47 research outputs found
Essential Oil Characterization and Biological Activities of Millettia thonningii (Schumach. & Thonn.) Baker Leaf, Stem and Root
No full textMillettia thonningii has been used in folk medicine for centuries to treat pains, pathogenic diseases, and radical-induced aliments. Essential oils (EOs) are a source of bioactive compounds, and their potential application as an alternative to synthetic products in the treatment of infectious diseases and oxidative stress has been validated. Leaf, stem and root EOs of M. thonningii were obtained by hydro-distillation and characterized by Gas Chromatography-Mass Spectrometry (GC-MS) technique. Antioxidant activity was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical while antibacterial activity was assessed using agar well diffusion and broth micro-dilution techniques. EOs yields obtained were 0.18, 0.20 and 0.27% for the leaf, stem and root, respectively. Seventeen (leaf), twenty-two (stem) and fifteen (root) compounds were identified in EOs representing 96.3, 98.2 and 91.0% of the whole composition, respectively. Two major constituents in leaf essential oil (EO) were β-atlantol (23.6%) and β-caryophyllene (22.7%); β-caryophyllene (54.3%) was the most abundant in stem EO followed by caryophyllene oxide (11.4%) and α-humulene (7.2%) while epicedrol (57.1%) was the major compound in the EO followed by cedrol (10.6%) and β-cedrene (9.8%). α-Humulene, caryophyllene oxide, cedrol and isolongifolen-9-one were common in the three parts. Stem EO showed the highest antioxidant activity among others (IC50 = 259.76 μL/mL). However, the leaf, stem and root EO showed strong inhibition on the growth of Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi and Streptococcus pneumoniae (14.0 - 20.0 mm and 5 - 20 μL/mL). This research further justified the ethnomedicinal uses of M. thonningii against pathogenic disorders and radical-induced aliments
(R. Br. ex Oliv.)
No full textEssential oils (EOs) from Ochna afzelii leaves, stems and roots were extracted and characterised by hydrodistillation and Gas Chromatogragphy-Mass Spectrometry (GC/MS) techniques, respectively. Antioxidant activity was evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH*) method while antibacterial activity was determined using agar well diffusion and broth microdilution methods. Leaf, stem, and root oils afforded thirteen, ten and seven compounds, respectively, which were characterized by a high percentage of oxygenated sesquiterpenes and sesquiterpene hydrocarbons. The major compound in O. afzelii leaf and root EOs was & beta;-Atlantol, while the O. afzelii stem EO had (E)-& beta;-ionone as its major compound. The leaf oil displayed highest antioxidant activity (IC50 = 238.14 & mu;L/mL). All the EOs showed antibacterial activities against Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, and Streptococcus pneumoniae, with the zones of inhibition and MIC values ranging from 12.0-18.0 mm and 2.5-10 & mu;L/mL, respectively. O. afzelii has a mild antioxidant effect, but can be a potential source of natural antibacterial agents
Synthesis and biolgical screening of potential plasmodium falciparum DXR inhibitors
Get PDFThe non-mevalonate isoprenoid pathway, also known as the 1-deoxy-D-xylulose-5- phosphate DXP pathway, is absent in humans, but present in the anopheles mosquito responsible for the transmission of malaria. DXP reductoisomerase - a key enzyme in the DXP pathway in Plasmodium falciparum (PfDXR) has been identified as a target for the design of novel anti-malarial drugs. Fosmidomycin and its acetyl analogue (FR900098) are known to be inhibitors of PfDXR and, in this study, synthetic variations of the fosmidomycin scaffold have led to four series of novel analogues. Particular attention has been centred on the introduction of various substituted benzyl groups in each of these series in order to occupy a recently discovered vacant pocket in the PfDXR active-site and thus enhance ligand-enzyme binding. In the process 160 ligands and precursors have been prepared, no less than 119 of them novel. Fistly, a series of C-benzylated phosphonate esters and phosphonic acids were synthesised, in which the fosmidomycin hydroxamate Mg2+- coordinating moiety was replaced by an amide funtionality and the number of methylene groups in the “hydrophobic patch” between the phosphonate and the hydroxamate moiety was decreased from two to one. Several approaches were explored for this series, the most successful involving reaction of 3- substituted anilines with a-bromo propanoic acid in the presence of the coupling agent 1,1'- carbonyldiimidazole (CDI), followed by Michaelis-Arbuzov phosphonation using triethyl phosphite. Reaction of the resulting chiral phosphonate esters with bromotrimethylsilane gave the corresponding phosphonic acids in good yields. In order to obviate chirality issues, a second series of potential “reverse” fosmidomycin analogues was synthesised by replacing the methylene group adjacent to the the phosphonate moiety with a nitrogen atom. Deprotonation, alkylation and phosphorylation of various amines gave diethyl #-benzylphosphoramidate ester intermediate. Aza-Michael addition of these intermediates, followed by hydrolysis gave the corresponding carboxylic acids which could be reacted with different hydroxylamine hydrochloride derivatives to afford the novel hydroxamic acid derivatives in good yields. Thirdly, a series of a novel #-benzylated phosphoramidate derivatives were prepared as aza- FR900098 analogues. Alkylation of different amines using bromoacetalde-hyde diethylacetal gave a series of N-benzyl-2,2-diethoxyethylamine compounds, which were then elaborated via a futher six steps to afford novel #-benzylated phosphoramidate derivatives. Finally, in order to ensure syn-orientation of the donor atoms in the Mg - coordinating group and, at the same time, introduce conformational constraints in the ligand, the hydrophobic patch and the hydroxamate moiety were replaced by cyclic systems. Several approaches towards the synthesis of such conformationally constrained phosphoramidate analogues from maleic anhydride led to the unexpected isolation of an unprecedented acyclic furfuryl compound, and 1H NMR and DFT-level theoretical studies have been initiated to explore the reaction sequence. A series of #-benzylated phosphoramidate derivatives containing dihydroxy aromatic rings (as the conformationally constrained groups) to replace the hydroxamate moiety, were successfully obtained in six steps from the starting material, 3,4-dihydroxylbenzaldehyde. While in vitro assays have been conducted on all of the synthesised compounds, and some of the ligands show promising anti-malarial inhibitory activity - most especially the conformationally constrained cyclic #-benzylated phosphoramidate series. Interestingly, a number of these compounds has also shown activity against T.brucei - the causative agent of sleeping sickness. In silico docking studies of selected compounds has revealed the capacity of some of the ligands to bind effectively in the PfDXR active-site with the newly introduced benzyl group occupying the adjacent vacant pocket. The physico-chemical properties of these ligands were also explored in order to predict the oral-bioavailability. Most of the ligands obeyed the Lipinski rule of 5, while QSAR methods have been used in an attempt to correlate structural variations and calculated molecular properties with the bioassay data.Thesis (PhD) -- Faculty of Science, Chemistry, 201
Studies towards the development of novel antimalarial agents
Get PDFConsiderable efforts have been made in the modification of existing antimalarial drugs, and the support of incentive programmes have led to a drastic decrease in malaria cases reported by WHO during the past 6 years. However, the development of drug resistance threatens the eradication of this deadly disease and has prompted research on the synthesis of novel antimalarial drugs. Our research has involved the design and synthesis of novel benzylated phosphonate esters as potential 1-deoxy-D-xylose-5-phosphate reductoisomerase (DXR) inhibitors. A series of amidoalkylphosphonate esters were obtained by reacting various 3-subsituted anilines and heterocyclic amines with chloroalkanoyl chlorides and reacting the resulting chloroalkanamides with triethyl phosphite using Michaelis-Arbuzov methodology. Benzylation of the phosphonate esters afforded a series of novel N-benzylated derivatives in good yields and these compounds were fully characterised by NMR and HRMS methods. Several approaches to the introduction of a benzyl group at the C-2 position of the phosphonate ester derivatives have been explored, leading unexpectedly to the isolation of unprecedented tetrahydrofuranyl derivatives. Studies towards the preparation of potential bi-functional PfDXR / HIV-1 RT inhibitors have also been initiated. Preliminary in silico docking studies of selected non-benzylated and benzylated phosphonated derivatives into the Pf-DXR active-site has provided useful insight into the binding potential of these ligands. Bioassays have revealed a very low toxicity for all the synthesised phosphonated compounds and a number of these ligands also exhibit a promising inhibitory activity against the Plasmodium parasite
Evaluation of Concentration of some Heavy Metals in Water, Soil, and Fish from Ponds in Lugbe, Idu and Kuje in the Federal Capital Territory (FCT), Abuja, Nigeria.
No full textElectronic Human Resource Management (e-HRM) and Organisational Performance
No full textThis study was caried out to examine employees’ perception of the effect of electronic human resource management (e-HRM) on organizational performance. Focused on four e-HRM components: e-recruitment, e-training, e-performance system, e-compensation combined effect on organizational performance (financial, customers, internal business, learning/growth) and determined the component with the strongest effect. Questionnaire survey covering demographics, e-HRM components and organizational performance on 332 respondents drawn from middle to senior level management employees of two Brewery firms in South-West Nigeria. Questions were framed to assess the extent to which they agree or disagree with the use and effect of e-HRM on organizational performance. Data collected was analysed using inferential statistical techniques of Partial Least Squares-Structural Equation Modelling to test the significance of e-HRM on organizational performance. Respondents perceived e-HRM improved organizational performance. Model β = 0.690, t = 17.491, f 2 =0.910, predicted that P ˂ 0.05 up to 48% variation in organisational performance is explained by e-HRM practices. Weight of each component showed: e-Recruitment= 0.383, e-Training= 0.078, e-Performance System= 0.216, e-Compensation= 0.250 as e-recruitment is perceived to have the strongest weight and effect on organizational performance. Implication is that the organisations should strengthen e-Recruitment exercise and strategically position e-HRM practices as corporate strategies to enhance organization performance
Bacteriological examination of normal upper respiratory tract of puppies with particular ref1erence to staphylococci
Get PDFThe nasal bacterial flora of 60 apparently normal puppies were examined, with special reference to Staphylococcus species. A total of 106 bacterial isolates were encountered, out of which the coagulase-negative Staphylococcus epidermidis was the most common microbe (58.5%). Other bacteria encountered were Staphylococcus intermedius and Bacillus species with an incidence of 9.4%, respectively. Corynebacteriun xerosis showed an incidence of 4.7%, while the lowest incidence of 2.8% was recorded for Escherichia coli. The incidence of Staphylococcus intermedius recorded in this study is of public health importance because the nasal carriage has been implicated as an important factor in introducing Staphylococcus species onto sites of skin of humans and dogs. Hence, there is an urgent need to educate pet owners on the zoonotic potentials of staphylococcal organisms. The need for regular check-ups cannot be overemphasized
A study of the stylistic markers of the language of cartoons in Nigeria
No full textThis paper discusses the stylistic characteristics of the language of cartoons in some Nigerian newspapers. The analysis focuses on printing styles, stylistic registers, and textual features. The author concludes that the informal style (exemplified by the occurrence of Pidgin English, colloquial forms, loan blends, ellipsis, and telegraphic sentences) characterizes the language of the cartoons. Thus, cartoonists use language as an artistic medium in which various options of language are explored for effective communication
Relationship Between Work Ethics and Senior Non-Teaching Staff’s Productivity in South-South Universities in Nigeria
Get PDFThis study examined the relationship between work ethics and senior non-teaching staff productivity in universities in South-South, Nigeria. Three research questions were raised and one was hypothesized to guide the study. [1]The descriptive survey correlational research design was adopted for the study. The target population of the study comprised 9,508 out of which Nine hundred and twenty-three (923) senior non-teaching staff were selected across south-south universities in Nigeria. The multistage and proportional-to-size sampling techniques were used in obtaining the sample size. The research instruments were questionnaires, titled, Work Ethics Questionnaire and Productivity Rating Scale. The reliability of the Work Ethics Questionnaire was 0.695 using Pearson (r). The Cronbach alpha, reliability of the Productivity Rating Scale was 0.734 at 0.05 level of coefficient. Mean rating and standard deviation were applied to answer research questions while the Pearson Product Moment Correlation Coefficient was used to test the hypothesis formulated. Findings from the study revealed that the level of compliance of senior non-teaching staff with work ethics in South-South Universities in Nigeria was low. There was a significant relationship between work ethics and senior non-teaching staff productivity in south-south Universities in Nigeria. The study therefore recommended that senior non-teaching staff in South-South, Nigeria, improve their compliance with work ethics to increase their productivity within the University syste
Regularized Deep Neural Network for Post-Authorship Attribution
No full textA thesis submitted to the Faculty of Science, in fulfillment of the requirements for the degree of Doctor of Philosophy in Computer Science, School of Science, University of the Witwatersrand, Johannesburg, 2024Post-authorship attribution is the computational process of determining the legitimate author of an online text snippet, such as an email, blog, forum post, or chat log, by employing stylometric features. The process consists of analysing various linguistic and writing patterns, such as vocabulary, sentence structure, punctuation usage, and even the use of specific words or phrases. By comparing these features to a known set of writing pieces from potential authors, investigators can make educated hypotheses about the true authorship of a text snippet. Additionally, post-authorship attribution has applications in fields like forensic linguistics and cybersecurity, where determining the source of a text can be crucial for investigations or identifying potential threats. Furthermore, in a verification procedure to proactively uncover misogynistic, misandrist, xenophobic, and abusive posts on the internet or social networks, finding a suitable text representation to adequately symbolise and capture an author’s distinctive writing from a computational linguistics perspective is typically known as a stylometric analysis. Additionally, most of the posts on social media or online are generally rife with ambiguous terminologies that could potentially compromise and influence the precision of the early proposed authorship attribution model. The majority of extracted stylistic elements in words are idioms, onomatopoeias, homophones, phonemes, synonyms, acronyms, anaphora, and polysemy, which are fundamentally difficult to interpret by most existing natural language processing (NLP) systems. These difficulties make it difficult to correctly identify the true author of a given text. Therefore, further advancements in NLP systems are necessary to effectively handle these complex linguistic elements and improve the accuracy of authorship attribution models.
In this thesis, we introduce a regularised deep neural network (RDNN) model to solve the challenges that come with figuring out who wrote what after the fact. The proposed method utilises a convolutional neural network, a bidirectional long short-term memory encoder, and a distributed highway network to effectively address the post-authorship attribution problem. The neural network was utilised to generate lexical stylometric features, which were then fed into the bidirectional encoder to produce a syntactic feature vector representation. The feature vector was then fed into the distributed high-speed networks for regularisation to reduce network generalisation errors. The regularised feature vector was then given to the bidirectional decoder to learn the author’s writing style. The feature classification layer is made up of a fully connected network and a SoftMax function for prediction. The RDNN method outperformed the existing state-of-the-art methods in terms of accuracy, precision, and recall on the majority of the benchmark datasets. These results highlight the potential of the proposed method to significantly improve classification performance in various domains. Again, the introduction of an interactive system to visualise the performance of the proposed method would further enhance its usability and effectiveness in quantifying the contribution of the author’s writing characteristics in both online text snippets and literary documents. It is useful in processing the evidence that is needed to support claims or draw conclusions about the author’s writing style or intent during the pre-trial investigation by the law enforcement agent in the court of law. The incorporation of this method into the pretrial stage greatly
strengthens the credibility and validity of the findings presented in court and has the potential to revolutionise the field of authorship attribution and enhance the accuracy of forensic investigations. Furthermore, it ensures a fair and just legal process for all parties involved by providing concrete evidence to support or challenge claims.
We are also aware of the limitations of the proposed methods and recognise the need for additional research to overcome these constraints and improve the overall reliability and applicability of post-authorship attribution of online text snippets and literary documents for forensic investigations. Even though the proposed methods have revealed some unusual differences in author writing style, such as how influential writers, regular people, and suspected authors use language, the evidence from the results with the features extracted from the texts has shown promise for identifying authorship patterns and aiding in forensic analyses. However, much work remains to be done to validate the methodologies’ usefulness and dependability as effective authorship attribution procedures. Further research is needed to determine the extent to which external factors, such as the context in which the text was written or the author’s emotional state, may impact the identified authorship patterns. Additionally, it is crucial to establish a comprehensive dataset that includes a diverse range of authors and writing styles to ensure the generalizability of the findings and enhance the reliability of forensic analyses.
Furthermore, the dataset used in this thesis does not include a diverse variety of authors and writing styles, such as impostors attempting to impersonate another author, which limits the generalizability of the conclusions and undermines the credibility of forensic analysis. More studies can be conducted to broaden the proposed strategy for detecting and distinguishing impostors’ writing styles from those of authentic authors when committing crimes on both online and literary documents. It is conceivable for numerous criminals to collaborate to perpetrate a crime, which could aid in improving the proposed methods for detecting the
existence of multiple impostors or the contribution of each criminal writing style based on the person or individual they are attempting to mimic. The likelihood of numerous offenders working together complicates the investigation and necessitates advanced procedures for identifying their individual contributions, as well as both authentic and manufactured impostor contents within the text. This is especially difficult on social media, where fake accounts and anonymous profiles can make it difficult to determine the true identity of those involved, which can come from a variety of sources, including text, WhatsApps, chat images, videos, and
so on, and can lead to the spread of misinformation and manipulation. As a result, promoting a hybrid approach that goes beyond text as evidence could help address some of the concerns raised above. For example, integrating audio and visual data may provide a more complete perspective of the scenario. As a result, such an approach exacerbates the restrictions indicated in the distribution of data and may necessitate more storage and analytical resources. However, it can also lead to a more accurate and nuanced analysis of the situationMM202
