Neuroprotective and antioxidant effects of fermented spent coffee ground fractions against Alzheimer's-related oxysterol 27-hydroxycholesterol in SH-SY5Y neuronal cells

Spent coffee grounds (SCG) constitute a phenolic-rich agro-industrial residue with underexplored biomedical potential. This study developed a sequential bioprocess comprising solid-state fermentation, hydroalcoholic extraction, and ultrafiltration to selectively enrich low-molecular-weight phenolic fractions and assess their effects in Alzheimer's-related stress conditions. Phenolic compounds Total (TPC) and composition were quantified, and bioactivity was assessed in SH-SY5Y neuronal cells exposed to hydrogen peroxide (H₂O₂) or the oxysterol 27-hydroxycholesterol (27-OHC), a key driver of redox imbalance and amyloidogenic pathways. Assessed parameters included cell density and viability, reactive oxygen species (ROS), superoxide dismutase (SOD) activity and amyloid-β peptide 40 (Aβ40) accumulation. Bioprocessing enhanced the total phenolic content by up to 4.2-fold and redirected the metabolite profiles toward highly diffusible, low-molecular-weight compounds. The '3 kDa fraction exhibited the strongest functional response, markedly suppressing ROS generation (∼90%), restoring SOD activity and reducing Aβ40 levels under 27-OHC challenge. These results evidence an enrichment strategy that yields SCG-derived fractions with potent antioxidant and neuroprotective properties.