School of Biological and Physical Scienceshttps://repository.maseno.ac.ke/handle/123456789/252024-03-28T21:16:11Z2024-03-28T21:16:11ZSynthesis and characterization of municipal waste incinerator fly ash based Geopolymers for the removal of Endosulfan from water: kinetics, isotherms, and thermodynamicsLUTTAH, Isaachttps://repository.maseno.ac.ke/handle/123456789/59972024-02-14T18:20:18Z2023-01-01T00:00:00ZSynthesis and characterization of municipal waste incinerator fly ash based Geopolymers for the removal of Endosulfan from water: kinetics, isotherms, and thermodynamics
LUTTAH, Isaac
Endosulfan is a broad spectrum organochlorine insecticide which acts as a contact poison for controlling a wide variety of insects. However, extensive and uncontrolled use of insecticides leads to water pollution. Conventionally, adsorption onto activated carbon is used to remove water pollutants from influent wastewater. A suitable adsorbent must be cheap, possess high adsorption capacity, fast adsorption kinetics and recyclable among other properties. Geopolymers are emerging low-cost and efficient adsorbents for removal of various contaminants from water. The performance of the geopolymers varies with both sorption conditions and adsorbent structural and textural characteristics, which are controlled by several factors such as; the precursor material and the preparation conditions. While silicate to NaOH ratios affect mechanical properties of geopolymers for construction purposes, the impact of silicate to NaOH ratios on the adsorptive performance of geopolymers is unknown. Furthermore, although research has been done on remediation of pesticides from water using various adsorbents, no article has reported the use of solid waste incinerator fly ash MWFA-based geopolymers especially on their synthesis and/or application as adsorbent for endosulfan removal from water. The present work investigated the adsorption of endosulfan on alkaline activated geopolymers, synthesized from MWFA. Since there is no reported theory for predicting the geopolymer sorption capacity and adsorption rate based on precursor materials and silicate to NaOH ratios conditions, this leaves a clear gap in our understanding of the role of these factors. The objective of this study was to synthesize MWFA-based geopolymers and evaluate the effect of sodium silicate to NaOH ratio of the activator solution on morphology, chemical composition, and adsorptive performance (adsorption capacity and mechanism) in batch-mode. Alkali-activated MWFA-based geopolymers, GPA, GPB, and GPC, were synthesized using 0.17, 0.21 and 0.24 sodium silicate to sodium hydroxide mole ratios, respectively. The geopolymers were applied in the removal of endosulfan from water. The adsorbents were characterized by XRD, SEM-EDX, and FTIR. Variation of sodium silicate to sodium hydroxide mole ratios resulted in morphologically distinguishable geopolymers with different compositions. Adsorption experiments were done at different parameters such as initial endosulfan concentration, contact time, pH, geopolymer dosage and temperature. The adsorption equilibrium data were best described by Langmuir isotherm. The maximum adsorption capacities increased with an increase in sodium silicate to sodium hydroxide mole ratios in the order 1.872, 15.899, 16.970, and 20.010 mg/g for MWFA, GPA, GPB, and GPC, respectively. The kinetic data were best described by the pseudo-first-order model wherein the adsorption rate (k1) was independent of the sodium silicate to sodium hydroxide mole ratio and the geopolymer composition. The thermodynamic parameters, that is enthalpy (∆H > 0), Gibbs free energy (∆G < 0), entropy (∆S > 0), and activation energy (Ea > 0) show that the processes were endothermic, spontaneous, physical (Ea and ∆H < 40 kJ/mol) and entropy-driven. Alkalination was beneficial since the geopolymers had a higher adsorption capacity (~8-10 times) and affinity for endosulfan (~30 times) than the precursor material (MWFA). The adsorption mechanism entailed electrostatic interactions and hydrogen bonding. Increase in sodium silicate to NaOH ratio increases the adsorption capacity of the geopolymers for endosulfan. The MWFA-based geopolymers prepared with high silicate to NaOH ratios are recommended as alternative high adsorbing materials for wastewater treatment and a strategy for the valorization of MWFA.
Master's Thesis
2023-01-01T00:00:00ZMolecular determination of Plasmodium falciparum parasites with histidine-rich protein 2/3 gene deletions in a holoendemic area, Siaya county, western KenyaACHIENG’, Sharley Wasenahttps://repository.maseno.ac.ke/handle/123456789/59762023-12-22T07:02:31Z2023-01-01T00:00:00ZMolecular determination of Plasmodium falciparum parasites with histidine-rich protein 2/3 gene deletions in a holoendemic area, Siaya county, western Kenya
ACHIENG’, Sharley Wasena
Malaria remains endemic in western Kenya despite the various control interventions. Accurate diagnosis is key to the treatment and control of malaria. As such, the World Health Organization (WHO) recommends parasite-based confirmation of malaria prior to treatment. Plasmodium falciparum Histidine Rich Protein 2 (PfHRP2) based malaria Rapid Diagnostic tests (mRDTs) kits are commonly used throughout western Kenya as an alternative to microscopy in malaria diagnosis. However, the emergence of P. falciparum isolates with HRP2/3 deletions has threatened the sensitivity and performance of the mRDT kits. In western Kenya, a high transmission holoendemic area, polyclonal P. falciparum infection could be present but masked by the wild type gene. This may lead to both underestimation of deletion prevalence and increase in the spread of parasites with deletion. False negative mRDTs pose a public health threat towards malaria treatment and elimination progress. This is because the proportion of malaria infected patients having these gene deletions will go undetected by the PfHRP2-mRDTs, and therefore remain untreated. Siaya County borders western Uganda, an area where massive reports of HRP2/3 gene deletions have been reported and hence the need to conduct HRP2 surveillance in the study area. The study therefore investigated PfHRP2/3 deletions in a paediatric cohort from Siaya county, in western Kenya. Specifically, the study determined the prevalence of PfHRP2/3 deletion and the relative strain abundance of deleted strains in polyclonal infections, compared P. falciparum parasite densities estimated by qPCR and microscopy and evaluated the performance of the mRDT and microscopy techniques that routinely used for malaria diagnosis in Siaya County, western Kenya. The study being retrospective in nature, archived RBC pellets extracted from EDTA blood of children (n=219) who were previously enrolled in the study was used for DNA extraction. In order to achieve all the objectives, the study utilized one-step multiplex quantitative polymerase chain reaction (qPCR). The multiplex qPCR was designed using three differently labelled TaqMan assays detecting the PfHRP2 (PF3D7_0831800) and PfHRP3 (PF3D7_1372200) genes. Overall, PfHRP2/3 deletions were detected in 12 (5.6%) parasite isolates. The PfHRP2 monoclonal deleted strains were present in 2 isolates (1%) isolates while no parasite isolates harbored PfHRP3 single deletion. Further, 9 (4.1%) isolates had deleted PfHRP2 and 1 (0.5%) had PfHRP3 deleted but were masked in polyclonal infection. The average relative abundance of PfHRP2 deleted parasites was 9.6% while wild type was 90.4% in polyclonal infections. The multiplex qPCR demonstrated a higher ability in detecting malaria parasites compared to microscopy with median (IQR) of 8.28E4 (2.75E6) and 6.24E3 (2.45E4) respectively (P≤0.001). Further, there was a positive correlation between parasite detection by qPCR and microscopy
(r=0.59, P≤0.001). On evaluation of the performance of clinical diagnostic techniques used in Siaya County Referral Hospital (SCRH), microscopy demonstrated a higher diagnostic sensitivity of 97.6% (95%CI, 89.8-105.0) and specificity of 26.0% (95%CI, 22.4-29.6) as compared to mRDT. Cohen Kappa’s test revealed a fair agreement between microscopy and qPCR, (k=0.30, P≤0.001). The study provides evidence of PfHRP2 deleted strains including those that are masked in polyclonal infections and their relative abundance in Siaya County. Further the study highlights microscopy as a more sensitive and specific technique in detecting malaria infection as compared to mRDT test.
Master's Thesis
2023-01-01T00:00:00ZPrevalence and antibiotic susceptibility patterns of cotrimoxazole resistant bacterial uropathogens from Hiv patients attending Maseno mission hospital, western kenyaMUSASIA, Philip Sakwahttps://repository.maseno.ac.ke/handle/123456789/59732023-12-22T06:39:47Z2023-01-01T00:00:00ZPrevalence and antibiotic susceptibility patterns of cotrimoxazole resistant bacterial uropathogens from Hiv patients attending Maseno mission hospital, western kenya
MUSASIA, Philip Sakwa
Urinary tract infections (UTI) are inflammatory disorders within the urinary system due to presence of pathogenic microorganisms. Taking advantage of lowered immunity in Human Immuno-deficiency Virus (HIV) patients, bacterial UTI globally contribute up to 60% of opportunistic infections (OI). Previous HIV related (OI) studies concentrated on malaria and sexually transmitted diseases ignoring UTI. Owing to its wide interceptive range, cotrimoxazole was recommended for prophylaxis by world health organization and has been standard against opportunistic infections. However, with prolonged use, bacterial resistance is being reported. Uncertainty of UTI management following rising reports of bacterial resistance to commonly used drugs in AIDS era is real. This hospital based descriptive study investigated prevalence and antibiotic susceptibility patterns of cotrimoxazole resistant bacterial uropathogens from HIV patients attending Maseno mission hospital in western Kenya where treatment is blindly based on chance and history during clinic visits without laboratory testing. Specifically described bacterial UTI prevalence, determined their response to cotrimoxazole and established antibiotic susceptibility patterns. At interval of six, 354 participants were systematically selected from population of 2000. Mid-stream urine was cultured on cysteine lactose electrolyte deficiency agar and samples obtaining >105 colony forming units determined by colony counters were biochemically characterized before being subjected to cotrimoxazole broth dilution sensitivity testing. Isolates not responding to cotrimoxazole were subjected to disc diffusion susceptibility testing in accordance with Clinical Laboratory Standards Institute’s guidelines. Tables, graphs and charts were used to present generated data which was analyzed alongside structured questionnaire captured demographic information. Prevalence of UTI among HIV patients was 117(33%) where 75.4% originated from females and 25.6% males with Escherichia coli (54.7%) being most encountered. Chi square analysis of bacterial responses to cotrimoxazole evaluated at 95 % confidence level was statistically significant at P<0.05 (x)2 (5)=14.3, p< 0.005 with an average susceptibility of 46.6%. Significantly, study results will serve as reference point for future researchers and medics, formed policy reevaluation for prophylaxis program and enhanced better OI management by establishing susceptibility patterns and suitable antibiograms. Study recommended for constant monitoring profile aetiological bacteria, periodic surveillance of for prophylactic drug and practicing scientifically determined treatment recommending most susceptible gentamicin (80.3%) empirical antibiotic for region with 53.4% resistance
Master's Thesis
2023-01-01T00:00:00ZCorrelation between equatorial electrojet and the occurrence of equatorial ionisation anomaly over the East African region during the solar minimum period 2008-2009MILIMU, Anekha Hanningtonhttps://repository.maseno.ac.ke/handle/123456789/59662023-12-22T06:06:26Z2023-01-01T00:00:00ZCorrelation between equatorial electrojet and the occurrence of equatorial ionisation anomaly over the East African region during the solar minimum period 2008-2009
MILIMU, Anekha Hannington
In the electron density distribution at the low-latitude ionosphere, equatorial electrodynamics plays a critical role such as forecasting the dynamics and fluctuations of ionospheric plasma densities. The equatorial electrojet (EEJ) and the equatorial ionization anomaly (EIA) are two major phenomena of equatorial electrodynamics. Studies have been carried out on the strength of EEJ as well as the EIA. However, the following gaps still exist: most studies have been done in Indian and American regions during maximum solar years; yet ionospheric dynamics have a dependence on the longitude; correlations have also not been done during both geomagnetically quiet and disturbed conditions. The correlation between EEJ and EIA was required since EEJ is one of the systems that lift plasma in equatorial regions, causing Equatorial Ionization Anomaly, which suggests a connection between EEJ and EIA. Since it is necessary to get a complete picture during both geomagnetically quiet and disturbed conditions, therefore, the problem of the study is that strong scintillations affect communication and navigation systems. Thus, there is a need to investigate the relationship between EEJ and EIA since they are important for ionospheric space weather and also this will help the development of models that can be used to forecast or nowcast scintillations. Based on the aforesaid knowledge gap the problem of this study is on EEJ's impact on the development of the EIA during the low solar activity period over the East African region. Based on this problem the objectives of the study were (i) To determine the strength of EEJ, (ii) To quantify the strength of EIA and (iii) To analyze the correlation between EEJ and EIA. This study used a pair of International Real-time Magnetic Observatory Network (INTERMAGNET) magnetometers located in Addis Ababa (geographic 9.05°N, 38.76°E, geomagnetic 0.16°N, 110.45°E), the African Meridian B-field Education and Research (AMBER) station in Adigrat (geographic 14.26°N, 39.45°E, geomagnetic 6.1°N, 111.04°E) both in Ethiopia and the total electron content (TEC) derived from a set of International Global Navigation Satellite System (GNSS) signals (IGS) receivers within the East African region. The data used during this period was for both geomagnetically disturbed and quiet conditions. The difference in the horizontal component of the geomagnetic field seen by two ground-based magnetometers was used to estimate the EEJ strength. In determining the EIA strength over the region, TEC over the crest to that above the trough was determined to be in a certain ratio. The peak value of EEJ is 110nT and it occurs between 10:00 and 14:00 LT for geomagnetically quiet conditions. This is due to the high rate of photoionization during this period. These variations in the amplitude of EEJ with time and months is attributed to the monthly movement of the Sq foci northward and equatorward in a given year. The EIA’s peak during geomagnetically quiet days is 1.45 and it was recorded between 20:00 – 22:00LT while the peak of EIA during geomagnetically disturbed days is 1.2 and it occurred at 20:00LT. The correlation coefficients were found to vary from moderate to strongest during geomagnetically quiet conditions, ranging from 0.58 to 0.74. During geomagnetically disturbed conditions, the correlation coefficient ranges from 0.28 to 0.45. The significant linear link between EEJ and EIA is caused by the independent increase in the eastward electric field and photo-ionization on TEC. Most panels showed that the ratio of Crest (CT) to trough (TEC) > 1. This research presents patterns in the EEJ and EIA strength over East Africa during the solar minimum period. Since EEJ and EIA influences the occurrence of ionospheric irregularities which in turn lead to scintillations of communication and navigation signals, we recommend simultaneous analysis of EEJ, EIA and scintillation data. This would reveal the influence of EEJ and EIA on the occurrence of scintillations.
Master'S Thesis
2023-01-01T00:00:00ZAntimicrobial activities of extracts and isolates from Senna didymobotrya flowers.ATIENO, Hellen Onyangohttps://repository.maseno.ac.ke/handle/123456789/59602023-12-21T16:50:20Z2023-01-01T00:00:00ZAntimicrobial activities of extracts and isolates from Senna didymobotrya flowers.
ATIENO, Hellen Onyango
The emerging trends in pathogenic microorganisms becoming resistant to available antibiotics coupled with the evolution of new strains of pathogens causing diseases, is a major concern to the global health community and this requires urgent remedy. Prolonged treatment with conventional antimicrobial drugs has led to their toxicities among patients and therefore, for effective treatment of diseases caused by pathogenic microbes, search for new pharmaceuticals or some potential sources of novel drugs are necessary. Medicinal plants commonly used by various communities could be potential sources for bioprospection to help in the fight against this menace. This study focused on evaluating the antimicrobial activity of Senna didymobotrya flowers (Caesalpiniaceae), a plant widely used in Kenyan folklore medicine to manage bacterial and fungal infections. In parts of Kisumu, the flowers of the plant are used to manage diarrhoea and itching of the skin. Although the flowers are traditionally used by herbalists to manage microbial infections, very little work has been done to evaluate the efficacy of the extracts against pathogenic microbes. In addition, compounds responsible for the antimicrobial activity in the flowers have not been isolated and characterized. The objectives of this study were to evaluate the extracts and isolated compounds from flowers for antifungal and antibacterial activities. The dry and pulverized flowers of the plant were sequentially extracted with n-hexane, ethyl acetate and methanol. The methanol extract significantly (P≤0.05) inhibited M. gypseum (MIC 3.9µg/ml), T. mentagrophyte (MIC 7.8µg/ml), K. pneumoniae and C. albicans (MIC value 31.3 µg/ml each). This was followed by ethylacetate extract which gave moderate results against M. gypseum (MIC 15.6µg/ml), S. faecalis, B. anthracais, C. albicans and T. mentagrophyte (MIC value 62.5 µg/ml each). n-Hexane extract afforded MIC values ranging between 125 µg/ml to over 250 µg/ml. Fractionation of the various extracts led to the isolation of twelve compounds whose structures were determined using physical and spectroscopic methods as well as comparison with literature data. The compounds were: chrysophanol (7), physcion (9), emodin (10), quercetin (253), β-sitosterol (302), stigmasterol (303), lupeol (323), betulinic acid (324), oleanolic acid (335), 4’, 5-dihydroxystilbene-3-O-glucoside (336), 5-hydroxyflavone (337) and 7-hydroxyflavone (338). All the isolated compounds were screened for antimicrobial activities.The most active metabolite was emodin which gave a MIC in the range 15.6-250 µg/ml against all the microorganisms tested except E. coli (MIC >250 µg/ml). 7-Hydroxyflavone also afforded good results by displaying MIC values in the range 31.3-250 µg/ml against all microorganisms that were tested. The least active metabolites were β-sitosterol and stigmasterol which were observed to show mild activities against S. aureus (MIC 250 µg/ml). Activities of the three extracts and isolated compounds against the tested pathogenic microbes were significantly (P≤0.05) lower compared to the activities exhibited by kanamycin and fluconazole which were used as standards against bacteria and fungi, respectively. This study has authenticated the traditional use of S.didymobotrya flowers in the management of bacterial and fungal infections. It has also identified the individual compounds responsible for the activities. Compounds that exhibited high antimicrobial activities such as emodin, and 7-hydroxyflavone may be developed into formulations to be used as antimicrobials.
Master's Thesis
2023-01-01T00:00:00ZSero-prevalence of Brucellosis and associated risk factors to Brucella pathogen in Tiaty, Baringo County, KenyaOUMA, Dickens Oloohttps://repository.maseno.ac.ke/handle/123456789/59592023-12-21T16:43:28Z2023-01-01T00:00:00ZSero-prevalence of Brucellosis and associated risk factors to Brucella pathogen in Tiaty, Baringo County, Kenya
OUMA, Dickens Oloo
Brucellosis is a global zoonotic disease caused by Brucella pathogen, which affects man and animals. The disease has been reported across the world including Kenya. Information regarding the sero-prevalence and risk factors of brucellosis in camels in the pastoral Tiaty is still scanty despite several reported loss of camels due to zoonotic diseases. The main objective of this study was to investigate sero-prevalence of brucellosis, and the Risk factors associated with Brucella pathogen infections in Tiaty Sub-county, Baringo County. Thus a cross-sectional study was conducted in the study area whereby a total of 105 sera samples were collected from camels i five study locations, dominated by camel farmers using a multi stage sampling technique. The samples were tested to detect antibodies against Brucella by competitive immunosorbent assay (cELISA) as per the manufacturer’s instructions. In addition, data, on location of camels, history of retained placenta or abortion, gender, and age was gathered using a questionnaire. DNA extraction and purification was done on the positive samples using the Norgen bacterial genomic DNA isolation kit, then the quality and quantity of DNA were determined according to the manufacturer’s instructions. The data on risk factors was analyzed using chi-squared test (X2) at 95% confidence interval (CI) to investigate the relationship between brucellosis and the risk factors. The overall sero-prevalence of 20.0% was reported in camels. The percentage sero-prevalence per study location indicated that Ribikwo had the highest seroprevalence of 38.1% while Silale recorded the least 14.3%. Chemolingot, Lolyamorok and Kollowa locations recorded 28.6%, 19.0% and 0.0% respectively. The proportions of seropositivity in the study locations were significantly higher which revealed a significant association between sero-positivity of camel brucellosis with the location, (p ═ 0.037). It was revealed that brucellosis was associated with age and gender of the camels, further logistic regression analysis on gender revealed that there was 4 times more likelihood of females being seropositive as compared to males (OR = 4.329, 95% CI = 0.971-19.307, P-value 0.050). Further, logistic regression analysis on age revealed that there was 5.8 times more likelihood of seropositivity of brucellosis occurring in camels < 2 years old compared to those aged 2-3 years and those over 3 years old (OR = 5.845, 95% CI = 1.340-25.489, P-value 0.019). History of abortion was found to have no significant association with camel brucellosis which implies that abortions in camels is mainly not linked to brucellosis. Further logistic regression analysis on the age of the camels found out that there is 0.5 times more likelihood of brucellosis occurring in camels with history of abortion (OR = 0.522, 95% CI = 0.118-2.305, P-value 0.391). The high sero-prevalence reported in this study incriminates cattle, sheep and goats as the source of infection since they are reared in close association with camels. The determinant of brucellosis seropositivity were gender and age of camels. Therefore, brucellosis control programs targeting multiple species cattle, goats’ sheep, and camel should be formulated to curb spread of the disease.
Master's Thesis
2023-01-01T00:00:00ZAssociation between hiv-1 subtypes and drug resistance to first line therapy among individuals with advanced disease in Homa bay county, KenyaNYAKUNDI, Nelson Mokayhttps://repository.maseno.ac.ke/handle/123456789/59582023-12-21T15:32:10Z2023-01-01T00:00:00ZAssociation between hiv-1 subtypes and drug resistance to first line therapy among individuals with advanced disease in Homa bay county, Kenya
NYAKUNDI, Nelson Mokay
Human Immunodeficiency Virus-1 remains a public health threat globally, and although antiretroviral therapy has greatly improved the lives of people living with HIV, challenges persist due to high HIV genetic diversity and drug resistance. Analysis of HIV-1 subtypes over time demonstrates high subtype diversity and dynamic changes with variations in drug resistance among different HIV-1 subtypes. Homa Bay County carries one of the highest HIV-1 burdens worldwide, yet up-to-date information on circulating subtypes and subtype-specific drug resistance is lacking. The general objective of this study was to determine the association between HIV-1 subtypes and drug resistance to first-line ART among individuals with advanced disease in Homa Bay County. The study specifically sought to characterize HIV-1 subtypes and recombinants, to determine HIV-1 subtype-specific drug-resistance mutations, and to determine HIV-1 subtype-specific polymorphisms associated with drug resistance among HIV-1 patients on first-line ART in Homa Bay County, Kenya. A facility-based, cross-sectional survey was conducted, enrolling individuals aged 15 years and above, with advanced HIV-1 disease, and who had been on first-line ART for at least 6 months. The sample size determined using Cochran's formula was 70 participants. Plasma samples were analyzed using CAP/CTM real-time PCR for HIV-1 viral load and genotyping was performed on dried blood spots for samples with a viral load ≥1000 copies/mL. A genetic analysis of a 1,084-bp fragment of the HIV-1 pol gene encoding amino acids 6-99 of the protease (PR) and 1-251 of the reverse transcriptase (RT) region from 65 participants was performed using an in-house assay. Drug resistance was determined using the Stanford University HIV Database. Subtypes were identified using phylogenetic analysis and REGA subtyping tool. Fisher’s exact test was used to assess the association between subtypes and drug-resistance mutations. Samples with a significant association were subjected to logistic regression analysis, controlling for regimen. The findings revealed that subtype A1 was most prevalent in 46 patients (70.8%), with lower prevalence rates for subtype D (n=9, 13.8%), recombinants (n=6, 9.2%) and A2 (n=4, 6.2%). No statistically significant association was observed between subtypes and nucleoside reverse transcriptase inhibitor (NRTI) mutations or polymorphisms. However, a notable finding was the lower likelihood of observing NNRTI mutations K101E/H and Y181C/I/V, associated with high-level resistance to Nevirapine (NVP) and Efavirenz (EFV), in subtype A1 than in other subtypes (OR=0.14, 95% CI=0.03-0.60 and OR=0.21, 95% CI=0.06-0.72, respectively). This analysis found that HIV-1 subtypes are associated with resistance mutations, with K101 and Y181 less likely in subtype A. This suggests that areas with a high prevalence of subtype A1 may experience reduced compromised efficacy of NVP and EFV as first-line ART options. This implies that ART choice may need to be tailored to the HIV-1 subtypes. However, further investigations with large sample sizes and longitudinal designs are warranted to confirm this and assess the clinical impact of these subtype-specific differences to inform ART regimen policies effectively.
Master's Thesis
2023-01-01T00:00:00ZEvaluation of anti-leishmanial activities of Olea europaea, Kigelia africana, Terminalia mollis, Croton macrostachyus, and Bridella micrantha extractsWAFULA, Dennis Mukhwanahttps://repository.maseno.ac.ke/handle/123456789/59142023-12-19T16:10:10Z2023-01-01T00:00:00ZEvaluation of anti-leishmanial activities of Olea europaea, Kigelia africana, Terminalia mollis, Croton macrostachyus, and Bridella micrantha extracts
WAFULA, Dennis Mukhwana
Leishmaniasis pose a significant medical concern worldwide which if left untreated, can be fatal. Although expensive and toxic, pentavalent antimonial drugs are the first-line treatment for leishmaniasis raising the need to find an alternative. Plants extracts contain several bioactive compounds that may offer alternative therapeutic signifcance to already developed antileismanial drugs. Based on folkloric information, a number of plants such as Olea europaea, Kigelia africana, Terminalia mollis, Croton macrostachyus, and Bridella micrantha are used to cure Leishmaniasis in the endemic regions in Baringo County. However, no studies have been done to find out the phytochemical compounds, as well as the anti-leishmanial properties. The aim of this study was to investigate the anti-leishmanial activity of Olea europaea, Kigelia africana, Terminalia mollis, Croton macrostachyus, and Bridella micrantha extracts. The plants were collected from Marigat in Baringo County (Kenya), air-dried, ground into fine particles, and extracted at the KEMRI Center for Traditional Medicine and Drug Research. Completely randomized design (CRD) was used in the in vivo studies. In vitro investigations were carried on L. major promastigotes to determine inhibitory concentrations (IC50) and Minimum Inhibition Concentrations (MIC) and toxicity on Vero cells. A total of 35 mice, 6 in each experimental group were used. For in vivo bioassays, the mice were injected intradermally on the left posterior footpad with 1×106 stationary phase flagellate forms of cultured L. major, and then housed for 4 weeks to allow disease manifestation. Differences between treatment groups exposed to different drugs were examined using logistic regression for each parameter studied. Phytochemical components of bark of the plants contain glycoside, terpenoids, tannins, flavonoids, steroids, and saponins. T. mollis contaned higher concentration of tannins, phenols, alkaloids, and anthraquinone. The crude extracts from the plants significantly inhibited promastogote and amastigote growth (P ˂ 0.05) after 24 hours of exposure, with the standard drug (Amphotericin B) being the most effective, while T. mollis was highly potent on amastigote among the plant extracts, then, C. macrostachyus, while O. europeae was least effective. Among the plant extracts, T. mollis had the highest efficacy (IC50 = 85.5 mg/l) in promastigote, while the least effective was O. europaea. In amastigotes, T. mollis exhibited the highest anti-amastigote activity (IC50 = 96.5 mg/l). The Leishman Donovan Units (LDU) of the L. major infection was lowest (0.12 × 106) in L. major-infected mice treated with T. mollis, while that of O. europeae was highest (4.12 × 106). After four weeks, mice administered with T. mollis demonstrated the greatest decrease in lesion diameter (0.68 ± 0.07 mm). Therapy with T. mollis, resulted in a considerably greater lesion reduction in mice. After 4 weeks of treatment, mice administered with O. europeae had the smallest reduction in lesion diameters of all the drugs examined. After 24 hours of treatment, the different drugs significantly influenced mammalian cell survival (P ˂ 0.05), with percentage cell viability of herbal medications, B. microstachyus, and O. africana causing the most toxic effects. It is concluded that among the extracts from the back of the five test plants, T. mollis at concentraton 85.5 to 96 mg/l was the most effective against Leishmania infection. Over all, the results obtained from the crude extracts screening, suggest that these may be promising sources for the development of new drugs for controlling leishmaniasis. The study recommends the use of T. mollis as the most effective plant extract in management of leishmaniases.
PhD Theses
2023-01-01T00:00:00ZPhytochemical evaluation of Ocimum kilimandscharicum GUERKE, Gnidia subcordata MEISN AND Annona mucosa jacq leaves for secondary metabolites and their insecticidal activities against Sitophilus zeamais and Prostephanus truncatus.MULIANGA, Albert Makenzihttps://repository.maseno.ac.ke/handle/123456789/59012023-12-18T16:32:18Z2023-01-01T00:00:00ZPhytochemical evaluation of Ocimum kilimandscharicum GUERKE, Gnidia subcordata MEISN AND Annona mucosa jacq leaves for secondary metabolites and their insecticidal activities against Sitophilus zeamais and Prostephanus truncatus.
MULIANGA, Albert Makenzi
Global food security of which maize is a major component is threatened by food loss due to storage insect pests. Sitophilus zeamais and Prostephanus truncatus cause stored maize losses of 20% world wide and 45% in Africa. Synthetic insecticides though effective in control of insect pests, insect resistance and the adverse side effects associated with the insecticides calls for search of effective and safe botanical insecticides. Ocimum kilimandscharicum, Gnidia subcordata and Annona mucosa leaves have been used traditionally to control insect pests. Efficacy of their crude extracts and active principles occasioning their uses are however not documented. This work evaluated insecticidal activities of the plants’ leaf extracts against S. zeamais and P. truncatus, isolated and characterised pure isolates and evaluated the pure isolates for their insecticidal activity against the two insects. Powdered plant leaves were separately sequentially soaked in n-hexane, ethyl acetate and methanol then filtered, concentrated and subjected to column chromatography fractionation with eluents of differing polarities and then thin layer chromatography. Structural elucidation of isolated compounds was done using physical and spectroscopic methods including NMR, IR, UV-VIS, mass spectrometry and comparison with literature data. Extracts and pure isolates were assayed for toxicity and antifeedant activities against S. zeamais and P. truncatus. Deltamethrine and azadirachtin were used as positive controls. Gnidia subcordata methanol extracts exhibited the highest contact toxicity and antifeedant activities against S. zeamais: LC50 = 27.03 μg/mL, AFI50 = 20.47 μg/mL and P. truncatus: LC50 =22.55 μg/mL, AFI50 = 20.99 μg/mL, which compared favourably with activities of the positive controls. Gnidia subcordata yielded β-amyrin acetate (199), 3β-hydroxy-11-oxoolean-12-ene (200), dihydronitidine (201), dihydrochelerythrine (202), gedunin (203), obacunone (204), nagilactone (205), quercetin (140), kaempferol-3-O-β-galactoside (206) and 4', 5-dihydroxystilbene-3-O-β-glucoside (207). n-Eicosanol (208), friedelin (209), stigmasterol (6), lupeol (49), 2α-hydroxy-3-oxodammar-20, 24-diene (210), 2α, 3β-dihydroxy dammar-20, 24-diene (211), chrysin (212), apigenin (144), fisetin (213), quercetin (140) and apigenin-7-O-neohesperidoside (214) were isolated from Ocimum kilimandscharicum. Annona mucosa yielded; α-amyrin acetate (215), β-sitosterol (96), 3α, 24-diacetoxy-12-oleanene (216),3-oxo-11β-hydroxyurs-12-ene (217), (3R,20S)-3-acetoxy-20-hydroxydammar-24-ene (218), 3β-acetoxy oleanolic acid (219), 3β-acetoxytirucallic acid (220), quercetin (140), oleanolic acid (4), quercetin 3-O-β-D-arabinoside (221) andquercetin-3-O-β-D-glucoside (222).Compounds 210, 211 and 216 are new. Among the isolated compounds, 203 had the highest contact toxicity activities LC50 15.68 and 16.99μg/mL while 222 had the highest antifeedant activities AFI50 14.93and 16.84 μg/mL., against S. zeamais and P. truncatus respectively, which compared well with activities of the positive controls. This study has validated the traditional use of the plants in stored maize protection against insect pests. It has also identified the individual compounds responsible for the activities. These compounds can be developed into formulations individually or as mixtures to control S. zeamais and P. truncatus in maize.
PhD Theses
2023-01-01T00:00:00ZExperimental and computational studies of properties of thin films of cadmium-tin-oxide for manufacture of micro-electromechanical systems and for noise controlONGWEN, Nicholas Ogadahttps://repository.maseno.ac.ke/handle/123456789/57412023-06-22T15:44:34Z2022-01-01T00:00:00ZExperimental and computational studies of properties of thin films of cadmium-tin-oxide for manufacture of micro-electromechanical systems and for noise control
ONGWEN, Nicholas Ogada
The recent advancement in electronics have stimulated the high demand for semiconductor substrate materials for the printing of electronic circuits, some of which are used in the Micro-Electromechanical Systems (MEMS) devices. The most commonly used substrate for the printing of these devices is silicon (Si), which is preferred because, compared to the other semiconductor substrate materials like silicon nitride and gallium arsenide, it: Has better electrical, mechanical and thermal properties that are desirable for the fabrication of MEMS devices; is readily available, and is also relatively cheaper. Despite the advantages above, Si has serious drawbacks, including rarely occurring as a pure element and being brittle, which call for alternative substrate materials such as cadmium tin oxide (CTO), whose thin films (TFs) have been studied and proved to possess excellent optical and electrical properties, as well as flexibility. However, the mechanical and thermal properties of CTO have not been explored extensively. This study employed ab initio calculations to determine the mechanical and thermal properties of CTO. The specific objectives of the study were: i) to find out the effect of concentration of cadmium and tin on the structural properties of CTO, (ii) to develop a simplified method that applies stress and strain in calculating elastic constants of materials, (iii) to find out the effect of concentration of cadmium and tin on the mechanical properties of CTO, and (iv) to find out the effect of concentration of cadmium and tin on the thermal properties of CTO. The TFs of CTO were prepared by dissolving cadmium chloride and tin II chloride separately in distilled water to form 0.4 M of each solution. The two solutions were then mixed at ratios of 1:5, 2:4, 3:3 4:2 and 5:1 by volume. The final solutions were then sprayed onto the preheated microscope glass substrates by spray pyrolysis at a temperature of 450 °C. The measurement of film thickness was done using surface profiler, the X-Ray diffraction measurements were taken using Expert Pro from 2θ = 10-70° at a step of 0.02°, the chemical composition was measured using X-Ray Fluorescence. The ab initio calculations were done using density functional theory with PBESOL functionals as implemented in the Quantum Espresso code. Stress-strain method was developed for the study of mechanical properties. The outcome of the study showed that all the properties of CTO are very sensitive to the number of cadmium atoms. The optimum properties obtained were: crystallite size of 60.75 nm, density of 7.636 g/cm3, bulk modulus of 149.1 GPa, shear modulus of 53.2 GPa, Young’s modulus of 142.7 GPa, Vickers hardness of 3.757 GPa, Poisson’s ratio of 0.367, Pugh’s ratio of 3.422, Debye temperature of 377.68 K, melting temperature of 1558.07 K, vibrational energy of 8.557 x 10-2 Ry/cell, Gibbs free energy of 0.1584 Ry/cell, entropy of 7.984 x 10-4 Ry/cell/K, and specific heat at constant volume of 2.659 x 10-4 Ry/cell/K. Due to the comparable mechanical and thermal properties of CTO to Si, it can replace Si in the manufacture of MEMS. The ductile nature of CTO is ideal for manufacture of flexible MEMS such as biomedical MEMS, microbolometers, image sensors, and microbridges, which require softer and dultile substrates.
PhD Thesis
2022-01-01T00:00:00Z