadmium and lead. Since absorption from the lungs is usually complete, heavy smokers tend to absorb more of these metals. Given that both metals are accumulative in nature with long biological half-lives, smokers accumulate twice the amount accumulated by non-smokers. The study set out to find out whether Kenyan Smokers (Passive and active) are exposed to high levels of these heavy metals, to compare the levels in the cigarette tobacco with those in fresh tobacco leaves and to compare the levels in the fresh tobacco leaves with those in other crop plants grown in the same locality. In this study levels of cadmium, lead and Zinc were determined in fresh, cured/processed tobacco leaves, soil and other crop plants growing in the same locality. Levels in eight Kenyan cigarette brands currently in the market were also determined. For this the Spectr AA-10 Varian Atomic Absorption Spectrophotometer (AAS) (Varian Techtron Pty. Ltd. Australia) was utilized. The results reveal that the cadmium levels in Kenyan cigarettes compare well with those reported in the literature; However, the levels of lead and zinc were found to be higher than those reported in the literature. Also evident are higher than in the fresh tobacco leaves. This may indicate contamination during processing. The results also show that there is no significant differences in cadium and lead levels in fresh tobacco leaves and in the cured/processed leaves, thus the curing process does not seen to affect the metal levels in the tobacco leaves. This is however not the case with zinc. On the contrary the levels of zinc in fresh leaves are significantly higher than in the cured/processed leaves. Therefore the curing process seems to lower its levels. The levels of these heavy metals in other crop plants either higher or lower than those in tobacco leaves.
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    Antimicrobial efficacy of selected medicinal peanuts used by Kenyan herbal doctors
    (2012-05-07) Okemo, P. O.
    Herbal medicine is practiced by many countries of the world including Kenya, but scientific data to support the efficacy of herbal preparations has been lacking. Sixteen indigenous plants used by herbal doctors in Kenya were chosen from seven provinces and screened for antimicrobial activities using the disc diffusion method for preliminary selection. The most active plants, Entada abssyinica (Stem bark), Terminalia spinosa (Stem bark), Harrizonia abyssinica (roots), Ximenia caffra (roots), Azadirachta indica (stem bark and laves), and Spilanthes mauritiana (flowers and roots), were chosen for subsequent analysis, to determine efficacy and to identify a source of new possible antimicrobial agents. These plants were soxhlet extracted with methanol and tested for bioactivity. In the bioassay, the microtitre broth dilution method and the agar dilution method were compared to determine suitability for use. The microtitre method was found superior with a mean of 0.856 mg/ml compared to 2.958 mg/ml for the agar dilution method. Subsequently 110 strains of pathogenic bacteria from six genera were tested for activity using the microtitre broth dilution method. Their minimum inhibitory concentration (MICs) in mg/ml and minimum bactericidal concentrations (MBC's) in mg/ml were determined as a measure of their efficacy. The extracts had a bacteriostatic effect on Gram-negative bacteria and bactericidal effect on Gram-positive bacteria. Bacteria with special significance and some protozoa were examined separately. Mycobacteria species which were tested because of tuberculosis upsurgence in Human Immunodeficiency virus victims were found to be resistant to the extracts. Helicobacter pylori no known cure was killed by T. spinosa extracts (MIC range 62.5 - 500 g/ml). A protozoa, Acanthamoeba castellanii which causes granulomatous brain lesions has no known cure but responded to extracts of E. abyssinica, T. spinoss, X. caffra, A. indica and S. mauritiana when tested in vitro. Strains of pathogenic fungi from 2 genera Candida and Aspergilus were tested and found to be sensitive to more than 60% of the extracts used. As a result of this evaluation, four plant extracts E. abyssinica (stem bark), T. spinosa (stem bark), X. caffra (roots), and A. indica (stem bark) were found substantially bioactive. Candida albicans (ATCC 90873), E. coli (ATCC 29213) and a potent -lactamase producing organism, Pseudomonas aeruginosa (ATCC 27853), were used to perform time kill kinetics studies, in an effort to assess the rate and extent of the destruction of the said microorganisms by the above plant extracts. The mode of action was investigated by the kill kinetics experiments using an electron microscope. By this technique, any morphological changes in the microbial cell structure with continued exposure to the extracts would be detected. Results showed cell wall malfunction leading to failure to form septa and lysis of several microbial cells. Finally, the plant extracts were screened for the presence of coumarins, tannins saponins and other classes of compounds, which were considered active plant constituents. T. spinosa contained 75% of the classes of compounds screened, S. mauritiana 60%, H. abyssinica 56.3% and A. indica 56.3%.
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    Diversity and distribution of the afroalpine flora of Eastern Africa with special reference to the taxonomy of the genus pentaschistis (poaceae)
    (2013-08-14) Ahmed, Abdikadir Abdi
    The African tropic−alpine system, consists of a number of geographically separated ‘sky−islands’ and constitutes an excellent system in which to investigate the interaction between the geographical and ecological components of differentiation. The mountain systems harbouring the Afroalpine zone act as giant water towers that are source of almost all rivers that are an important source of water for domestic, industrial and agricultural use. Due to inaccessibility caused by extreme isolation and harsh conditions little research has been done on the diversity, species richness and evenness among other aspects in the Afroalpine zone. For effective conservation of these important zones it is important to understand their ecology. and the conservation status of the species of these zones. The aim of this study was to carry out ecological analysis of Afroalpine species in general and addresses species delimitation in the genus Pentaschistis. The vegetation of Afroalpine zone of Mount Kenya, Elgon, Kilimanjaro, Ruwenzori, Bale and Simen were sampled for ecological analysis and taxonomic revision of the genus Pentaschistis. A total of 75 plots (100 × 100 m) from five vegetation types were analysed using both univariate and multivariate analyses. From the study a total of 46 families, 124 genera and 278 species were recorded from rock outcrops, bogs, grassland, Dendrosenecio forest/woodland and Alchemilla vegetation communities. Six families, namely Asteraceae, Poaceae, Caryophyllaceae, Lamiaceae, Cyperaceae and Rosaceae constitute 56% of all the species sampled. Five communities were described from the vegetation types studied: Carex−Deschampsia bogs, Festuca−Pentaschistis grassland communities, Dendrosenecio−Alchemilla forest/woodland, Alchemilla communities and Helichrysum−Festuca−Koeleria−Pentaschistis rock outcrop communities. The species richness and diversity is higher in older mountains such as Mt. Simen, Bale and Elgon (over 20 MYBP) compared to younger mountains such as Mt. Kenya (3.5 MYBP), Kilimanjaro and Rwenzori (less than 3 MYBP) mountains. Similarly Ethiopian Mountains were more species rich and have higher diversity than mountains of East Africa. Simen was the most species rich as well as exhibiting highest species diversity while Rwenzori was the most species poor and with the least species diversity. The East Africa Mountains were similar both in their species composition and community structure, as were the Ethiopian Mountains. Factors such as the geographical distance, age, geological history, and position of the mountains along the Rift Valley, climatic and edaphic factors are thought to be responsible for the observed patterns. The five vegetation communities were recognizable from each other though rock outcrop and grassland communities were barely separable (R< 0.25). The rest of the vegetation communities were overlapping but separable especially between bogs vs. Dendrosenecio (R > 0.5). The mainly southern African grass genus Pentaschistis was represented on all Afro−alpine mountain systems but due to the complex ecological and geographical variation patterns, the number of species recognized is widely disputed. A classification based on a well–supported evolutionary hypothesis for the genus is necessary. In order to obtain this, morphological studies of both natural populations and herbarium specimens have been conducted during this study. A total of 38 characters were used to carry out phenetic analysis of 37 specimens from nine taxa. The results from morphological observation as well as the cluster and principal component analysis produced two main groupings viz. (1) the two widely distributed species P. borussica and the P. pictigluma species complex, and (2) two narrow endemics P. dolichochaeta and P. chrysurus. Similarly, phylogenetic analysis of three gene regions (TrnL-F, rpL-16 and ITS) based on 83 sequences were done in this study to infer the phylogeographic history of this genus. The results from this study indicate two independent events of colonization each corresponding roughly to the two broadly distributed species and the two narrow endemics. The morphological, phenetic and phylogenetic analysis of this study support the current taxonomic classification of the tropical species of the genus Pentaschistis.
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    Concentration of iron in laterites using in-situ carbonized biomass
    (2014-08-28) Njoroge, Peter Waithaka
    Iron occurs in more than 85 minerals. However, among these, only a few are important ores of the element. For economical extraction of iron, the iron ore must contain over 55% iron. These ores must be concentrated before putting them in a blast furnace. Kenya has widespread documented huge volumes of laterites. However the country spends huge amounts of money in importation of iron and iron products despite having these laterites that are rich in iron. This thesis describes the results of a study undertaken with the aim of finding out whether the level of iron in laterites (murram), can be increased to a level above 55% which can placed in a blast furnace for iron extraction. Samples for this study were obtained from selected murram quarries in, Kamahuha and Juja located in Murang‟a and Kiambu Counties respectively, in the Republic of Kenya. Total elemental analysis was carried out with particular interest on the levels of iron in both the raw and treated samples using Atomic Absorption Spectroscopy (AAS), X-Ray Flourescence Spectroscopy (XFRS) and EthylenediaminetetraaceticAcid (EDTA) Titrations. The mineralogical composition of both the raw and treated materials was determined using a Brucker D2 PhaserDiffractometer. The results of this study show that levels of iron in the raw laterites from Kamahuha ranged between 24-39% while those form Juja ranged between 12-17%. The iron in the raw laterites is present predominantly as the minerals goethite, FeO.OH and haematite, Fe2O3, as shown by presence of peaks at diffraction angles of 2θ = 21.51˚ and 2θ = 54.11˚respectively, which are attributed to these minerals. The concentration of iron in the laterites was done by heating a laterite/charcoal mixture in the temperature range 500-700oC in a ceramic container, under a slow current of air (0.5-0.7cm3/sec) from a compressed air cylinder. On cooling this mixture, the iron-containing mineral was readily picked with a permanent horse-shoe magnet (about 92milliteslas). The experiment was repeated using carbonized saw dust, leaves and dried potato peelings obtained from solid municipal waste in place of charcoal. The optimum ratio of biomass: laterite was found to be 1:20 by mass. After magnetic-separation iron was present predominantly as the mineral, magnetite Fe3O4, and had a broad diffraction peak at 2θ = 36˚.Furthermore, the percentage of iron in the magnet-separated product from both Kamahuha and Juja had increased to 55-62%. These results show that iron in the laterites can be increased to a level that can be used for iron extraction. Biomass from solid municipal waste can be used as a source of carbon monoxide to reduce goethite and hematite to magnetite. The use of biomass from the solid municipal waste also impacts positively on the environment. From the results obtained this process should be scaled up by setting up a pilot plant to concentrate iron laterites and determine the economic viability of the process.
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    Flouride levels in water sources of Gilgil area in Kenya: Deflouridation using locally available geomaterials
    (Kenyatta University, 2015) Wambu, Enos Wamalwa
    ABSTRACT High prevalence of fluorosis resulting from consumption of drinking water containing excessive fluoride levels continues to affect many communities in Kenya. Low in come rural communities are most affected because of inadequate water treatment and high costs of necessary medication. As part of the on-going search for efficient and ffordable water defluoridation protocol, which has intensified in the most recent past, soil dsorbents have attracted a near-global acclaim as the most promising low cost media for water defluoridation. Nevertheless, it is still unclear whether certain Kenyan clays and soil minerals could be applied as inexpensive adsorbents in dcfluoridation of household water. The present study was, therefore, designed to assess the capacities of selected locally available geomaterials (LAGs) to remove fluoride from water with a view to develop an efficient and affordable water defluoridation technology. The adsorbent materials, which included a naturally occurring siliceous mineral (NSIM), a diatomaceous earth (DIME), a ferric polymineral (pEPM) and iron enriched lateritic soils (FELS) were sampled from their natural deposits in Bungoma and Nakuru counties of Kenya. The minerals were pulverized to pass through O.S-mm sieves and less than 1.0-J.lm fractions isolated by mechanical agitation and sedimentation of the pulverized samples in doubly deionized water (DDW). After the initial pre-treatment in dilute HCI solution, the chemistry and mineralogy of the LAGs were analyzed by atomic absorption spectrophotometry (AAS) and by X-ray Diffraction Analysis (XRD). The fluoride adsorption properties of the LAGs were then assessed with respect to changes in initial fluoride concentration, contact time, mixing ratios, presence of interfering ions, and solution pH and temperature. The efficacy of the LAGs to sorb fluoride from natural high-fluoride water was verified in batch and column tests. Fluoride adsorption onto the acidified LAGs was found to be controlled by the mineralogy and chemical composition of the adsorbents as well as by the solution parameters. The equilibrium fluoride adsorption onto the LAGs was adequately fitted by the Langmuir and the Freundlich adsorption isotherms indicating heterogeneity in the fluoride adsorption mechanisms. Acidified DIME had highest fluoride adsorption capacity (51.1 mg/g) and the capacities of NSIM, FEPM and FELS to sorb fluoride from simulated batch solutions were in range of 10-13 mg/g. The adsorption kinetic data showed that for fluoride adsorption by NSIM and FEPM followed both pseudo-first order and pseudo-second order kinetic models. The adsorption of fluoride onto DIME could, however, be described by intraparticle diffusion kinetics whereas that for FELS by both the pseudo-second order and intraparticle diffusion models. Highest fluoride removal from high-fluoride natural water was achieved using FELS. Fluorides desorption from the LAGs, which was assessed using aqueous solutions of NaCI and Na2C03, demonstrated the reversibility of the processes. The LAGs showed good fluoride adsorption capacities and they could be utilised as inexpensive adsorbents to defluoridate high fluoride drinking waters and help to alleviate endemic of fluorosis among the communities. Results of this study will be useful as a basis for future scale up using these inexpensive materials as low-cost adsorbents to develop affordable technology for easy and safe defluoridation and sustainable cleaning of drinking water.
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    Efficacy and kinetics of adsorption of single and multiple heavy metal cations from aqueous solutions by fruit waste products
    (Kenyatta University, 2016-12) Nthiga, Esther Wanja
    Removal of toxic heavy metals from water has been a major challenge, especially in rural areas. Various methods have been used for this purpose; among them is biosorption based technology. The technology has been recognized as an economical and eco-friendly method for removal of toxic anions and cations from wastewater. Moreover, the efficacy of biomass in adsorption of cations and anions can be improved by different modifications, including treatment with sulphuric acid. Numerous approaches have been developed for adsorption of single ions in solution. However, toxic metallic or non-metallic ions rarely occur singly in wastewater. The presence of multiple ions in solution may often have agonistic or antagonistic effect on the efficiency of an adsorbent, and there is insufficient information on the efficacy of different methods for removing multiple ions. This study assessed the efficacy and mechanism of acid treated (modified) and raw (unmodified) biosorbents (derived from lemon, sweet yellow passion, banana, watermelon peels, and avocado seeds) for removal of toxic cations (Cd, Pb and Cu) from water. Functional groups of adsorbents were identified by mid-infrared spectroscopy (MIR) and their surface morphology was probed by scanning electron microscopy (SEM). the efficacy of each adsorbent was evaluated by quantifying the kinetics and levels of cations adsorbed at different pH of the solution, initial concentrations, contact time and adsorbent dose. Desorption experiments were conducted to determine the possibility of recovering ions and reusing the sorbents for next cycle of deployment. Experimental data of each metal ion was described by either Freundlich isotherm or Langmuir isotherm. The acid treated fruit peels and avocado seeds recorded higher efficacy as compared to raw adsorbents. Generally, acid treated watermelon peels demonstrated the highest uptake of 130.23 mg/g of Pb (II), followed by 114.234 mg/g of Cu (II) and 97.14 mg/g of Cd (II) ions. Further adsorption trials with binary and ternary metal blends on showed significant reductions in metal uptake capacities of evaluated adsorbents as compared to single metal systems. On account of metal preference, the selectivity order for metal ions towards the all the studied biomass was Pb (II) > Cu (II) > Cd (II). Time-course measurements indicated involvement of pseudo-second-order kinetics in adsorptions. Desorption efficacies were high on acid-treated adsorbents: 99.97 % ofPb(II) ions from acid treated avocado seeds; and 99.79 % of Cu(II) and 99.23 % of Cd (II) from acid treated watermelon peels. The results show good performance of the fruit peels and avocado seeds in adsorbing single and multiple metal ions, and the potential of using such wastes for purifying drinking and cooking water at household level.
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    Fabrication and characterization of magneto responsive carbon nanotube-infused polysulfone (cnt-ipsf) nanocomposites for water purification
    (2017-09) Silvanus, Shisia Kuboka
    The search for materials for purification of polluted water is growing daily with the advent of nanoparticles. This is particularly important because many populations of people in the developing countries lack clean water due to water pollution. Water pollutants such as heavy metals and polycyclic aromatic hydrocarbons (PAHs) are known to have adverse effects on humans and environment. This work investigated the potential of synthesized magnetoresponsive CNT polysulfone infused polymeric nanocomposites (CNT-IPSF) in water purification against heavy metals and polycyclic aromatic hydrocarbons (PAHs) pollution. Adsorption mechanism was studied at constant initial Pb(II) ion concentrations, nanocomposite dosage, contact time, and pH. Carbon nanotubes (CNTs) with internal diameters in the range of 20-30 nm were prepared via chemical vapour deposition (CVD) process. Magnetite and silica coated magnetite nanoparticles (NPs) prepared by solvothermal and sol gel methods respectively exhibited UV-Visible spectrometric spectra at about 395 nm and 396 nm respectively. Successfully synthesized Fe3O4 nanoparticles exhibited FT-IR absorption bands at 460 and 521 cm-1 which ascribed for the vibrations of Fe-O bond. X-ray diffraction analysis of core shell NPs showed strongest peak at D(311) plane, characteristic of a cubic spinel structure. The core shell nanoparticles obtained displayed a thin hysteresis loop having saturation magnetization of 2.2 emu g-1 with ferrimagnetic property. Removal efficiency of the synthesized CNT-PSF/Fe3O4 nanocomposite for Pb(II) ions and phenanthrenes was 69 % and 63 % respectively compared to that for a commercially available activated carbon which recorded 54 % and 53 % respectively. Adsorption of Pb(II) ions and phenanthrenes followed pseudo-second-order while Freundlich adsorption isotherm gave the best-fit for the two pollutants. Regeneration for Pb(II) ions of above 60 % and a gradual decrease in desorption efficiency for phenanthrenes of up to 50 % after three desorption cycles confirmed the reusability of the fabricated magnetoresponsive CNT IPSF/Fe3O4 nanocomposites. This study has developed a novel CNT-IPSF/Fe3O4 nanocomposite material with higher removal efficiency for water pollutants than commercially available activated carbon for use in water treatment.
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    Functionalized Geopolymers Derived From Clay and Rice Husk Ash for Removal of Selected Heavy Metals and Methylene Blue from Aqueous Solution
    (Kenyatta University, 2018) Maingi, Mukora Francis
    With the onset of industrialization, humanity has witnessed various ecological issues in the society and disturbance of ecosystem. Heavy metals and methylene blue are very toxic substances known to cause detrimental effects to human health when ingested even at low concentrations. Several techniques are available for removal of heavy metals, and dyes from the wastewater such as chemical precipitation, ion exchange, adsorption, membrane among others. Among these technologies adsorption is preferable for wastewater treatment due to its simplicity in design, high efficiency and availability of materials involved. Geopolymers are inorganic polymers and have been in use in construction industries as alternatives to ordinary portland cement but very little information is available on their use in environmental pollution management. This study aimed at synthesizing and functionalizing amorphous geopolymers from common clay and rice husk ash for use as adsorbents in removal of heavy metal ions and methylene blue from contaminated water. There is adequate literature indicating that clay minerals contain both silicates and alumina while rice husk ash contains substantial amounts of silica. This work therefore reports synthesis of geopolymers GP-1, GP-2 and GP-3 using clays and rice husk ash that were functionalized using citric acid and EDTA for use in adsorption of heavy metals and colour. Characterization of the geopolymers was done using FT-IR, EDS, XRD and SEM. Batch experiments using Pb (II), Cd (II), Zn (II) ions and methylene blue (MB) were done. FT-IR indicated presence of Al-O and Si-O bonds which are the finger prints of geopolymers. XRD analysis showed presence of amorphous phase between 18-36° (2θ) an indication that geopolymerization occurred. SEM analysis revealed the formation of a heterogeneous matrix which consists of a dense continuous gel with microcracks and voids on geopolymer adsorbents. The mean percentage uptakes of 99.32 ± 0.04, 99.74 ± 0.01, 91.33 ± 0.06 and 91.99 ± 0.57 of Pb (II), Cd (II), Zn (II) and MB were achieved respectively. Various equilibrium models were employed and from the correlation coefficients (R2 > 0.94), the data was found to fit best in Langmuir Freundlich model (Sips). The highest adsorption capacities of Pb (II), Cd (II), Zn (II) and MB were 326.5, 175.5, 169.9 and 20.74 mg/g respectively, attained using GP-3E. Increased adsorption of Pb (II), Cd (II), Zn (II) ions and MB was observed upon functionalization as well as when Si/Al ratio increased. Kinetic studies showed that a pseudo- second order model was more suitable than the first order in explaining the adsorption mechanism. This indicated that the adsorption transient behaviour used valence forces or exchangeable electrons and that chemisorption was more pronounced in the rate determining step. Thermodynamic studies revealed that the adsorption process was endothermic and physisorption since values of ΔH° obtained were < 40 kJ/mol. From the adsorption data, it’s evident that synthesized geopolymers are potential adsorbents for removal of heavy metals and MB and may be employed in wastewater management