https://ir.unisa.ac.za/handle/10500/2738 2026-09-21T13:16:17Z 2026-09-21T13:16:17Z Maziya, Lindelwa Nothando https://ir.unisa.ac.za/handle/10500/33014 2026-08-25T16:34:56Z 2026-02-27T00:00:00Z

Co-crystal engineering of N-heterocyclic active pharmaceutical ingredients with nitrobenzoic acid derivatives Maziya, Lindelwa Nothando The pharmaceutical industry continues to face challenges with properties of drugs like poor solubility, limited bioavailability and insufficient stability of active pharmaceutical ingredients (APIs), which collectively hinder drug development. Co-crystallization has been shown to be an effective strategy to improve these physicochemical properties of drugs without altering their chemical properties. In this study, fifteen novel crystalline structures were obtained using both solution-based crystallization (slow evaporation) and mechanochemistry methods. A series of N-heterocyclic APIs were co-crystallized with selected nitro-substituted aromatic co-formers, enabling the evaluation of multiple co-former families across diverse APIs. 3,5-Dinitrosalicylic acid (DNSA) formed crystalline phases with seven APIs, nitroterephthalic acid (NTPA) with six APIs, and 2-(nitrophenyl)methanol with two APIs. The crystalline structures formed included neutral co-crystals, salt co-crystals, hydrated forms and solvates, reflecting the structural diversity of outcomes possible with carefully selected co-formers and varied crystallization techniques. Notably, an unexpected esterification product was structurally identified in one of the crystalline systems, highlighting the potential for solid-state or solution-mediated transformations during crystallization. Structural characterization was performed using single-crystal X-ray diffraction, with structure solution and refinement carried out using SHELXT and SHELXL respectively. Findings on some of the crystalline structures were supported by complementary analytical techniques, including Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) spectroscopy, and Hirshfield surface analysis. Overall, the findings of this study provide valuable insight into the structural diversity in co-crystallization, supramolecular interaction driving successful co-crystallization and how different crystallization methods affect co-crystallization. Furthermore, the study introduces a series of novel co-crystals which contribute to the knowledge of pharmaceutical crystal engineering and provides a strong foundation for future research aimed at improving drug performance.

2026-02-27T00:00:00Z Papo, Tebogo Rosina Mercy https://ir.unisa.ac.za/handle/10500/32968 2026-09-20T19:02:00Z 2026-02-19T00:00:00Z

Spectroscopic screening of metabolites from the marine sponge Fibulia ramosa as a source of bioactive compounds and its anti-cancer activity Papo, Tebogo Rosina Mercy Chemical compounds categorised as natural products are diverse, with many classes such as terpenoids, steroids, alkaloids, peptides, and polyketides. Marine natural products encompass a wide array of chemical compounds found in marine organisms, including marine microorganisms, marine phytoplankton, marine algae (green, brown, and red), marine sponges, marine cnidarians, marine bryozoans, marine molluscs, marine tunicates, marine echinoderms, marine mangroves, as well as intertidal plants and intertidal microorganisms. Sponges are marine organisms that belong to the animal phylum Porifera and they comprise of four (4) main classes, even though historically only three classes of sponges were recognised, that is Calcarea (calcareous sponges); Hexactinellida (glass sponge) and Demospongiae (the demosponges, the most diverse class, including 90% of all species of sponges). The fourth class, Homoscleromorpha (the rarest and simplest class), previously grouped with the Demospongiae, is now recognised as a distinct class with approximately 117 species. Sponges comprise about 8 500 to 9 000 described living species, with approximately 150 of these sponge species found in freshwater bodies, and the vast majority being marine, inhabiting oceans, seas, or brackish water. The body of the marine sponge contains a network of pores, canals, and passageways defining them as multicellular immobile animals. In this study, the marine sponge Fibulia ramosa was investigated for its bioactive compounds, and the results are reported in this dissertation. The research tools employed in this study are MTT assays, GC-MS analysis, GC-HRTOF analysis, phytochemical screening, FT-IR, anti-cancer activity and NMR. The results have shown that Fibulia ramosa extract exhibited moderate anti-cancer activity, with selectivity indices of 4.77 (HepG2) and 5.41 (Caco-2) against normal Vero cells, indicating its potential as a moderately selective chemotherapeutic agent. While it does not meet the threshold for highly potent agents, its properties suggest that it could be used effectively in combination therapies to reduce harm to normal cells. This balance between efficacy and safety makes the extracts from Fibulia Ramosa a promising candidate for further research in targeted cancer treatments.

2026-02-19T00:00:00Z Netshithothole, Ronewa https://ir.unisa.ac.za/handle/10500/32717 2026-08-06T07:45:55Z 0024-10-09T00:00:00Z

Simultaneous Determination of Pharmaceuticals in the South African Environment Followed by the Health Risk Assessment Netshithothole, Ronewa The present work examined the occurrence of efavirenz, ibuprofen, naproxen, sulfamethoxazole, and trimethoprim in wastewater, sewage sludge, river water, estuaries, seawater, garden soil, and vegetables. This was achieved through the application of solid-phase extraction (SPE) and ultrasound-assisted solvent extraction (UASE) for sample preparation prior to liquid chromatographic analysis. The validity of these sample preparation techniques was confirmed by computing analyte recoveries after spiking the investigated matrices with mixed standards at 5 and 15 μg/L for aqueous samples and 5 and 15 ng/g for solid samples. In all cases, all the analytes were recovered within the acceptable range of 70–120%, except for sulfamethoxazole, which was recovered at 62% in wastewater influent and 56% in sludge due to the complexity of the matrices. The relative standard deviation across all the studied matrices was below 15%, indicating the precision of the analytical method. The sensitivity of the analytical method was investigated by determining method detection limits (MDL) and method quantification limits (MQL). The MDL and MQL ranged between 0.02–6.20 ng/L and 0.07–14.2 ng/L for aqueous samples and 0.08–8.36 ng/kg and 0.20–25.32 ng/kg for solid samples, respectively. The analytical method was then applied to determine the extent of pharmaceutical pollution in the aquatic environment of the Eastern Cape province. Wastewater and sewage sludge samples were highly contaminated with the targeted pharmaceuticals, with concentrations reaching 77 μg/L and 13.35 ng/g, respectively. The studied pharmaceuticals were detected in seawater samples, with ibuprofen at the highest concentration of 90 ng/L. The detected concentrations in seawater were found to pose a negligible risk to aquatic species. The studied vegetables were also contaminated, with a high detection of trimethoprim at 1501 ng/kg in spinach. In addition to the targeted pharmaceuticals, 108 other drugs were detected in the edible parts of vegetables. However, the health risks associated with the consumption of these pharmaceuticals-contaminated vegetables were found to be negligible. The overall findings of the present study provided invaluable insights into pharmaceutical pollution across various environmental matrices. The results highlighted the critical need to improve the maintenance and efficiency of wastewater treatment plants as they are major contributors to pharmaceutical pollution. Continuous disposal of pharmaceuticals into the environment could lead to increased concentrations, deteriorating the quality of freshwater, and promoting the emergence of antimicrobial resistance.

0024-10-09T00:00:00Z Kgwadibane, Tshupo https://ir.unisa.ac.za/handle/10500/32566 2026-06-29T16:49:15Z 2025-12-05T00:00:00Z

Nickel-manganese phosphate/electrochemical exfoliated graphene nanocomposites for hybrid supercapacitors Kgwadibane, Tshupo The global shift toward sustainable energy technologies has increased the demand for advanced energy storage systems that deliver both high energy and power densities. Conventional supercapacitors provide excellent power output, rapid charge-discharge capability, and superior cycling stability; however, their low energy density restricts practical applications. In contrast, rechargeable batteries offer higher energy densities but are limited by slower charge rates and reduced cycling stability. Hybrid configurations that integrate the complementary advantages of both systems have therefore emerged as a promising approach to achieving balanced performance. Nickel-manganese phosphate/electrochemically exfoliated graphene NiMn(PO4)2/EEG) nanocomposite was synthesized via a hydrothermal method. Structural and morphological analyses, including X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), high-resolution scanning electron microscopy (HRSEM), Fourier-transform infrared spectroscopy (FTIR), and Raman spectroscopy, confirmed the formation of well well-crystallised composite with homogeneous morphology. The NiMn(PO4)2/EEG composite leverages the multiple redox-active sites and structural robustness of bimetallic phosphate combined with the high conductivity of electrochemically exfoliated graphene, resulting in enhanced charge transport efficiency and electrochemical performance. Additionally, this work presents an investigation of heteroatom-doped EEG thin film synthesised via a two-step process involving graphite intercalation and electrochemically exfoliation in sulphuric-phosphoric acid medium, enabling in-situ doping with nitrogen (N), phosphorus (P), and sulphur (S). The exfoliation products were vacuum filtered to form porous films. Raman spectroscopy revealed Fermi-level shifts of approximately 0.5 eV and heterogeneous defect distributions. The doped EEG films exhibited enhanced electrical conductivity (~10,000 S·m-1) and improved interfacial properties, as evidenced by reduced adhesion forces in force-distance measurements. Electrochemical analyses demonstrated that Fermi-level modulation facilitated rapid interfacial charge transfer by lowering the electrode-electrolyte potential barrier. The doped EEG films achieved a specific capacitance of 150.5 F·g-1 at 1.0 A·g-1, confirming their potential as highly conductive supports for hybrid electrode configurations. Furthermore, a NiMn(PO4)2/EEG composite was integrated with activated carbon (AC) derived from wastewater sludge to fabricate energy storage devices. The NiMn(PO4)2/EEG composite was synthesised hydrothermally, while AC was produced via phosphoric acid activation. Characterisation verified the formation of a mixed-metal phosphate phase anchored on few-layer graphene. The optimised NiMn(PO4)2/50 mg EEG electrode achieved a high specific capacity of 822.1 C·g-1 at 1 A·g-1, significantly outperforming pristine NiMn(PO4)2. In an asymmetric configuration (NiMn(PO4)2/EEG//AC), the device delivered an energy density of 40.0 Wh·kg-1, a peak power density of 6538 W·kg-1, and retained 87% of its capacitance after 5000 cycles at 5 A·g-1. These results underscore the synergistic contribution of EEG towards improved electrical conductivity and redox kinetics, while demonstrating the potential of wastewater sludge-derived AC for sustainable electrode development. Overall, this research integrates synthesis, characterisation, and electrochemical evaluation to elucidate the role of heteroatom-doped EEG in enhancing the electrochemical behaviour of NiMn(PO4)2-based electrodes. By uniquely combining NiMn(PO4)2, heteroatom-doped graphene, and waste-derived activated carbon, this study presents an innovative, sustainability-oriented approach to device design. These findings contribute to the advancement of scalable, sustainable energy storage technologies.

2025-12-05T00:00:00Z