β-Carotene induces context-dependent redox remodeling in gastric cancer cells following comparative carotenoid screening: Integrated electronic, membrane, and metabolomic analysis.

Carotenoids are traditionally described as antioxidants; however, their biological activity depends on cellular and environmental context. In tumor cells with dysregulated redox homeostasis, it remains unclear whether β-carotene stabilizes redox balance or instead induces dose-dependent redox shifts. A comparative screening of five carotenoids, including fucoxanthin, astaxanthin, zeaxanthin, lutein, and β-carotene, identified β-carotene for mechanistic evaluation in AGS gastric cancer cells. We investigated the context-dependent redox behavior of β-carotene in AGS cells using an integrated multiscale approach combining cellular assays, electronic-structure calculations, membrane modeling, and nuclear magnetic resonance (NMR)-based metabolomics. Cytotoxicity analysis revealed an IC50 of 60.36 ± 1.84 μM in AGS cells. Reactive oxygen species (ROS) measurements showed a transient intracellular ROS increase between 6 and 12 h, followed by attenuation later, indicating dynamic redox modulation rather than sustained oxidative stress. Density functional theory calculations demonstrated environment-dependent electronic properties enabling radical stabilization. Molecular dynamics simulations showed stable localization of β-carotene within the low-dielectric hydrophobic core of lipid bilayers, supporting a membrane microenvironment favorable for redox interactions. Metabolomic profiling revealed coordinated dose-dependent metabolic remodeling. At IC50 exposure, NADPH levels decreased to 0.65-fold relative to control, accompanied by reductions in glutathione (0.63-fold) and glutamate (0.63-fold), indicating depletion of reducing equivalents. In parallel, oxidative modification markers increased markedly, with methionine sulfoxide rising 7.05-fold and lactate increasing 1.24-fold, suggesting secondary metabolic adjustments linked to redox perturbation. Together, these findings are consistent with context-dependent redox-associated metabolic remodeling under β-carotene exposure, linking molecular electronic properties, membrane localization, and intracellular metabolic responses.