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An evaluation of electronic waste management practices in the Ethekwini metropolitan area, Kwazulu-natal
Get PDFThesis (Masters: Health Sciences: Environmental Health)--Central University of TechnologyUnprecedented advancements in lifestyle and modern technology have necessitated newer and better electronic and electrical appliances. These appliances and devices have penetrated every aspect of our lives; however, not much consideration has been given to what happens to these items once it has reached its end of use or have become obsolete. Therefore, as the world moves at an ever-increasing pace towards technological advancements, there is an urgent demand to deal with increasing volumes of waste from electrical and electronic equipment (WEEE) and digital devices. Fast-changing features and the increasing availability of improved products force consumers to dispose of such devices more rapidly than ever before. When such items are discarded, they become part of the e-waste stream. This study investigated current practices in handling and disposing of e-waste and the extent to which such devices are recycled in the eThekwini Municipality area. Awareness of the need to properly dispose of such waste was assessed. To conduct this investigation, companies that provide e-waste collection services and those that recycle/discard this type of waste were identified and data were collected via selfadministered questionnaires after permission had been granted to access respondents. South African e-waste policies and legislation and eThekwini Municipality by-laws on waste management were reviewed, while academic journals, books, and magazine articles were perused for secondary data collection. The data are discussed and illuminated by various tables and graphs in this dissertation. The results indicated that 70.59% of the participating organisations had guidelines and procedures in place regarding the handling of electronic waste, but only 11.76% of these companies had a clear guideline that stated that a registered e-waste recycler should be responsible for the removal and recycling of e-waste. These recyclers should submit a disposal certificate to the client. It was found that outdated and unused equipment was used by 23.52% of the companies and that no procedural guidelines were in place to monitor disposal practices and volumes. It was found that e-waste was often stored for long periods without consideration of the possible risks this might pose. Also, 5.88% of the respondents reported that electrical and electronic equipment that was no longer functional, was crushed and disposed of at general waste landfill sites. Only 41.18% of the companies had been authorised to dispose of their e-waste. The study concludes that emerging technologies will continue to advance and create new streams of WEEE. Improved waste management strategies for this type of waste thus need to be adopted and implemented by all generators of such waste. There is also an urgent need to create awareness of the risks associated with e-waste as this will reduce mismanagement and the negative impact e-waste will have on the environment when inappropriately discarded. Education regarding e-waste disposal will also enable organisations to make informed decisions and formulate strategies to better manage such waste. A shift towards a circular economy and improved methods to manage e-waste such as the recycling of discarded e-waste to recover valuable resources is essential for the creation of a risk-free and sustainable environment
Selective laser sintering of in-situ copper-modified polyamide
No full textThesis (Master of Engineering: Mechanical Engineering)--Central University of TechnologyMetals, ceramics, glass, and polymers are materials utilized in the design and manufacture of medical devices. Due to the wide variety of features they offer, such as biocompatibility, cost effectiveness, design freedom, and balanced mechanical properties, polymer materials are increasingly used to fabricate medical device components. Selective Laser Sintering (SLS) or Laser Powder Bed Fusion (LPBF) of plastic materials is an Additive Manufacturing (AM) technique where a bed of powder polymer or elastomer is sintered by laser with the subsequent solidification of the powder layer. Polyamide-based plastic materials are utilized to produce workable AM prototypes and end-use parts. Polyamide 12 (PA12), or Nylon 12, has 12 carbon atoms with a formula [-(CH2)11C(O)NH-]n and is a thermoplastic polymer that has excellent impact strength. PA12 is less sensitive to stress cracking than other nylon polymers and has quite low moisture absorption. Copolymerisation or different fillers can modify the physical, mechanical and other properties of polyamide (PA). Microorganisms may quickly colonize various polymer surfaces, especially in-house devices. The surfaces of these devices provide the opportunity to form biofilms that can facilitate the growth of infection and fever-causing microorganisms. The growth of microorganisms can also cause staining, discolouration, odour, and reduction of performance and material properties. As the public becomes more aware of hospital-acquired antibiotic-resistant diseases, alternative antimicrobials are often used in medical devices, equipment housings, and hygienic surface coatings. Copper (Cu) is proven to be an antibacterial agent in medical devices and is nontoxic to humans in low concentrations (Cervantes and Gutierrez-Corona, 1994). The antibacterial characteristics of Cu have made it a popular choice for food and medical device surfaces that are regularly handled. One advantage of SLS is the possibility of producing in-situ sintered materials from powder mixtures. This work evaluates the characteristics of in-situ SLS copper-modified black polyamide 12 (PA12/B) samples with the addition of 10 wt.% and 20 wt.% Cu as antibacterial agent. Roughness and morphological features of manufactured SLS surfaces, porosity, conductivity, mechanical properties and antibacterial characteristics of polymer-metal composite test samples are described in detail. It was shown that polyamide-copper antibacterial composites can improve the functionality of AM parts avoiding infections in users since pure Cu possesses antibacterial capabilities
An evaluation of the emotional intelligence levels of undergraduate students at the Central University of Technology, Free State Bloemfontein campus
Get PDFThesis (Master: Somatology)--Central University of TechnologyBackground: Emotional intelligence levels could be directly linked to the academic performance and the ability of undergraduate students to manage stress. Moreover, emotional intelligence levels could be improved through psychological interventions and somatology treatments. Searching through the literature available, no studies were found on the emotional intelligence levels of undergraduate students in Central South Africa.
Problem statement: In light of the link between emotional intelligence levels, academic performance, and managing stress, a gap has been identified to study the emotional intelligence levels of undergraduate students of the Central University of Technology, Free State (CUT).
Aim: The aim of the research study was to determine the emotional intelligence levels of undergraduate students together with the relationship between emotional intelligence and demographic components, such as age, gender, and academic performance. Furthermore, to determine the relation between stress and emotional intelligence and the awareness of support services and complementary therapies available at the CUT Bloemfontein Campus.
Objectives: The research study was guided by two objectives: Firstly, a survey was conducted amongst undergraduate students at the CUT Bloemfontein Campus to assess their level of emotional intelligence. Secondly, the survey assessed the connection between emotional intelligence and demographic components, such as age, gender, and academic performance. Moreover, the connection between stress and emotional intelligence and the awareness of support services and complementary therapies on campus, and how often undergraduate students made use of these services were investigated.
Methodology: The research study made use of a descriptive research strategy based on quantitative methods that focused on the awareness of undergraduate students of emotional intelligence. The emotional intelligence level of each undergraduate student was determined by making use of the Schutte Self-Report Emotional Intelligence Test (SSEIT). A deductive approach was taken to test the existing idea that emotional intelligence could influence academic performance. The study consisted of the following three phases: Firstly, the development of a questionnaire; secondly, the distribution of the questionnaire and capturing of data; and lastly, the analysis of data, reporting results and reaching conclusions.
Results and discussion: It was established that 56% of the undergraduate students have average emotional intelligence levels. There was no significant connection between their age, or year of study, and emotional intelligence levels, although a significant association between the average academic performance and level of emotional intelligence was established. Although most of the undergraduate students were aware of services provided by the Wellness Centre (65%) and the services of a psychologist on campus (94%), merely 15% utilize these services. The knowledge and use of complementary therapies were even lower. Less than half of the undergraduate students (32%) were aware of the benefits of aromatherapy and reflexology, whereas 94% of the undergraduate students have never made use of a somatology salon and spa.
Conclusion: The outcomes of the research study shed light on the emotional intelligence levels of undergraduate students. The CUT could apply the outcomes of this study to assist their undergraduate students with improving their emotional intelligence that would in turn have a significant impact on their academic performance, due to the close relationship between emotional intelligence and academic performance. Other higher education institutions could adapt the outcomes to their specific context to assist their undergraduate students. Finally, an improved overall performance of our future leaders of the country is hoped for
Intelligent quality management system for flexible manufacturing systems
Get PDFThesis (Doctor of Engineering in Electrical Engineering)--Central University of TechnologyThe Industrial Revolution was the transition to new manufacturing processes in Great Britain, Europe and the United States. The transition included going from hand production methods to machines. The result was new chemical manufacturing and iron production processes, the increase in the use of steam power and waterpower, the development of machine tools, as well as the rise of the mechanized factory system. That was the First Revolution which began in the late 1700’s in Britain. The Second, involved the use of electric power to create mass production, beginning in the late 1800’s, in the United States. The late 1900’s gave way to the Third Industrial Revolution. During this Digital Revolution, electronics and information technology were used to automate production. The current, Fourth Industrial Revolution, is building on the Third. Industry 4.0 holds the promise of increased flexibility in manufacturing, along with mass customization, superior quality and improved productivity. Industry 4.0 has evolved from the ‘Industry 4.0’ vision, an initiative for increasing Germany's manufacturing industry competitiveness. The scope of Industry 4.0 was initially restricted to the digitalization of production processes at the factory level. Technology trends of Industry 4.0, refer to a wide variety of information, digital, operations and advanced manufacturing technologies that, collectively, push the digital industrial revolution. Intelligent manufacturing is based on the concept of optimizing manufacturing and productivity, by taking advantage of technological advances. Flexible Manufacturing Systems (FMS’s) are a form of intelligent manufacturing. A Flexible Manufacturing System reacts to changes in the production process. This includes changes in the product and the production schedule. Quality management processes should be increasingly efficient and effective, which is becoming a competitive factor for companies. Disadvantages of FMS, include its higher upfront costs and more time required to design the system specifications for a variety of future needs. Furthermore, there are costs associated with the need for specialized technicians to run, monitor and maintain the FMS. A traditional Quality Management System (QMS) cannot be used for a Flexible Manufacturing System, as it is unable to keep up with the changes in the FMS. The aim is to design, construct and evaluate an Intelligent Quality Management System (iQMS), which may learn and adapt to the change of the Flexible Manufacturing System (FMS). The emphasis of the system design is on easy initialisation, quick transition from learning to running and data handling. An initial review is carried out on the available literature on the Fourth Industrial Revolution, and flexible manufacturing systems. The application of quality management in the manufacturing industry, is investigated. The literature on flexible manufacturing is used to provide context and highlight the problem statement. A case study is used to showcase the challenges encountered, when circuit breakers of varying specifications are set up in an assembly system with interchangeable tools/stations. This highlights the assumptions that led to the formulation of the project. It provides a concise description of the study area and the methods employed. The tools used in the development of the QMS project, are discussed. The development of the Quality Management System, is discussed, detailing the hardware and software aspects of the research study. The details on the use of the ARDUINO platform to construct the QMS’s Hardware Nodes, are included in this Chapter. Furthermore, QMS Software development and deployment details are incorporated. The innovative use of QR codes to collect training data is highlighted in the Chapter. QR code decoding and training data extraction is exhibited in this section of the study. The concluding Chapter discusses the results from the iQMSs testing and data collection process, as well as observes future work. The main contributions of the study, in comparison with further available research, regarding the manufacturing industry and industry 4.0, are further highlighted. The study realised a data management system that caters to the unique data management requirements of Flexible Manufacturing Systems. A major highlight of the study shows the benefit of reworking quality management practices using new digital advances
Validation of genexpert machine using extrapulmonary samples at national tuberculosis referral laboratory in Lesotho
Get PDFThesis (Master: Health Sciences: Biomedical Technology)--Central University of TechnologyINTRODUCTION: The battle against tuberculosis (TB) is still a major public health scourge in Lesotho. Unfortunately, TB not only affects the lungs; it can also be found in other extrapulmonary areas such as the skin, brain, lymph nodes, genitourinary tract, and bones/joints. The GeneXpert is a sophisticated molecular assay that rapidly detects pulmonary TB and its resistance to rifampicin in sputum. The traditional culture TB-detection methods are still used for TB diagnosis of nonrespiratory samples. The magnitude of delayed diagnosis of extrapulmonary tuberculosis (EPTB) can be addressed if rapid and effective methods are implemented. We sought to validate the GeneXpert System using two different cartridges; Xpert Mycobacterium tuberculosis/rifampicin (MTB/RIF) and Xpert Ultra in the National Tuberculosis Reference Laboratory (NTRL) using extrapulmonary samples in this study. METHODOLOGY: This study was mainly experimental, but existing data from the NTRL database were also included. The assessment of the Xpert MTB/RIF and Xpert Ultra was comparable to culture for identifying Mycobacterium tuberculosis in extrapulmonary clinical specimens. Extrapulmonary samples from various health facilities in Lesotho were tested using the culture method (gold standard) and the GeneXpert as method to be validated. Patients from all ages and genders were included. Statistical analysis was conducted on IBM’s Statistical Package for Social Sciences (version 26). RESULTS: A total of 352 samples were analysed from 2016 to 2019. Pleural fluid was the most collected sample type (39.2%), followed by ascitic fluid (14.2%) and cerebrospinal fluid (13.6%). Of the 352 samples tested, 34 EPTB cases were detected by the GeneXpert assays and culture methods. Twenty-one cases tested positive by the GeneXpert assays alone, while only one tested positive by the culture method, and the two methods were able to both detect M. tuberculosis in 12 specimens. The sensitivity and specificity of the GeneXpert assays were 92.3% and 87.1%, respectively. Pleural EPTB was predominant in males aged 21 to 40 years. CONCLUSION: The findings from this study prove that pleural TB was the most prevalent EPTB. The outcomes of GeneXpert assays in this study do not replace culture as the gold method; however, the GeneXpert assays showed increased sensitivity and a better turn-around time of less than two hours, which can assist clinicians in making a prompt diagnosis
Optimal electrical and thermal energy management of a residential energy hub integrating renewable energy, demand response and energy storage system
Get PDFThesis (Doctor: Engineering: Electrical Engineering)--Central University of TechnologyThe energy consumption of residential buildings contributes approximately 42 % towards the total electrical energy production on a global scale. In residential buildings, the energy consumption could be further sub-categorized into the electrical energy required for space heating, space cooling and water heating, which accounts for 61.2 % of the total energy consumption, thereof. These systems utilized in large residential buildings, are vital for the occupants, to meet their thermal comfort needs, with regards to the residential building air temperature and hot water temperature. Some conventional means of performing space heating and water heating technology, is the boiler type, where hot water is transferred to the various rooms within the residential building and, thereafter, transferred to the spaces in the building, by means of a radiator. Another conventional space heating and water heating technology, is an electric element, which is used predominantly in water heating applications, as well as the wall mounted electric radiators. These conventional technologies are extremely ineffective due to their elementary operating principle. Therefore, in this study, an air-to-air heat pump was selected, to provide space heating and space cooling to the residential building and an air to water heat pump, which provides hot water to the residential building. This type of technology generally consumes approximately three times less energy, compared to the conventional technologies, whilst performing at similar levels. However, the initial investment of the air-to-air heat pump and air-to-water heat pump type technology is significantly higher in comparison and becomes economically feasible over an extended period. The air-to-air heat pump and air-to-water heat pump could be further improved through various methods, from an operational energy cost and energy efficiency perspective, such as the addition of renewable energy, energy storage systems and effective control techniques, to the residential energy hub, as well as thermal energy recovery. The residential building was integrated with renewable energy, which in this case is solar photovoltaic (PV) technology and an energy storage technology, known as hydrogen. Effective energy management techniques, making use of advanced optimization techniques, become essential when it comes to further energy efficiency optimization and operational energy cost minimization of a residential energy hub. Therefore, in this study, various methods to minimize the operational energy costs and improve the energy efficiency of the space heating, space cooling and water heating equipment are applied to a large residential building. These methods, firstly, include the addition of solar PV technology with hydrogen energy storage and, secondly, apply optimization techniques to the large residential building. The main objective is to minimize the operational energy cost of the utility grid, with respect to the Time-of-Use (TOU) tariff structure, to the electrical load and the polymer electrolyte membrane water electrolyser (PEMWE), which is responsible for producing hydrogen gas. The other main objectives, were to maximize the electrical energy supply to the load produced by the solar PV modules, optimal switching statuses of the air-to-air heat pump and the air to water heat pump. These main objectives outlined, were achieved by making use of the optimization algorithm, known as the OPTI-Toolbox, in the MATLAB software. These optimization problems are known as mixed integer nonlinear optimization problems (MINLP) and are solved using the (solving constrained integer programs) SCIP solver in the optimization toolbox of MATLAB. The first model was developed for the optimal switching control of an air-to-air heat pump space heating and space cooling system, to provide space heating and space cooling to a large residential building. A mathematical model of the proposed system was developed, after which simulations were conducted to reveal the performance, as well as the economic viability, thereof. A second model was developed, of a hydrogen PEMWE water heating system, after which the optimal control algorithm was applied and simulated. A third model was developed of the residential energy hub integrating renewable energy, demand response and energy storage system. The proposed model was simulated, in terms of its operation to evaluate the performance and the economic feasibility, thereof. Two baselines were established for the first model, to thoroughly evaluate the performance and economic feasibility of the air-to-air heat pump space heating and space cooling system. One baseline was established, for the second model, to thoroughly evaluate the performance and economic feasibility of the hydrogen PEMWE water heating system. Two baselines were established, for the third and final model, to thoroughly evaluate the performance and economic feasibility of the proposed residential energy hub integrating renewable energy, demand response and energy storage system. The proposed air-to-air heat pump space heating and space cooling system, depicted a daily operating energy cost saving of 27.63 % and 14.73 %, compared to the first and second baseline, during the selected winter day, respectively. Furthermore, a potential daily operating energy cost saving of 16.91 % and 12.30 %, could be achieved, compared to the first and second baseline, during the selected summer day, respectively. Additionally, the study focusing on the proposed hydrogen PEMWE water heating system, revealed that the hydrogen PEMWE water heating system, with optimal switching control, produced slightly less hydrogen energy and, in turn less hydrogen, compared to the standard PEMWE system. However, a daily maximum of 67.32 kWh of thermal energy was recovered during summer. Furthermore, by recovering the generated heat from the PEMWE, the time for the membrane to degrade to a thickness of 50 %, could be prolonged by 1.02 years. Thirdly and finally, the proposed large 270 occupant residential energy hub integrating renewable energy, demand response and energy storage system, revealed a potential breakeven point of 5 years, compared to the first baseline, with a potential cost-saving of 5 640 043.28 USD over a 20-year life cycle, was observed. The optimal control case revealed a potential break-even point of 5.74 years compared to the second baseline, with a potential cost-saving of 5 102 634.70 USD, over a 20-year life cycle, was observed. Furthermore, the proposed optimal control model achieved an annual operational grid energy cost-savings of 83.59 % and 82.37 %, compared to the first baseline and second baseline, respectively. The results of the various proposed models, by applying the proposed optimal control techniques, illustrated that an improved feasibility, in terms of energy efficiency and economic feasibility of high initial capital investments may be achieved. These operational energy costs and energy efficiency incentives become of great importance when it comes to the national energy grid security and greenhouse gas emissions
Optimal operation and control for a hybrid hfo-dlco gas turbine power generating plant
Get PDFThesis (Doctor: Engineering: Electrical Engineering)--Central University of TechnologyGas turbines (GT) are a critical and reliable part of modern power generation plants. They are required in aircraft engine propulsion and power generation for industrial and commercial applications where they serve as the primary mechanical power source for large pumps and compressors. These turbines typically comprise of dual nozzle gas/Heavy fuel oil – diesel light crude oil (HFO-DLCO) generators. Therefore, optimisation and control of their operation is crucial in maximising their performance and cost scaling. Significant research has been conducted, and a plethora of analytical and experimental models have been developed, to better understand that gas turbine systems exhibit nonlinear behaviour and complex dynamics. However, the requirement for accurate and reliable models of gas turbines for a variety of hybrid fuel applications, as well as for cost savings while minimising environmental impact, has been a strong incentive for researchers to continue working in this fascinating field of study. This thesis developed an intelligent control system for a hybrid dual nozzle fuel power plant to increase its energy conversion efficiency and reliability. To accomplish this, the study developed and integrated a dual nozzle power plant model and an optimal cost-effective fuel transition management into a comprehensive control system. The hybrid plant model is a novel modelling technique that combines the algorithms of PID and Model Predictive Controllers to extract plant parameters and uncertainties from operational data and to significantly improve the model's accuracy for subsequent and future analysis and research. To optimise plant efficiency, the MPC state estimator is used to generate optimal set points and PID control provides the final loop control action. By integrating heuristic MPC and PID, technologies, a nonlinear optimal control operation framework is developed. Finally, the individual control systems are integrated into a comprehensive system that manages the dual nozzle fuel GT power plant as a whole. The integrated control system enabled the power plant to operate at normal fuel switching providing a smooth wellregulated system during low fuel pressure. As a result, an intelligent autonomous control system that can perform high-quality plant-wide control is achieved, ensuring efficiency, cost-effectiveness, and reliability. As a result, the hybrid dual nozzle GT power plant achieves an intelligent autonomous control system, allowing for high-quality plant-wide fuel transition management that ensures fuel flow accuracy, efficiency, and reliability in fuel switching operation
A Pathway To Adapt Hybrid Learning For Pre-Service Teachers As The New Normal In Curriculum Practice: Using Whatsapp As A Learning Tool
Get PDFThe use of hybrid learning in curriculum practices to improve teaching and learning a recent initiatives in the package pedagogical reforms in South Africa. Nowadays, an increasing number of students have their own smartphones, and WhatsApp is becoming popular in terms of mobile learning and communication .WhatsApp is an application that can be used by students in post-secondary education to improve performance, and motivation to prepare for their learning . This article reflects on a pathway followed by pre-service economic and management sciences (EMS) teachers in their ability to adapt and sustain their learning through WhatsApp as a hybrid learning tool. The study is underpinned by connectivism theory. Qualitative research using Participatory Action Learning and Action Research (PALAR) approach as a form of critical education science is employed in research methodology and design . Semi structured Interviews were conducted with 30 Pre-Service EMS teachers to generate data. PALAR is relevant to the study as it pilgrimages three principles of responsible research innovations such as recognition of participants, establishing professional learning communities and critical reflections embracing diversity characterised in unequal education context in the South Africa. Critical discourse analysis was used to arrive at the finding that depicts close 96% of the participants are inclined to use WhatsApp as a learning tool as 84% had reliable access to Wi-Fi on campus. The paper concludes with recommendations that the hybrid learning is the future of teaching and learning in post Covid era and should be embraced
Preparation and characterisation of polylactic acid composites/nanocellulose extracted from Eucomis autumnalis for various applications
Get PDFThesis (Master Health Sciences: Environmental Health)--Central University of TechnologyPolymers produced in living cells have attracted exceptional attention due to their ecofriendliness and biodegradability. These polymers possess similar properties to
conventional plastics, making them suitable potential plastic substitutes for
sustainable development and conservation of finite oil resources. Polylactic acid (PLA)
is comparable to commonly used plastics but is inferior due to poor impact resistance,
hydrophobicity, a lack of reactive side chain groups, a slow degradation rate, and a
relatively high cost. However, PLA can benefit from the incorporation of various
polymer components with complementary properties to yield improved physical
properties. Developing fully bio-based composites of PLA and cellulose is particularly
interesting. They have mechanical and physiological properties that make them more
suitable for a wider range of applications. Herbaceous plant cell walls comprise
semicrystalline cellulose fibres embedded in a soft matrix. The crystalline part of the
inherently stiff chains extracted from plants such as E. autumnalis is subject to
research for potential roles as fillers. In this study, to fabricate a novel composite
consisting of PLA/Cellulose (stem) (PLA/Cs), three characteristically different
celluloses were extracted from various parts of E. autumnalis (bulbs, leaves, and
stem). Based on a distinguished cellulose spectrum (showing all the relevant
functional groups), increased crystallinity and thermal stability compared cellulose
from the leaves, varying contents (99.5/0.5 and 97/3.0 PLA/Cs) of a mixture of fibre
bundles and coarse aggregates of cellulose from the stems were incorporated in a
PLA matrix. The surface morphology and structural properties of the novel composites
were investigated using FTIR and SEM. In addition, the thermal and mechanical
properties of the composites were investigated using standard techniques (i.e., TGA
and Tensile). Generally, there was better distribution of Cs in PLA and improved
interfacial adhesion at high filler content (97/3.0), resulting in a high Young's modulus.
However, no significant improvement in thermal properties was observed
Complexation of syringic and ρ-coumaric acids with zinc(ii) to improve their antidiabetic efficacy
Get PDFThesis (Doctor of Health Sciences: Biomedical Technology)--Central University of TechnologyBackground: The concept of Zn(II) complexation has long been explored as a possible scientific approach to developing potential therapeutic agents for managing impaired glucose tolerance in diabetes. This has been partly due to the safety profile of zinc mineral and its functional role in insulin preservation, secretion and function. Many types of ligands have been explored as suitable ligands to develop potent antidiabetic Zn(II) complexes. However, due to the critical role of oxidative stress in the development and progression of diabetes and vascular complications, the use of polyphenols as alternative ligands for antidiabetic Zn(II) complexes has been explored by scientists. It is perceived that the antioxidant attributes of natural polyphenols may afford a Zn(II) complex an antioxidant perspective in combating diabetic oxidative stress and reducing the risk of diabetic complications. Data from some studies that have complexed zinc with dietary flavonoids support this perception to an appreciable extent. However, natural phenolic acids, which are known dietary antioxidant have been scarcely explored as antioxidant ligands for developing antidiabetic Zn(II) complexes. Therefore, in the present study, p-coumaric acid and syringic acid were used as alternative ligands to develop Zn(II) complexes, due to their promising antioxidant attributes and some other diabetes-related pharmacological attributes.
Methodology: p-Coumaric acid and syringic acid were separately complexed with ZnSO4 in a 1:2 mole ratio, respectively. The complexes were characterized by spectroscopically using FT-IR, proton NMR and high-resolution mass spectroscopy. The cytotoxic effect of the complexes was evaluated in Chang liver cells and L-6 myotubes. The antioxidant and antihyperglycaemic potential of the complex and precursors were evaluated with different experimental models. Molecular docking with target proteins linked to diabetes was performed. The antioxidant and antihyperglycaemic potential of the complexes, relative to their respective precursors were determined using in vitro, cellular and ex vivo experimental models. The complexes and their respective phenolic acids were comparatively docked against protein targets linked to diabetes. The Zn(II) complex of syringic acid was subjected to in vivo antidiabetic and antioxidant study in diabetic rats. Diabetes was induced in SD rats using 10% fructose and 40 mg/kg bw streptozotocin and thereafter subjected to a 4-week treatment with the complex and its precursors (Syringic acid and zinc sulphate) for 4 weeks at predetermined doses. Then, the effect of the treatments on diabetes and oxidative stress related parameters was measured.
Results: Spectroscopic analysis showed the complexes were formed as a double hydrate Zn(II)- biphenolate product [Zn(II)-bicoumarate.2H2O and Zn(II)-bisyringate.2H2O complexes], which each had a moiety of Zn(II) and 2 moieties of their respective phenolic acids. The in vitro radical scavenging, α-glucosidase inhibitory, antiglycation and anti-lipid peroxidative activities of the complexes were several folds stronger than their respective phenolic acids. In Chang liver cells and rat liver tissues, the complexes inhibited lipid peroxidation and GSH depletion, which was notably stronger than their respective phenolic acids and comparable to ascorbic acid. Zn(II) and the phenolic acids synergistically modulated glucose uptake in L-6 myotubes and rat muscle tissue, which may be majorly influenced by to the observed complexation-mediated increase in muscle zinc uptake. Tissue glucose uptake activity of the complexes was accompanied by increased muscle hexokinase activity, suggesting increased glucose utilization. Moreover, treatment increased muscle phospho-Akt/pan-Akt ratio, while the complexes had stronger molecular docking interaction with insulin signalling protein targets (GLUT-4, Akt/PKB, insulin receptor tyrosine kinase and IRS-1) than their respective phenolic acid precursors. The Zn(II)- bisyringate.2H2O complex was more potent than the Zn(II)-bicoumarate.2H2O, thus was subjected to in vivo antidiabetic and antioxidant study in diabetic rats. The complex improved diabetic polyphagia, polydipsia and weight loss. Complexing Zn(II) with syringic acid improved their antihyperglycaemic action by ∼28 – 36% and ∼37 - 40%, respectively, suggesting a complexationmediated synergism. This may be attributed to the observed modulatory action of the complex on insulin secretion and sensitivity, tissue glycogen production, muscle hexokinase activity and Akt phosphorylation, thus improving glucose tolerance in diabetic rats, relative to its precursors. Concomitantly, the complex reduced systemic and tissue lipid peroxidation and increased antioxidant enzymes activity in the diabetic rats, while outperforming its precursors. In some cases, the antidiabetic action of the complex was comparable to metformin. The molecular properties of the complexes (i.e., the Zn(II) and biphenolate moieties) appears to be influential in the improved bioactivities of the complexes relative to their respective precursors, suggesting a complexation mediated synergistic potential.
Conclusion: Complexing Zn(II) with these phenolic acids (p-coumaric and syringic acid) may be an underexplored therapeutic approach to improving the effectiveness of therapies for diabetes and oxidative stress management