Research Articles (Chemistry)

Permanent URI for this collectionhttp://hdl.handle.net/2263/1724

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

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Now showing 1 - 20 of 639

Antimalarial potential, LC-MS secondary metabolite profiling and computational studies of Zingiber officinale
(Taylor and Francis, 2024) Faloye, Kolade O.; Tripathi, Manish K.; Adesida, Stephen A.; Oguntimehin, Samuel A.; Oyetunde, Yemisi M.; Adewole, Adetola Henry; Ogunlowo, Ifeoluwa I.; Idowu, Esther A.; Olayemi, Uduak I.; Dosumu, Olamide D.
Malaria is among the top-ranked parasitic diseases that pose a threat to the existence of the human race. This study evaluated the antimalarial effect of the rhizome of Zingiber officinale in infected mice, performed secondary metabolite profiling and detailed computational antimalarial evaluation through molecular docking, molecular dynamics (MD) simulation and density functional theory methods. The antimalarial potential of Z. officinale was performed using the in vivo chemosuppressive model; secondary metabolite profiling was carried out using liquid chromatography–mass spectrometry (LC–MS). Molecular docking was performed with Autodock Vina while the MD simulation was performed with Schrodinger desmond suite for 100 ns and DFT calculations with B3LYP (6-31G) basis set. The extract showed 64% parasitaemia suppression, with a dose-dependent increase in activity up to 200 mg/kg. The chemical profiling of the extract tentatively identified eight phytochemicals. The molecular docking studies with plasmepsin II and Plasmodium falciparum dihydrofolate reductase-thymidylate synthase (PfDHFR-TS) identified gingerenone A as the hit molecule, and MMGBSA values corroborate the binding energies obtained. The electronic parameters of gingerenone A revealed its significant antimalarial potential. The antimalarial activity elicited by the extract of Z. officinale and the bioactive chemical constituent supports its usage in ethnomedicine.
In vitro nitric oxide inhibition of selected south African medicinal plants : a bio-guided purification of anti-inflammatory compounds from Conyza scabrida
(Elsevier, 2025-07) Rali, Sibusiso; Mshengu, Bongiwe P.; Van De Venter, Maryna; Maharaj, Vinesh J.
This study aimed to investigate the anti-inflammatory activity of plant species by in vitro screening of extracts, fractions, and pure compounds on LPS-activated RAW 246.7 mouse macrophages. Plants were sourced from the plant repository in the Biodiscovery Centre, at the University of Pretoria. The plant materials were ground into fine powdered and extracted with dichloromethane: methanol (DCM:MeOH) (1:1) followed by 100 % MeOH, filtered, concentrated, and dried to generate extracts. Twelve extracts were fractionated using positive pressure solid phase extraction (ppSPE) Gilson liquid hander workstation, resulting in seven fractions per plant extract. The observed anti-inflammatory activity was mainly attributed to specific ppSPE fractions of the plant extracts rather than the entire crude extract.The most active plants species identified with 90 % inhibition at 25 μg/mL, were Dodonaea. viscosa, Buxus natalensis, Flacourtia. indica, and Conyza scabrida. The crude extract and ppSPE fractions (6 and 7) of C. scabrida demonstrated strong anti-inflammatory activity at 50 μg/mL with 97.8 % and 97.0 % inhibition, respectively. The Ultra-Performance Liquid Chromatography coupled with Quadrupole Time-of-Flight Mass Spectrometry Mass Spectrometry (UPLC-QTOF-MS) analysis of the active ppSPE fractions was used to tentatively identify two major compounds 5,3′,4′-trihydroxy-3,6,7,8-tetramethoxyflavone (C1) and hautriwaic acid (C2) and were subsequently purified using preparative high-performance liquid chromatography (prep-HPLC-MS) and confirmed by Nuclear Magnetic Resonance (NMR). At a concentration of 100 μM, they inhibited NO production by 96.6 % and 59.2 %, respectively. We have provided scientific preliminary evidence supporting ethnopharmacological claims of twelve South African medicinal plant species traditionally used to treat inflammatory diseases.
Characterization of selected solid fuels and their calorific values in Kenya : a case Study of Bomet, Narok, Taita-Taveta, and Mombasa counties
(Springer, 2024-04) Bosire, Josephate O.; Osano, Aloys M.; Oyaro, Nathan; Maghanga, Justin K.; Forbes, Patricia B.C.
Energy for household use is expensive and is thus less available to communities, especially in developing countries. In Kenyan rural households, the primary source of domestic cooking fuel is either locally available firewood, charcoal produced through gradual pyrolysis of these firewood, or biomass briquettes. Nonetheless, there have been minimal investigations that characterize and compare typical firewood species and the associated charcoal fuels in terms of moisture content, calorific values, and their relationships. Consequently, this study sought to ascertain the moisture content, ultimate analysis, and calorific values of Grevillea robusta, Arundinaria alpina, Eucalyptus globulus, Azadirachta indica, Gliricidia sepium, Adansonia digitata L., Cyprus, and Acacia auriculiformis wood fuels, and the corresponding charcoal and briquettes in Bomet, Narok, Taita Taveta, and Mombasa Counties. The bomb calorimeter method was used to determine the calorific values while the elemental analyzer was used to determine carbon, nitrogen, sulfur, and oxygen levels in the fuel. Moisture content of the wood fuels ranged from 2.36 ± 0.01% to 4.93 ± 0.02%, briquettes from 2.57 ± 0.02–3.22 ± 0.07%, and charcoal, from 2.02 ± 0.01–2.73 ± 0.05%. Briquette samples had the highest carbon composition of 74.69% and 75.77%, followed by charcoal and firewood, respectively. It was found that firewood fuels had a higher oxygen content (39.47–49.96%) than the other fuels (21.71–36.54%). In elemental analysis, the majority of the samples had sulfur and nitrogen content of less than 1% while the hydrogen content ranged from 1.26% to 6.04%. The calorific values of the solid fuels ranged between 13.13 ± 0.11 MJ/kg and 32.71 ± 0.19 MJ/kg. The findings suggest a relationship between moisture content and calorific values since low moisture content fuels had high calorific values which could be attributed to the increased value of the carbon-to-oxygen (C/O) proportion (ranging from 0.94 to 3.36). Based on the calorific value analysis, the order of fuel strength was found to be; charcoal > firewood > briquettes. As a result, the study's findings demonstrate that the proximate, ultimate, and calorific values analyses of solid fuel play a vital role in determining the best fuel with higher energy values in accordance with the International Energy Agency's (IEA) requirements.
Preliminary mechanistic insights into the detection of ethanol vapour using MnO2 NRs-CNPs-poly-4-(vinylpyridine) based solid-state sensor operating at room temperature
(Elsevier, 2025-01) Malepe, Lesego; Ndinteh, Derek Tantoh; Ndungu, Patrick Gathura; Mamo, Messai Adenew
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Fabrication of BiVO4/Ag2CrO4 heterojunction composites modified with graphene oxide for enhanced photoelectrochemical and photocatalytic performance
(Royal Society of Chemistry, 2024-11) Oluwole, Adewunmi Olufemi; Yusuf, Tunde Lewis; Tichapondwa, Shepherd Masimba; Daramola, Michael Olawale; Iwarere, Samuel Ayodele; samuel.iwarere@up.ac.za
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Exploring anticancer activity and DNA binding of metal (II) salicylaldehyde Schiff base complexes : a convergence of experimental and computational perspectives
(Wiley, 2025-05) Waziri, Ibrahim; Sookai, Sheldon; Yusuf, Tunde Lewis; Olofinsan, Kolawole A.; Muller, Alfred J.
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Quorum sensing inhibition by South African medicinal plants species : an in vitro and an untargeted metabolomics study
(BioMed Central, 2025-04) Moyo, Phanankosi; Bodede, Olusola; Wooding, Madelien; Famuyide, Ibukun Michael; Makhubu, Fikile Nelly; Khorommbi, Ndivhuwo Kevin; Ofori, Michael; Danquah, Cynthia A.; McGaw, Lyndy Joy; Maharaj, Vinesh J.
BACKGROUND : The emergence of antimicrobial resistance (AMR) is imperiling global health, hence, the need to remedy this challenge by discovering new therapeutic strategies and agents. Quorum sensing inhibition (QSI) is opined as a potential novel strategic approach in the fight against AMR by abrogation of bacterial virulence and pathogenicity. Currently, there are no clinically approved QSI drugs. Based on this, this study evaluated the QSI properties of South African plant species. METHODS : Twenty-nine extracts and their corresponding 203 fractions generated using solid phase extraction were screened for QSI activity in vitro against Chromobacterium violaceum ATCC 12472. Active and inactive fractions of the most potent plant species were analysed using UPLC-HRMS. The acquired mass spectral data was subjected to chemometric analysis. RESULTS : From the QSI assays, three plant species showed remarkable QSI activity, measured by dose-dependent inhibition of violacein production (IVP), at sublethal concentrations. Terminalia phanerophlebia emerged as the most active species, with the extract and five of its fractions showing good activity in IVP (IVP IC50 ≤ 0.1 mg/mL). This was closely followed by Momordica cardiospermoides whose crude extract and two of its corresponding fractions showed good activity (IVP IC50 ≤ 0.1 mg/mL). Three fractions of Helichrysum odoratissimum also had good activity (IVP IC50 ≤ 0.1 mg/mL) marking it one of the most potent selected species. Chemometric analysis identified five compounds including olivetol and hydroxytyrosol as chemical markers positively associated with the QSI activity of T. phanerophlebia. CONCLUSION : In conclusion, the findings of our study provided insight into the QSI properties of South African plant species. Further studies will focus on the isolation of the putative active compounds and the in vitro evaluation of their QSI activity.
Larvicidal and antiplasmodial studies of Eucalyptus camaldulensis (Myrtaceae) leaf
(Springer, 2024-12) Adesida, Stephen A.; Oguntimehin, Samuel A.; Famuyiwa, Funmilayo G.; Faloye, Kolade O.; Ogundele, Seun B.; Bello, Oyenike I.; Oladiran, Oluyemi J.; Olusola, Ayobami J.; Adewole, Adetola Henry; Adebayo, Praise A.; Oredola, Maryam O.
Eucalyptus camaldulensis is a medicinal plant used as insect repellant and antimalarial agent in ethnomedicine. This study examined the antiplasmodial and larvicidal potential of E. camaldulensis leaf extract and also identified the plant extract's most active fraction(s). The acute oral toxicity test of the methanol extract was evaluated using Lorke’s method. The larvicidal assay was performed on the extract and partitioned fractions according to the 2005 World Health Organization guidelines, while the 4-day chemosuppressive and curative antimalarial assays were carried out against Plasmodium bergei bergei. Endosulphan and chloroquine (10 mg/kg) was used as the positive controls for the larvicidal and antiplasmodial assays, respectively, while tween 80 in normal saline (1%) was the negative control. The methanol leaf extract of EC showed good larvicidal activity across all tested concentrations (LC50 3.79 ± 0.64 mg/mL), while the aqueous fraction with LC50 of 2.80 ± 0.14 mg/mL was the most active. Its acute toxicity test showed it was safe up to 5000 mg/kg. The extract significantly increased dose-dependent antiplasmodial activity for the chemosuppressive and curative models (p < 0.05) than the negative control. At 800 mg/kg, EC gave chemosuppressive (53.69 ± 1.62%) and curative (81.26 ± 1.87%) activities, which was significantly lower than that of 10 mg/kg chloroquine (82.00 ± 0.57% and 92.51 ± 0.22% respectively). The aqueous partitioned fraction gave the highest chemosuppression (73.84 ± 2.73%) at 80 mg/kg, which was comparable to the positive control. The methanol extract of E. camaldulensis leaf is a promising larvicidal and antimalarial agent that could proffer a solution to vector control and the prevalence of malaria.
A conceptual framework for costing perovskite solar cells through material flow cost accounting
(MDPI, 2025-04) Van der Poll, Hendrik Johannes; Van der Poll, Huibrecht Margaretha; Van der Poll, John Andrew; hendrik.vanderpoll@up.ac.za
There is a global demand for alternative energy sources away from unsustainable fossil fuels. The Conference of Parties (COP) 26 agreed that fossil fuels should be phased down; at COP27, anxiety about the cost and availability of energy was raised, and COP28 reiterated the phasedown of coal power. Solar technology in the form of perovskite solar cells is one such alternative energy source. This article considers the fabrication of the perovskite layer in a solar cell and postulates the extent to which material flow cost accounting (MFCA) could be used as a feasible costing method, among other things, to address material flows and waste reduction. Through MFCA, the monetary and physical flows of materials are identified and can be applied throughout the supply chain to facilitate affordability, from the extraction of the ore to the transportation and fabrication of the chemicals, manufacturing and distribution of the solar cell and panels, and, finally, the recycling of the panel. Informed by these observations, a conceptual framework for applying MFCA in fabricating the perovskite layer in the supply chain is developed based on sets of qualitative propositions. Future work will involve researching the processes involved in manufacturing solar cells, costing raw materials, energy flows, and solar cell manufacturing emissions.
A comparative study of sol-gel synthesized ZnO/GO and ZnO/g-C3N4 nanocomposites in the photocatalytic degradation of acetaminophen
(Wiley, 2025-02) Chebwogen, Judith; Nyongesa, Francis W.; Mwabora, Julius M.; Ntshani, Gershom M.; Ndungu, Patrick Gathura; patrick.ndungu@up.ac.za
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Justicidin B and related lignans from two South African Monsonia species with potent activity against HeLa cervical cancer cells
(Elsevier, 2024-04) Tajuddeen, Nasir; Muyisa, Séverin; Maneenet, Juthamart; Nguyen, Hung Hong; Naidoo-Maharaj, Dashnie; Maharaj, Vinesh J.; Awale, Suresh; Bringmann, Gerhard
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Recent advances in Fe-based metal-organic frameworks : structural features, synthetic strategies and applications
(Elsevier, 2025-04) Mosupi, Keaoleboga; Masukume, Mike; Weng, Guoming; Musyoka, Nicholas M.; Langmi, Henrietta Wakuna; henrietta.Langmi@up.ac.za
Metal organic frameworks (MOFs) are very exciting porous materials owing to their unique properties such as high surface areas, high pore volume, tunable functionalities and great thermal stabilities. The properties of MOFs can be diversely constructed by precise control of synthesis conditions. Amongst the thousands of MOFs that have been discovered to date, Fe-MOFs make up a percentage of these MOFs. Fe-MOFs are increasingly gaining great interest due to their unique properties and chemical versatility. However, comprehensive reviews on their emerging architectural features and designs as well as strategies for tailoring their applications. Therefore, in this review, we present a panoptic summary of the recent developments of Fe-MOFs, which includes synthetic strategies, activation methods, functionalization, overview of selected applications, current challenges impeding their commercialization, and suggested remedial actions. A holistic view of the interconnectedness of Fe-MOFs structural features, synthetic strategies and applications provides greater insights that highlight challenges hindering their wide-scale industrial applications. Moreover, newer approaches such as utilization of machine learning technique that are providing an opportunity for out-of-sight insights for material design and prediction of material properties are briefly highlighted. Remedial actions for challenges of transitioning Fe-based MOFs towards commercialization and industrial applications are also explored, and suggestions for these aspects are presented.
Interfacial engineering of MoS2 and bimetallic MOF hybrid for superior piezo-photocatalytic hydrogen production and wastewater treatment
(Elsevier, 2025-03) Masekela, Daniel; Yusuf, Tunde Lewis; Balogun, Sheriff A.; Makhado, Edwin; Adeniran, Omolara I.; Modibane, Kwena D.
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Derivatives of pyrazole-based compounds as prospective cancer agents
(American Chemical Society, 2025-03) Ramoba, Lesetja V.; Nzondomyo, Wakopo J.; Serala, Karabo; Macharia, Lucy W.; Biswas, Supratim; Prince, Sharon; Malan, F.P. (Frederick); Alexander, Orbett T.; Manicum, Amanda-Lee E.
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Development of systems thinking in a large first-year Chemistry course using a group activity on detergents
(American Chemical Society, 2025-03) Reynders, Micke; Pilcher, Lynne A.; Potgieter, Marietjie; lynne.pilcher@up.ac.za
Systems Thinking is needed to address global sustainability challenges, yet opportunities to develop this skill set are not routinely included in chemistry curricula. Recurriculation is often a lengthy process, with many barriers slowing efforts to introduce Systems Thinking into chemistry education. Little is known concerning what systems thinking skills can be developed in a stand-alone intervention in a large-scale first-year chemistry course or if such an exercise would be valuable. We investigated student artifacts produced during a group activity on the chemistry and impacts of a surfactant commonly used in laundry detergent for evidence of engagement with Systems Thinking skills and a sustainable-action perspective. An adaptation of a virtual activity described elsewhere was introduced in a second-semester, first-year general chemistry course, coinciding with the introduction to organic chemistry. We used the characteristics of Systems Thinking from the ChEMIST table to explore students’ Systems-Oriented Concept Maps (SOCMEs) and reflections. Students displayed analytical, bridging, and holistic systems thinking skills, especially identifying the parts of a system and viewing it as a whole, organizing the relationships among these parts, identifying relevant system boundaries, and considering the role of humans. However, there was little evidence of engagement with the dynamic nature of systems. Students valued learning the molecular-level chemistry of surfactants, as the context-based approach highlighted the relevance of chemistry in their lives. They endorsed the role of chemistry in sustainability and were motivated to make a difference. The activity conformed to Talanquer’s chemical systems thinking framework and met the primary goal of introducing Systems Thinking in Chemistry Education, to orient Chemistry for sustainability.
Self-regulated learning strategies for success in an online first-year chemistry course
(Royal Society of Chemistry, 2025-01) Rakhunwana, Langanani; Kritzinger, Angelique; Pilcher, Lynne A.; lynne.pilcher@up.ac.za
During their first year of study at university, many students encounter challenges in developing learning strategies that align with success in the courses in which they are enrolled. The emergence of the COVID-19 pandemic heightened the challenges as universities were compelled to transition to online learning. Therefore, this study investigated the self-reported use of learning strategies in a first-year chemistry course delivered online due to the COVID-19 pandemic to identify learning strategies associated with success. Grounded in self-regulated learning (SRL) theory, a case study approach with an explanatory mixed methods design was adopted. Quantitative data were collected using a hybrid of the Motivated Strategies for Learning Questionnaire and the Online Self-regulated Learning Questionnaire. Follow-up open-ended questions were emailed to the students for the qualitative part of the study. Statistical analysis of the quantitative data was performed using SPSS and RUMM2030, while thematic analysis was applied to the qualitative data. Students reported more frequent use of SRL strategies of environment structuring, effort regulation, and elaboration. Conversely, critical thinking, task strategies, help-seeking, and peer learning were reportedly used less often. SRL strategies linked with success in the course were identified as effort regulation, goal setting, and time management. The findings from the qualitative data revealed an impact of online learning due to the pandemic on the use of peer learning and help-seeking strategies. The paper discusses the implications of these findings for educational practices, particularly in the context of hybrid learning in the post-pandemic era.
Piper betle extract inhibits ferroptosis by scavenging oxyradicals, hydroperoxides and inducing NRF2 regulated antioxidants
(Elsevier, 2025-04) Ranganathan, Veena; Deepashree, Vidyaranyapura S.; Gowda, Jadeppa; Dey, Sumit K.; Manjunath, Souparnika H.; Anantharaju, Preethi G.; Bidye, Durgesh Paresh; Pujar, Gurubasavaraj V.; Maharaj, Vinesh J.; Thimmulappa, Rajesh K.
Ferroptosis, an iron catalysed programmed cell death initiated by membrane lipid peroxidation (LPO), is implicated in various degenerative diseases. We screened medicinal/food plants and discovered leaf extract of Piper betle (PB), a popular mouth freshener, as a ferroptosis inhibitor. Compared to vehicle, PB suppressed LPO and inhibited ferroptosis triggered by rotenone or RSL3. Mechanistic studies revealed that PB extract is a powerful lipophilic radical trapping antioxidant and an inducer of Nuclear factor-erythroid 2-Related Factor 2 (NRF2) regulated antioxidant defenses (glutathione/glutathione peroxidase-4 axis). Utilizing diverse free radical systems (hydroxyl, peroxyl, hydroperoxides) and LPO models (serum, LDL), we found that PB extract effectively inhibits LPO by scavenging lipid oxyradicals. LC-HRMS analysis identified hydroxychavicol and polyphenols as the key bioactive constituents in PB extract. In a Drosophila model of rotenone-induced neurotoxicity, PB extract supplementation prevented locomotor deficits and mortality compared to the control diet. In conclusion, PB extract could be developed as a nutraceutical for mitigating ferroptosis-linked disorders.
All-body concept and quantified limits of cooperativity and related effects in homodromic cyclic water clusters from a molecular-wide and electron density-based approach
(Wiley, 2024-12) Cukrowski, Ignacy; Zaaiman, Stefan; Hussain, Shahnawaz; De Lange, Jurgens Hendrik; ignacy.cukrowski@up.ac.za
We strongly advocate distinguishing cooperativity from cooperativity-induced effects. From the MOWeD-based approach, the origin of all-body cooperativity is synonymous with physics- and quantum-based processes of electron (e) delocalization throughout water clusters. To this effect, over 10 atom-pairs contribute to the total e-density at a BCP(H,O) between water molecules in a tetramer. Intermolecular all-body e-delocalization, that is, cooperativity, is an energy-minimizing process that fully explains non-additive increase in stability of a water molecule in clusters with an increase in their size. A non-linear change in cooperativity and cooperativity-induced effects, such as (i) structural (e.g., a change in d(O,O)) or topological intra- and intermolecular properties in water clusters (e.g., electron density or potential energy density at bond critical points) is theoretically reproduced by the proposed expression. It predicted the limiting value of delocalized electrons by a H2O molecule in homodromic cyclic clusters to be 1.58e. O-atoms provide the vast majority of electrons that “travel throughout a cluster predominantly on a privileged exchange quantum density highway” ( O–H O–H O–H ) using Bader's classical bond paths as density bridges linking water molecules. There are, however, additional electron exchange channels that are not seen on molecular graphs as bond paths. A 3D visual representation of the “privileged” and “additional” exchange channels as well as detailed intra- and inter-molecular patterns of e-sharing and (de)localizing is presented. The energy stabilizing contribution made by three O-atoms of neighboring water molecules was found to be large ( 597 kcal/mol in cyclic hexamer) and 5 times more significant than that of a classical O–H O intermolecular H-bond.
Investigating the effects of a context-based laboratory exercise for meaningful learning
(American Chemical Society, 2024-08) Mundy, Christine Elizabeth; Nokeri, Boitumelo K.
We used the context of boot-legging of alcohol to support the concept of matter and separation in the laboratory components of a first-year general chemistry course. The bootlegging laboratory exercise was deployed over two years, Year 1 being online and Year 2 being in a traditional laboratory. Findings over both years indicated that students did significantly better in the context-based lab exercise compared to most traditional laboratory exercises. The use of the Meaningful Learning in the Laboratory Inventory (MLLI) revealed that students came in with high expectations and that cognitive and affective laboratory expectations were met or fell just short in both years. Blended questionnaire items, including both the cognitive and affective in one, showed that the students’ expectations were met in Year 1. In Year 2, most students had good cognitive/affective experiences compared to a wide range of incoming expectations. The majority of students enjoyed the laboratory exercise; reasons for this changed from cognitive in Year 1 to affective in Year 2, coinciding with the change to face to face laboratories, where students could enjoy the excitement of performing the experiments for themselves. The applicability of the context-based experiment resonated with many of the students and prompted a small portion of students to think metacognitively about their laboratory experience and the consequences of chemistry in health, society, and industry. Overall, the introduction of a context-based laboratory exercise provided a more meaningful laboratory experience for students, that is, a deeper learning experience relevant to their everyday lives.
Tin(II)-chloride (SnCl2) mediated reduction of α,(3-alkynyl carbonyl compounds
(Elsevier, 2025-02) Ralepelle, U.; Agbo, E.N.; Lekgau, K.; Chauke, H.; Cukrowski, Ignacy; Nxumalo, Winston
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