http://hdl.handle.net/11189/1930 2026-11-12T15:23:50Z http://hdl.handle.net/11189/11012 Title: Bioactive chalcones from Aizoon africanum: isolation and cytotoxicity against liver and neural cancer cells Authors: ELTAHIR, ALI OMER ELSSMANI; Abdul, Naeem Sheik; Docrat, Taskeen; Bristow, Paolo; Chipofya, Elias; Luckay, Robert; Nyila, Monde; Marnewick, Jeanine L; Ndjoubi Ossamy, Kadidiatou; Hussein, Ahmed A. Abstract: Aizoon africanum (L.) Klak (Synonym Galenia africana L.) is traditionally used for a variety of medicinal purposes; however, it has been reported to cause liver damage and severe ascites, particularly in sheep and Angora goats in the arid regions of the Western Cape. This study explores its cytotoxic properties to identify potential cytotoxic compound(s) in the plant. The methanolic extract of A. africanum was re-investigated and subjected to various chromatographic techniques, including preparative HPLC, resulting in the isolation of eight compounds (1–8). Structural elucidation was primarily based on NMR data. Among the isolated compounds, four were flavanones, one was a flavonone, and three were chalcones. Notably, compound 8 was identified as a new chalcone, while compounds 2 and 3 were reported for the first time from this plant. The toxicity of these isolated compounds was evaluated against the HepG2 and SH-SY5Y cancer cell lines using the MTT assay. We further investigated markers of cell death using spectrophotometric and luminometric methods. Among the isolated compounds, 7 and 8 exhibited cytotoxic activities within the range of 3.0–20.0 µg/mL. Notably, the compounds demonstrated greater cytotoxicity towards liver-derived HepG2 cells compared to the neuronal SH-SY5Y cell line. Compound 7 (2′,4′-dihydroxychalcone) was identified as inducing apoptosis through the intrinsic pathway without causing overt necrosis. The findings indicate that the phytochemicals derived from A. africanum exhibit differential cytotoxic effects based on cell type, suggesting potential for developing novel anticancer agents, particularly compound 7. Additionally, the identification of compound 8 provides insight into the liver toxicity of this plant observed in sheep in South Africa. 2025-01-01T00:00:00Z http://hdl.handle.net/11189/11011 Title: Chronic stress elicits sex-specific mitochondrial respiratory functional changes in the rat heart Authors: Odendaal- Gambrell, Caitlin P.; O'Brien, Cassidy; Cairns, Megan; Maarman, Gerald J.; Joseph, Danzil E.; Smith, Carine; Rautenbach, Fanie; Marnewick, Jeanine L; Essop, Faadiel Abstract: Although chronic psychosocial stress is linked to cardiovascular diseases, the underlying mechanisms remain elusive. For this study, we focused on the mitochondrion as a putative mediator of stress-related cardiac pathologies in a sex-dependent manner. Male and female Wistar rats were subjected to chronic stress for 4 weeks (mimicking an anxious phenotype) versus matched controls. Cardiac redox status, mitochondrial respiration parameters, and expression levels of proteins involved in mitochondrial oxidative phosphorylation, dynamics, and biogenesis were evaluated. Despite limited changes in behavior and circulating stress hormones (both sexes), stressed males exhibited altered cardiac oxidative phosphorylation via β-oxidation- and glucose oxidation-linked respiratory pathways together with increased myocardial antioxidant capacity and decreased lipid peroxidation. Conversely, stressed females exhibited a protective and resilient phenotype by displaying augmented levels of major mitochondrial respiratory complexes (complex I, III, and ATP synthase) and a fusion marker (mitofusin-2 [Mfn2]), together with attenuated expression of a fission marker (dynamin-related protein-1 [Drp1]) despite decreased estradiol levels. In contrast, stressed males displayed increased cardiac ATP synthase levels together with diminished peroxisome proliferator-activated receptor-gamma coactivator-1-alpha (PGC-1α) expression versus controls. These findings indicate that male mitochondria are more prone to stress-related functional changes, while females exhibited a more protective and resilient phenotype. 2025-01-01T00:00:00Z http://hdl.handle.net/11189/11010 Title: An investigation into the sex dependence of post-reperfusion cardiac mitochondrial function and redox balance in chronically stressed rats Authors: Cairns, Megan; Andrews, Jasmine; Odendaal, Caitlin; O'Brien, Cassidy ; Marais, Erna; Maarman, Gerald; Sishi, Balindiwe; Joseph, Danzil; Rautenbach, Fanie; Marnewick, Jeanine L; Essop, Faadiel Abstract: Although mitochondrial alterations are implicated in cardiac pathologies, sex-specific changes following chronic stress and ischemia–reperfusion injury are poorly characterized. Male and female Wistar rats underwent chronic restraint stress (CRS) for 4 weeks versus controls, whereafter ex vivo hearts were subjected to regional ischemia and reperfusion. Post-reperfusion hearts were dissected into ischemia-reperfused and non-ischemic regions with high-resolution mitochondrial respirometry, and oxidative stress assays performed. CRS males displayed increased routine and fatty acid β-oxidation respiration in non-ischemic tissues but lowered ETF-linked LEAK contributions to overall electron transfer system capacity ratios in ischemia-reperfused regions versus controls. CRS males exhibited lowered superoxide dismutase activity and increased lipid peroxidation in well-perfused regions versus controls. Female CRS hearts showed attenuated ETF-linked LEAK respiration and increased lipid peroxidation versus controls in non-ischemic tissue but a lowered RE ratio (measure of mitochondrial coupling) with ischemia–reperfusion. Our findings highlight the heart's sexually dimorphic response to chronic stress and ischemic injury, with female hearts showing oxidative damage in non-ischemic tissues together with relatively intact mitochondrial function in ischemia-reperfused tissues. 2025-01-01T00:00:00Z http://hdl.handle.net/11189/11009 Title: A standardised exercise protocol to induce oxidative stress in humans: validation with a dietary polyphenol intervention Authors: Kamati, Oiva; Bragagna, Laura; Bester, Dirk; Wagner, Karl-Heinz; Stürmer, Vera; Gassner, Markus; Maqboul, Lina; Louw, Roan; West, Sacha; Davies, Simeon; Marnewick, Jeanine L Abstract: Background: Generating oxidative stress in a predictable and controllable way without the risk of causing harm is important for enabling the safe validation of interventions such as dietary polyphenols and ensuring ethical standards in human studies, while also advancing mechanisms involved in the induced oxidative stress. Although, many experimental animal and in vitro models have been developed to conduct oxidative stress-based research, to date, very few reliable human models are available. Objective: This study’s main objective was to establish a standardised exercise model to induce oxidative stress in a repeatable and controllable manner and was tested with dietary polyphenols. Method: We applied a single blinded, randomised, cross-over, placebo-controlled trial with adult (25.95 ± 6.25 years) males (N = 40) where the induction of oxidative stress was achieved by an incremental aerobic exercise activity followed by a maximal anaerobic activity until exhaustion. To assess the model, rooibos polyphenolics was used as one of the interventions, while markers of safety and oxidative stress were measured on various occasions during the trial period. Results: The exercise regime reliably and repeatably induced oxidative stress, evidenced by increased levels of oxidative damage markers, i.e., oxidised glutathione (p = 0.003), malondialdehyde (p = 0.004), and a Comet assay tail moment (p < 0.05), while unconjugated bilirubin (p = 0.002) and the ferric reducing antioxidant potential (p < 0.001) increased over the study period, in the male study participants, irrespective of the oral intervention. Conclusions: This model showed an exercise regime that could be adapted to induce oxidative stress in a reliable and repeatable fashion without risk of causing harm. This study also demonstrated that a dietary polyphenolic intervention with rooibos did not complicate the onset of oxidative stress. 2025-01-01T00:00:00Z