Geothermal pteridophyte endophyte as a potential producer of anti-aggregation metabolites with relevance to neuroprotection

Aim: Neurodegenerative diseases, such as Alzheimer’s, are strongly associated with amyloid-β aggregation. This study aimed to explore bioactive metabolites from endophytic bacteria as potential anti-aggregation agents with relevance to neuroprotection, focusing on isolate D11 obtained from a geothermal fern at Gedong Songo hot springs. Methods: Isolate D11 was characterized by Gram staining and 16S rRNA sequencing. Growth curve analysis was conducted to determine metabolite production phases. Phytochemical screening, bovine serum albumin (BSA) aggregation inhibition assays, liquid chromatography mass spectroscopy (LCMS) profiling, and molecular docking against amyloid-β were employed to evaluate bioactivity and metabolite composition. Results: D11 was identified as a Gram-negative rod with 97.94% similarity to Stutzerimonas stutzeri. Metabolite production peaked during the stationary and death phases. Phytochemical tests revealed alkaloids and tannins in aqueous fractions. BSA aggregation inhibition assays demonstrated potent inhibitory activity, with IC50 values (2.40–3.29 µg/mL) significantly lower than quercetin. LCMS profiling identified diverse metabolites, dominated by flavonoid glycosides such as kaempferol-7-O-deoxyhexosyl-3-O-acetylhexoside, along with alkaloids, peptides, and diterpenoids. Molecular docking confirmed strong binding affinities of flavonoid glycosides to amyloid β (–7.6 kcal/mol), outperforming quercetin (–6.0 kcal/mol). Conclusions: These findings suggest that isolate D11 Stutzerimonas produces bioactive metabolites with anti-aggregation activity and potential relevance to neuroprotection. However, since Stutzerimonas-derived metabolites remain poorly explored and the docking results are tentative, further in-depth characterization and in vivo validation are required to confirm their therapeutic relevance, and further validation using amyloid-β or α-synuclein models is required to confirm therapeutic implications.