Camelliasaponin B1, a Saponin from Camellia oleifera Seed, Protects Against Oxidative Stress and Is Associated with Reduced BNIP3/NIX-LC3B Expression in PC12 Cells

Camelliasaponins, bioactive constituents abundant in the by-products of Camellia oleifera oil production, exhibit diverse biological activities. However, their potential in regulating neuroprotective mitophagy remains largely unexplored. This study identifies camelliasaponin B1 (CSB1) as an abundant component in C. oleifera seeds and investigates its cytoprotective mechanisms against oxidative stress. Using an in vitro model of H2O2-induced oxidative damage in PC12 cells, we found that CSB1 pretreatment significantly alleviated oxidative stress, as evidenced by reduced reactive oxygen species (ROS) accumulation and enhanced antioxidant enzyme activities (SOD, CAT, GSH-Px). CSB1 also preserved mitochondrial function, restoring membrane potential (ΔΨm), ultrastructure, and respiratory capacity. Mechanistically, CSB1 reduces the expression of BNIP3/NIX-LC3B pathway-related proteins, suggesting a modulatory effect on mitophagy, as supported by transcriptomic analysis, Western blotting, and immunofluorescence. Molecular docking computationally predicted potential interactions between CSB1 and BNIP3/NIX proteins, which require experimental validation. Collectively, these findings suggest that CSB1 acts as a cytoprotective agent that enhances antioxidant defenses, safeguards mitochondrial integrity, and is associated with reduced BNIP3/NIX-LC3B expression and co-localization, offering a potential molecular basis for its development as a neuroprotective agent targeting oxidative stress-related mitochondrial dysfunction.