Paolo Bristow

The exploration of natural redox-modulating agents to mitigate/reduce oxidative damage triggered by toxins is a major area of interest in nutritional and pharmacological fields. Aspalathus linearis (rooibos), traditionally consumed in South Africa for health benefits, was assessed for hepatoprotective effects against fumonisin B1 (FB1)-induced damage. This study involved 24 male rats (n = 6/group) that received FB1 (50 mg/kg diet equivalent, i.p. for 5 days) with or without oral exposure to unfermented (GR) or fermented (FR) rooibos extracts. Alongside somatic records, we assessed blood biochemicals, as well as liver histology, antioxidative stress markers (GSH, GPx, MDA, and carbonylation), regulatory proteins (Nrf2, Sirt3, PGC-α, TRX1, HSP70, and LONp1), inflammation (cytokines), and phospholipid fatty acid profile. Based on results, FB1 suppressed growth, compromised liver function, altered redox status, and elevated stress markers. Both rooibos extracts decreased oxidative damage (↓MDA, ↓carbonylation) and modulated stress regulators (↑Nrf2, ↓HSP70). FR uniquely increased GPx and TRX1 while decreasing IL-1β and PGC-α concentrations, whereas GR strongly increased Nrf2 and Sirt3, reflecting distinct bioactivities linked to their differing polyphenolic profiles. Neither extract compensated for FB1-induced alterations in the liver total phospholipid fatty acid profile or serum cholesterol. In conclusion, GR and FR improved redox potential and inflammatory/stress response; however, this effect was selective, as it did not translate into comprehensive hepatoprotection. These findings support the potential role of rooibos as a dietary modulator of endogenous antioxidant defenses, although clinical translational trials are needed.

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.