Research Articles (Chemistry)

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This collection contains some of the full text peer-reviewed/ refereed articles published by researchers from the Department of Chemistry

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Parametric study on APTES silanization of coal fly ash for enhanced rubber composite performance
Moyo, Dennis Simbarashe; Kleinhans, George; Wi, Xueting; Doucet, Frédéric J.; Van der Merwe, Elizabet Margaretha (MDPI, 2025-11-14)
The surface modification of coal fly ash (CFA) with silane coupling agents improves its compatibility with polymer matrices and supports its use as a sustainable filler in composite materials. This study examined the effects of the solvent system, reaction temperature, and pH on the grafting of 3-aminopropyltriethoxysilane (APTES) onto CFA surfaces. Functionalization was assessed by Fourier-transform infrared spectroscopy (FTIR), focusing on the CH2 symmetric and asymmetric stretching bands of pure APTES at 2919 and 2957 cm−1, noting that a slight shift in these bands can be expected following the change in the local chemical environment upon grafting. Solvent mixtures containing water (ethanol/water, acetone/water, and sulfuric acid/water) produced stronger coupling than the toluene solvent, which indicated the importance of water for APTES hydrolysis and silanol formation. Coupling efficiency increased with temperature and reached a maximum at 80 °C, where the balance between hydrolysis and condensation favored the formation of stable Si–O–Si bonds. The highest degree of functionalization was observed at pH 9, which corresponds to the point of zero charge of alumina in CFA, where neutral surface hydroxyl groups were available to react with silanols. These results define the optimal conditions for APTES grafting onto CFA and demonstrate its potential as a silane-modified filler in polymer composites. Atomic force microscopy (AFM) provided direct visual evidence of significant surface texture modifications induced by APTES treatment in the ethanol/water solvent system.
Interfacial s-scheme charge transfer in MgIn2S4/ZnO heterojunction for enhanced photodegradation of tetracycline and efficient water splitting
Yusuf, Tunde Lewis; Olatunde, Olalekan C.; Masekela, Daniel; Saliu, Oluwaseyi D.; Modibane, Kwena Desmond; Onwudiwe, Damian C. (Royal Society of Chemistry, 2025-08)
Environmental pollution and high energy costs are among today's most pressing global challenges. Photocatalysis offers a cost-effective and environmentally sustainable strategy to address these issues by enabling efficient pollutant degradation and hydrogen production. This work constructed a nanoflower MgIn2S4 and nanorod ZnO heterojunction to enhance photocatalytic performance through an interfacial S-scheme charge transfer mechanism. Unlike most reported ZnO-based heterojunctions in the literature, this approach introduces MgIn2S4, a ternary sulfide with a narrow band gap and a high conduction band potential, to form a heterostructure material with a strong redox potential and efficient charge separation. The MgIn2S4/ZnO heterojunction exhibited superior photocatalytic activity, achieving a remarkable 94% tetracycline (TCE) degradation efficiency, 1.4 and 3.9 times higher than that of pristine MgIn2S4 and ZnO, respectively. Furthermore, the heterojunction demonstrated an improved hydrogen evolution rate of 8.29 mmol h−1 g−1, significantly surpassing ZnO (6.96 mmol h−1 g−1) and MgIn2S4 (6.24 mmol h−1 g−1). The enhanced performance is attributed to the efficient interfacial charge transfer, as confirmed by X-ray photoelectron spectroscopy (XPS) analysis and electrochemical characterization, demonstrating charge migration from MgIn2S4 to ZnO. Mechanistic investigations further revealed that the S-scheme charge transfer mechanism effectively promoted charge separation and facilitated the generation of reactive radical species, ultimately leading to improved photocatalytic activity. This study highlights the potential of the rationally designed MgIn2S4/ZnO S-scheme heterojunction as a highly efficient and sustainable photocatalyst for organic pollutant degradation and hydrogen production under visible light irradiation, providing a promising solution to environmental and energy challenges.
Microstructural, morphological, and optical properties of Fe2O3 nanoparticles obtained from Fe-MIM MOF
Olatunde, Olalekan C.; Ravele, Murendeni P.; Yusuf, Tunde Lewis; Onwudiwe, Damian C. (IOP Publishing, 2025-03)
This study explores the microstructural, morphological, and optical properties of Fe2O3 nanoparticles synthesized from the pyrolysis of ZIF-8 like Fe-2-methyl imidazole (MIM) metal–organic frameworks (MOFs). Using X-ray diffraction (XRD) profile analysis methods, including the modified Scherrer, Williamson–Hall (W-H), size strain plot, and Halder-Wagner methods, the impact of annealing temperature on the microstructural parameters and crystal defects of the obtained Fe2O3 nanoparticles was investigated. The nanoparticles exhibited high crystallinity and a rhombohedral α-Fe2O3 phase. Morphological analysis through transmission electron microscopy (TEM) revealed distinct structural features, while UV–vis spectroscopy was employed to examine their optical properties. The results indicated that higher annealing temperatures enhance crystallinity, reduce defect density, and improve atomic mobility. This comprehensive analysis provides valuable insights into the synthesis-structure–property relationships of Fe2O3 nanoparticles, highlighting their potential applications in applications such as gas sensing and photocatalysis.
The common concept of anticooperativity among molecules is fundamentally flawed, based on novel and unified molecular-wide and electron density (MOWeD) concept of chemical bonding
Cukrowski, Ignacy; Zaaiman, Stéfan; Hussain, Shahnawaz (MDPI, 2025-04-27)
A non-linear (non-additive) increase in stability of hexamers follows an increase in the total number of (i) aad (a double proton acceptor) plus add (a double proton donor) waters commonly linked with anticooperativity and (ii) the total number of intermolecularly delocalized electrons (intermolNdeloc) in the 3D space occupied by a hexamer. Subsequently, we obtained nearly a perfect linear correlation between increase in the cluster stability and intermolNdeloc. Individual water molecules that act as either aad or add (i) delocalize the largest number of electrons throughout a cluster; (ii) are involved in the strongest attractive, hence energy-stabilizing intermolecular interaction with the remaining five waters; (iii) have the most significant quantum component of the intermolecular interaction energy and (iv) relative to six non-interacting water molecules, stabilize a hexamer the most, as quantified by a purposely derived mol-FAMSEC energy term. Clearly, the all-body approach used in the unified, molecular-wide and electron density (MOWeD)-based concept of chemical bonding contradicts the commonly accepted view that aad and add water molecules are involved in anticooperativity in 3D water hexamers. Consequently, we propose here a general definition of cooperativity that should be applicable to any n-membered molecular cluster, namely the quantifiable, classical physics- and quantum-based cooperativity phenomenon is synonymous with the intermolecular all-body delocalization of electrons, leading to the increase in stability of individual molecules on an n-membered cluster formation.
Production of in situ mixed gas phase volatile organic compound standards for sorbent tube applications
Leakwe, Ntoko Moses; Welthagen, Werner; Forbes, Patricia B.C. (Elsevier, 2025-12)
Volatile organic compounds (VOCs) are a significant class of air pollutants, as they pose a risk to human health and the environment. Precise quantification of VOCs sampled onto sorbent tubes requires gas phase standards at suitable concentrations. Herein, we present a: - gas standard preparation method for benzene, toluene, ethylbenzene and xylene (BTEX) prepared from liquid standards by means of evaporation and dynamic dilution with nitrogen- demonstration of the applicability of the LiqMix Cascade gas mix system. Repeatability and reproducibility were first successfully demonstrated via direct GC–MS analysis of generated gas mixtures. Then µg levels of generated gas standards were adsorbed onto sorbent tubes employed in active sampling and ng levels were collected onto Radiello cartridges used in passive sampling, followed by liquid extraction or thermal desorption and GC–MS analysis. Accuracy was verified by a BTEX certified reference material (99 % recovery). The LiqMix Cascade gas mix system was shown to produce precise and repeatable concentrations of BTEX gas phase standards for sorbent tube sampling applications for the first time.
Efficient recovery of platinum and palladium by fixed‑bed column adsorption using acylthiourea‑ and amine‑modified silica
Mphahlele, Malehlogonolo R.R.; Mosai, Alseno Kagiso; Tutu, Hlanganani; Kotzé, Izak A. (Springer, 2025-12)
The rising demand and limited natural reserves of platinum group metals (PGMs) have intensified the need for sustainable recovery from secondary sources. This study investigates the continuous fixed-bed column adsorption of platinum (Pt) and palladium (Pd) from aqueous solutions using silica-anchored acylthiourea and amine-modified adsorbents. Adsorption experiments were performed at pH 2 and a flow rate of 2.00 mL/min, with variations in bed height and metal concentration to optimise recovery. Among the four adsorbents tested, DTMSP-BT-SG exhibited the highest adsorption capacities, with Thomas model-derived values reaching 470.67 mg/g for Pt and 382.19 mg/g for Pd. Increasing bed height and metal concentration enhanced both breakthrough capacity and the volume of solution treated, with up to 4775 bed volumes processed. Comparison with batch-mode adsorption revealed that, although equilibrium was achieved more rapidly in batch systems, column mode enabled significantly higher treatment volumes and yielded higher capacities. Breakthrough data were best described by the Thomas and Yoon–Nelson models (R2 > 0.90), while the Bohart–Adams model was less predictive across the full breakthrough profile. The findings confirm the superior performance of acylthiourea-based adsorbents, particularly DTMSP-BT-SG, in large-scale continuous recovery of Pt and Pd from industrial and mining wastewater.
Facile synthesis of iron-based MIL-101 metal-organic framework as a potential hydrogen storage material
Mosupi, Keaoleboga; Ndamyabera, Christophe Adrien; Masukume, Mike; Musyoka, Nicholas M.; Langmi, Henrietta Wakuna (Springer, 2026-03)
Conventional approaches for metal-organic framework synthesis have shortcomings that may be circumvented through unconventional approaches, which offer fast reactions and scale-up opportunities. This work reports the successful preparation of iron-based MIL-101 utilizing unconventional precursors: iron extracted from acid mine water and terephthalic acid derived from waste polyethylene terephthalate. Three methods were employed including conventional solvothermal, unconventional microwave-assisted and unconventional sonochemical-assisted synthesis and the resulting Fe-MIL-101 was evaluated as an adsorbent for hydrogen. Unconventional synthesis drastically reduced synthesis duration from 20 h (solvothermal) to 4 h (sonochemical-assisted) and 2 h (microwave-assisted). The prepared materials displayed comparable surface areas, with the sample from microwave-assisted synthesis exhibiting a surface area of 512 m2 g− 1 while that from sonochemical and conventional solvothermal methods exhibited surface areas of 702 and 717 m2 g− 1, respectively. Correspondingly, the highest hydrogen uptake (1.03 wt% at 1 bar, 77 K) was attained for the solvothermal Fe-MIL-101. The feasibility of synthesizing Fe-MIL-101 holistically from these specific waste sources using unconventional methods, with an advantage of shortened reaction times, has been proven in this study.
Synthesis, characterization, anti-nematicidal, and computational study of Copper(II) complex derived from fluoro-substituted Schiff base ligand
Lawan, Salisu Y.; Ndahi, Naomi P.; Galadima, Ibrahim B.; Wahab, Olaide O.; Yusuf, Tunde Lewis; Coetzee, Louis-Charl C.; Abd El-Maksoud, Mostafa S.; Waziri, Ibrahim (Wiley, 2025-06)
In this study, a novel fluoro-substituted Schiff base ligand (HL) was synthesized through a condensation reaction between 2-bromo-4-(trifluoromethoxy)aniline and 2-hydroxybenzaldehyde in methanol solvent at room temperature. The ligand was subsequently reacted with copper(II) acetate to produce the corresponding Cu(II) complex (CuL2). Both the ligand and its complex underwent characterization using various techniques including nuclear magnetic resonance, ultraviolet-visible, Fourier-transform infrared, thermogravimetric analysis, elemental analysis, and mass spectroscopy. In addition, the solid-state structure of the complex was determined through single crystal X-ray diffraction analysis, confirming the successful isolation of the compounds. Subsequently, the nematicidal activities of the ligand and its complex were assessed through in vitro egg hatching inhibition and mortality rate assays, in comparison to the control, carbofuran (Crf), at concentrations of 50 and 100 µM over a 24–72-h period. The results indicated the ligand's superiority over the complex in both assays at lower concentrations. At a concentration of 50 µM, the ligand HL demonstrated 100% egg-hatching inhibition at 24, 48, and 72 h, whereas the complex CuL2 showed egg-hatching inhibition rates of 93.86 ± 0.22%, 98.76 ± 0.14%, and 99.33 ± 0.52% at the same time intervals. The control, Crf, exhibited inhibition rates of 56.33 ± 0.33%, 69.94 ± 0.6%, and 67.00 ± 0.34% over the same time period. Similarly, at a concentration of 100 µM, both the ligand and complex demonstrated 100% egg-hatching inhibition at 24, 48, and 72 h, while the control showed egg-hatching rates of 88.16 ± 0.84%, 89.9 ± 0.55%, and 90.8 ± 0.50%. Regarding the mortality rate, at 50 and 100 µM, the ligand HL exhibited a 100% mortality rate within 24 to 72 h, whereas the complex CuL2 displayed mortality rates of 56.66 ± 0.33%, 63.3 ± 0.23%, and 86.66 ± 0.13% at 24, 48, and 72 h, respectively, with a mortality rate of 100% at 100 µM within the same time intervals. The control, Crf, demonstrated mortality rates of 54%–67% at 50 µM and 62%–78% at 100 µM within 24–72 h. Additionally, the density-functional theory study revealed the electronic properties of the compounds, reinforcing the experimental findings.
Determination of South African carbon dioxide emission factors for selected solid fuels
Kornelius, Gerrit; Forbes, Patricia B.C.; Garland, Rebecca M. (Academy of Science of South Africa, 2026-03-26)
South Africa’s National Climate Change Response Policy requires accurate reporting of greenhouse gas (GHG) emissions. To achieve this, the South African Department of Forestry, Fisheries and the Environment initiated a process to develop country-specific emission factors (referred to as Tier 2 factors by the Intergovernmental Panel on Climate Change (IPCC)) for fuels produced or used locally, which are more accurate than those currently used (Tier 1). In this work, we report on the development of such county-specific emission factors for the solid fuels most commonly produced and used in South Africa, based on the analysis of 107 samples. The samples received were classified into types based on the IPCC fuel classification method, which has some differences from that used in South Africa. The CO2 emission factor for sub-bituminous coal, mainly used for power generation and in the liquid fuels/chemical sectors of South Africa, was found to be 97 807 kg CO2/TJ. For ‘other bituminous coal’, the CO2 emission factor was found to be 101 171 kg CO2/TJ. These emission factors are higher than the IPCC default (also referred to as Tier 1) factors, which have been in use in South Africa to date. As solid fossil fuel use is a major contributor to South Africa’s GHG emissions, this implies higher than previously estimated CO2 emissions from this sector as well as a higher contribution to global emissions. SIGNIFICANCE: • South African Tier 2 carbon dioxide emission factors for solid fuel use are reported for the first time, as required by South Africa’s commitments under the United Nations Framework Convention on Climate Change and the Paris Climate Agreement. • The Tier 2 carbon dioxide emission factors were derived from the analysis of over 100 South African solid fuel samples. • Emission factors for the fuels used in the largest amounts are higher than the default Tier 1 factors previously used, leading to an increase in reported emissions for a similar fuel use. • The main user of coal in South Africa, the power generation sector, uses sub-bituminous coal based on the IPCC classification system, which includes volatile matter as a classification criterion. • Using the same IPCC criteria, the majority of samples from other South African industrial and commercial users are classified as ‘other bituminous coal’.
Computational and molecular dynamics insights into the antithrombotic mechanism of triterpenes derived from Melaleuca bracteata var. Revolution Gold (Myrtaceae)
Appiah-Kubi, Patrick; Osunsanmi, Foluso Oluwagbemiga; Opoku, Andrew Rowland; Singh, Ashona (MDPI, 2026)
BACKGROUND/OBJECTIVES : Thrombin, a serine protease central to coagulation and platelet activation, remains an important target for the development of safer and more effective antithrombotic agents. Naturally derived pentacyclic triterpenoids, such as betulinic acid and its acetylated derivatives, 3β-acetoxybetulinic acid, exhibit promising antiplatelet aggregation activity in validated in vitro and ex vivo assays; however, the molecular determinants underlying their direct thrombin inhibition remain unexplored. RESULTS : Docking and MM/GBSA analyses revealed that Baa exhibits the strongest binding affinity (ΔG = −29.58 ± 2.97 kcal/mol), exceeding those of Ba (−20.94 ± 5.81 kcal/mol) and Asp (−18.87 ± 4.18 kcal/mol). Baa forms a highly persistent hydrogen bond with Trp96 (95.5% occupancy) and extensive hydrophobic contacts with Trp215, Leu99, Ile174, and Tyr60A residues defining thrombin’s aryl-binding pocket. MD trajectories demonstrated that Baa binding reduced solvent-accessible surface area (SASA) and residue fluctuations, indicating enhanced structural compaction and stability. In contrast, Ba exhibited weaker, transient hydrogen bonding, while Asp bound primarily near the catalytic triad. The triterpenes exhibit limited oral bioavailability, free PAINS alerts, favourable permeability and metabolic stability. CONCLUSIONS : Acetylation at C-3 (acetoxy substitution) substantially enhances thrombin binding via cooperative hydrogen bonding and van der Waals stabilisation, explaining the superior experimental inhibitory potency of Baa. These findings provide a mechanistic framework for structure-guided optimisation of triterpenoid-based thrombin inhibitors and support their further experimental development. Methods: In this study, molecular docking, molecular dynamics (MD) simulations (400 ns), and MM/GBSA free energy analyses were employed to elucidate the binding mechanisms of 3β-acetoxybetulinic acid (Baa), betulinic acid (Ba), and aspirin (Asp) within the thrombin receptor active site. The simulations were explicitly grounded in previously reported chromogenic antithrombin assays and platelet aggregation studies and were designed to mechanistically rationalise the experimentally observed inhibitory potency.
Advances in solid handling for continuous flow synthesis of specialty chemicals and pharmaceuticals
Johnston, Zen; Peme, Thabo; Mabasa, Tommy; Len, Christophe; Riley, Darren Lyall; Panayides, Jenny-Lee; Sagandira, Cloudius Ray (Nature Research, 2026-02)
Continuous flow chemistry has transformed the synthesis of pharmaceuticals and specialty chemicals by advancing sustainability, efficiency, and process control. Despite these advantages, the management of solids remains a major challenge, often leading to clogging, inefficient mixing, and limitations in scalability. This review discusses recent strategies developed to overcome these obstacles, including the use of continuous stirred-tank reactors, packed-bed reactors with immobilized reagents, reaction design modifications, Pickering emulsions, colloidal nanoparticle suspensions, and specialised equipment such as agitated tubular reactors, spinning disk reactors, and sonicated systems. By critically assessing these developments, we chart the trajectory toward more resilient and robust flow-based manufacturing, consolidating continuous flow chemistry as a cornerstone of modern chemical manufacturing.
Phytogenic TiO2-biochar nanocomposite derived from Prunus dulcis for enhanced Rhodamine B removal from aqueous systems
Amaku, James Friday; Omobhude, Ifeoma Anne; Amadi, Okoche Kelvin; Yusuf, Tunde Lewis; Mtunzi, Fanyana M.; Greener, Jesse (Taylor and Francis, 2026)
Please read abstract in the article.
Catha edulis and Datura stramonium mitigate oxidative stress, mitochondrial dysfunction, and cell death in an SH-SY5Y model of Parkinson's disease
Mogale, Tidimalo; De Beer, Andries Daniël; Rudolph, Willem Johannes; Steenkamp, Vanessa (Elsevier, 2026-04-06)
INTRODUCTION : Parkinson's disease (PD), the second most common neurological disorder, is often managed with medications targeting specific symptoms. Complementing conventional therapies, medicinal plants are frequently used for neurological disorders, including PD. This study evaluated the effects of crude extracts and fractions of Catha edulis (Vahl) Forssk. ex Endl. and Datura stramonium L.—psychoactive plants—on PD-related mechanisms using SH-SY5Y human neuroblastoma cells. METHOD : Crude extracts of C. edulis (leaves) and D. stramonium (leaf/root mixture) were prepared using dichloromethane/methanol (50/50). Fractionation was performed via C8 solid-phase extraction. Cytotoxicity and cytoprotective effects of the crude extracts and fractions against 6-hydroxydopamine-induced cytotoxicity were assessed using the sulforhodamine B assay. Mechanistic studies included reactive oxygen species (ROS) generation, mitochondrial integrity, and apoptosis assays. In silico analysis was used to assess the binding of biomarkers to dopamine receptors. RESULTS : Both plant extracts exhibited minimal cytotoxicity. Crude extracts and fractions (F1–F7) displayed cytoprotective effects (5.8–34.28 %). The highest ROS reduction was observed for F1 of C. edulis (1.72-fold) and F2 of D. stramonium (1.33-fold). Both extracts reduced caspase 3/7 activation and maintained mitochondrial integrity. Atropine and scopolamine showed cytoprotection with IC50 values of 49.48 μM and 48.26 μM, respectively. In silico analysis indicated strong binding affinities of norephedrine and noradrenaline to dopamine D1 and D2 receptors. CONCLUSION : Both plant extracts preserved cell viability, reduced ROS levels, and maintained mitochondrial integrity, highlighting their potential as therapeutic agents for PD.
Synthesis of MIL-53(Al) metal-organic framework from aluminium-lined multi-layered packaging materials and polyethylene terephthalate bottles
Dlamini, Nokubongwa Xol’sile; Ndamyabera, Christophe Adrien; Masukume, Mike; Musyoka, Nicholas M.; Langmi, Henrietta Wakuna (Springer, 2026)
A promising approach towards the synthesis of metal-organic frameworks (MOFs) is the use of precursors that can be extracted from waste materials found in landfills. In this work, we explore a combination of two waste materials for Al-based MOF synthesis. Aluminium sulphate was successfully derived from Poly-Al pellets obtained from multi-layered packaging materials. Terephthalic acid (BDC) was obtained from polyethylene terephthalate (PET) waste bottles. Both precursors were employed as metal and organic linker sources, respectively to synthesise MIL-53(Al). The results are compared with those of corresponding MOFs synthesised from commercial precursors and partly waste precursors. The study revealed that the structural properties of MIL-53(Al) synthesised from the two waste materials are comparable to those obtained when the MOF is synthesised using commercial sources of precursors or partly waste precursors. The MOFs were highly crystalline and stable up to 500°C. An improvement was observed in the surface area of the MOF when synthesised from complete waste (1588 m2/g) as opposed to partly waste (1323 and 1197 m2/g) and commercial precursors (1468 m2/g). Although hydrogen adsorption capacity of the synthesised MOF materials was low at low pressures (< 0.5 wt% at 1 bar and 77 K), attributable to the narrow pore form of MIL-53(Al), this work demonstrates an approach to waste management while producing high-value materials for various applications.
Synthesis, antimicrobial evaluation, and in silico studies of some novel hydrazinylquinoline and pyrazoline derivatives as potential antimicrobial agents
Bako, Rabiu; October, Natasha; Idris, Abdullahi Yunusa; Hamza, Asma’u Nasir; Adeshina, Gbonjubola Olusesi; Rufa’i, Ahmed; Muhammad, Isah Jamiu; Yakubu, Yahaya (SpringerOpen, 2025-09-25)
Antimicrobial resistance remains a major global public health challenge, contributing to increased mortality rate and treatment failures in an effort to address this growing challenge, the present research work focused on the synthesis and evaluation of new hydrazone scaffold and pyrazoline derivatives (coded HS6–HS10) as potential antimicrobial agents. The target compounds were synthesized via one-pot condensation reactions and characterized using FTIR, 1H, and 13C NMR techniques. Their antimicrobial activities were assessed in vitro against a panel of Gram-positive, Gram-negative bacteria, and fungal strains. However, their assessment revealed broad spectrum of antimicrobial activity, where the compounds bearing biaryl-substituted hydrazones with electron-donating or electron-withdrawing groups at para- and or meta-positions showed highest potency. However, MIC values of 12.5 mg/mL were observed against clinical isolates such as E. coli, S. typhi, and P. aeruginosa, while S. aureus, B. subtilis, and S. pneumoniae were inhibited at 12.5–25 mg/mL, while MIC values of 50 mg/mL were recorded against Aspergillus niger, indicating weak antifungal activity. The molecular docking studies conducted using target microbial enzymes such as dihydrofolate reductase (DHFR) and squalene epoxidase (SQLE) against the ligands HS7 and HS8 have strong binding affinities towards DHFR (− 9.6 and − 9.4 kcal/mol) and SQLE (− 9.8 and − 10.2 kcal/mol), respectively, outperforming standard reference drugs ciprofloxacin (− 7.4 kcal/mol) and terbinafine (− 9.8 kcal/mol). Meanwhile, the in silico ADME analysis confirmed that all compounds satisfied Lipinski’s rule of five, suggesting favourable drug-like properties. In conclusion, these findings suggest that substituted hydrazone and pyrazoline derivatives possess considerable promising scaffolds for developing better novel antimicrobial agents that are capable of combating resistant pathogens.
A bibliometric review of research on climate change in Africa
Ilo, Obianuju Patience; Emmanuel, Stephen Sunday; Adesibikan, Ademidun Adeola; Ore, Odunayo T.; Bayode, Ajibola A.; Badamasi, Hamza; Sanni, Saheed O.; Simatele, Mulala D. (Elsevier, 2025-12)
The increasing frequency and severity of climate change-related disasters have made it a dominant issue in global public policy debates. In Africa, scholarly climate change research publications have gradually evolved, reflecting growing academic engagement with the continent’s unique climate challenges. This study makes a novel contribution by conducting a bibliometric analysis that not only maps the volume of scholarly output but also explores key trends, geographic distribution, keywords, leading researchers, collaboration networks, and research visibility. Using the VOSviewer visualisation tool, network maps were generated from a dataset of 662 research publications. The findings indicate that scholarly interest in this area gained momentum around 2016 and has continued to grow, with South Africa, Nigeria, and Ghana emerging as leading contributors. However, the analysis also highlights limited collaboration among authors and institutions, which may impede the coherence and impact of climate-related policy and practice. Moreover, the study identifies a disconnect between the production of climate knowledge and its practical application. To address this gap, the paper recommends that climate scientists reassess their approaches to collaboration and strengthen partnerships with media professionals to enhance the dissemination of accurate and actionable climate information.
Occurrence, concentration, and risk assessment of selected pharmaceuticals in representative cropland soils and their underlying groundwater in Gauteng province, South Africa
Ngoetjana, Matome Peter; Tesfamariam, Eyob Habte; Brown, Sally; Wooding, Madelien; Dippenaar, Matthys Alois (Springer, 2025-08)
Traceable levels of pharmaceuticals are frequently detected in various environmental matrices. However, studies investigating the occurrence of pharmaceuticals in cropland soils and underlying groundwaters are relatively limited, hindering risk assessments. This study aims the following: (1) determine the occurrence of selected pharmaceuticals in cropland soils and underlying groundwater, (2) investigate the correlations between pharmaceutical’s occurrence in cropland soils and underlying groundwater, (3) evaluate the correlations between soil and water parameters and pharmaceutical’s concentration, and (4) estimate human health risk from pharmaceuticals present in groundwater. A single soil and groundwater sampling campaign was conducted across eighteen farmers’ fields, characterized by varying farm management practices. Caffeine, carbamazepine-10,11-epoxide, carbamazepine diol, and N4-acetylsulfamethoxazole were detected in groundwater, with concentrations reaching 67.1, 106.7, 506.7, and 113.8 ng L−1, respectively. Three of these compounds, carbamazepine-10,11-epoxide, carbamazepine diol, and N4-acetylsulfamethoxazole, were also present in soils with concentrations reaching 10.0, 353.5, and 59.1 ng g−1 dry weight, respectively, indicating potential soil-to-groundwater transfer. Principal component analysis revealed a strong correlation between the application of commercial inorganic fertilizers and carbamazepine-10,11-epoxide levels and the irrigation practices and the levels of caffeine, carbamazepine diol, and N4-acetylsulfamethoxazole in the soil and groundwater. Risk quotients showed that caffeine poses negligible risk to human health through drinking water exposure. Overall, the findings suggest that pharmaceuticals are present in South African croplands and underlying groundwater, though current levels do not pose a significant risk to human health. However, future studies should focus on other metabolites of pharmaceuticals due to their higher concentrations in the soil and groundwater.
Bioprospecting heavy-metal rhizospheres for novel therapeutics against high-priority multi-drug-resistant Pseudomonas aeruginosa and Acinetobacter baumannii : a case of toxic to treatment
Millard, Kylah B.; Onuofin, John O.; Invernizzi, Luke; Daramola, Michael Olawale; Iwarere, Samuel Ayodele (Wiley, 2025-09)
This study investigated the antimicrobial potential of rhizospheric microbiota isolated from heavy-metal-contaminated soils against two extremely drug-resistant (XDR) pathogens, Pseudomonas aeruginosa (strain ATCC 27853) and Acinetobacter baumannii (strain ATCC-BAA-1605). Heavy-metal-contaminated rhizospheres were sequentially exposed to ex-situ and in vitro enrichment with heavy metals from battery waste and incubated for 168 h. The surviving microbiota were screened against P. aeruginosa and A. baumannii, and crude extracts of high-performing strains were tested against the pathogens using agar well diffusion assays. The novelty and components of the extracted secondary metabolites from environmentally stressed rhizospheric microorganisms were inferred using ultra-performance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS). Results indicated that these secretions inhibited the growth of XDR pathogens (approximately 3.0 × 108 CFU/mL), forming inhibition zones of up to 50 mm. Furthermore, the pathogens were more responsive to exudates from microbiota in environmentally stressed rhizospheres compared to those from organic rhizospheres (control). Heavy-metal-stressed microbiota secrete metabolites that show superior antimicrobial activity and successfully inhibit the growth of XDR pathogens. The UPLC-HRMS analysis indicated the tentative characterisation of the metabolites, particularly Tolyposamine and Gentiatibetine, by the evaluated microbiota, suggesting their relevance as biopharmaceuticals, and could lead to future antibiotic production.
Efficient photocatalytic degradation of metoprolol using activated carbon supported NiFe-layered double hydroxides (NiFe-LDH/C) under solar-driven simulation
Biata, Raphael N.; Mabhulusa, Wendy; Mofokeng, Lethula E.; Ratshiedana, Rudzani; Munonde, Tshimangadzo S.; Nxumalo, Edward N. (KeAi Communications Co., 2025-09)
The efficient photocatalytic degradation of pharmaceuticals in wastewater is critically important for environmental protection. The synthesis and characterization of NiFe-LDH/C for the photocatalytic degradation of selected β-blockers, specifically metoprolol, under UV light conditions were investigated in this study. The study aimed to explore the potential of NiFe-LDH/C as a catalyst for the degradation of metoprolol, a commonly used pharmaceutical compound in the treatment of chronic diseases such as high blood pressure and chest pains, which is frequently detected in wastewater. The selection of NiFe-LDH/C was driven by the need for materials with high photocatalytic activity, the ability to generate reactive oxygen species and enhance charge separation, and stability under solar light. Activated carbon was employed as a support to increase the surface area and improve the dispersion of the LDH particles, thereby enhancing overall photocatalytic efficiency. The results showed that NiFe-LDH/C exhibited excellent photocatalytic activity in degrading metoprolol under both UV and sunlight-mediated conditions, with degradation efficiencies of over 89 %. Furthermore, the characterization of the NiFe-LDH/C catalyst revealed its stability and recyclability, making it a promising candidate for the efficient removal of pharmaceutical compounds from wastewater through photocatalytic degradation. The characterization results showed that the NiFe-LDH/C exhibited a high degree of crystallinity and a well-defined layered structure. The photocatalytic experiments demonstrated that the NiFe-LDH/C was effective in degrading metoprolol and ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) was used to elucidate the degradation products of metoprolol in water.
Chlorinated paraffins in global air : first results from the GAPS and GAPS-megacities networks
Saini, Amandeep; Kutarna, Selene; Niu, Shan; Mohindra, Meera; Schuster, Jasmin K.; Mastin, Jacob; Eng, Anita; Harner, Tom; Yates, Alan; Sweetman, Andrew J.; Jiménez, Begoña; Manzano, Carlos A.; Gaga, Eftade O.; Stevenson, Gavin; Alharbi, Hattan A.; Falandysz, Jerzy; Lee, Ji Eun; Miglioranza, Karina S.B.; Tominaga, Maria; Jariyasopit, Narumol; Rojas, Néstor Y.; Amador-Muñoz, Omar; Forbes, Patricia B.C.; Alani, Rose; Iyer, Suresh Ramasubramanya; Lee, Seung Bok; Nishino, Takahiro; Shoeib, Tamer; Jans, Urs; Qiu, Xinghua; Cheng, Zhen (American Chemical Society, 2026-02-13)
This study presents the first global data set of measured chlorinated paraffins (CPs), including short-chain (SCCPs), medium-chain (MCCPs), and long-chain chlorinated paraffins (LCCPs) in ambient air, derived from a single coordinated sampling network, i.e., the Global Atmospheric Passive Sampling (GAPS) network, using a passive sampling approach. Concentrations exhibited pronounced regional disparities, with the combined levels in two megacities─Lagos, Nigeria (512,000 pg/m3) and Beijing, China (258,000 pg/m3) exceeding by more than 1.5-fold the combined total levels observed across the rest of the world (∼459,000 pg/m3). Evidence of long-range atmospheric transport was observed at remote sites in western Canada (Little Fox Lake and Whistler), influenced by trans-Pacific air trajectories during the sampling period. These findings underscore the substantial global heterogeneity in the spatial distribution of CPs and the heavily disproportionate contributions of a few regions. Notably, the major producers/emitters, such as China, had several years of delay in ratifying the SCCP listing under the Stockholm Convention (Annex A, elimination since 2017 for congeners with > 48% chlorine content), and some countries have yet to ratify. Without the timely implementation of regulatory measures in these jurisdictions, global concentrations are expected to remain stagnant or even increase if emissions persist at current levels. These results further suggest that substantial time lags are likely before measurable declines in SCCP concentrations, and potentially in recently listed MCCPs, are observed even in regions where control measures are already in place. Hence, this global data set serves as a baseline for future assessments of temporal and spatial trends.

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