Bioactive fingerprint of <i>Fomitopsis betulina</i> : linking polyamines, phenolics, and functional activities

<i>Fomitopsis betulina</i> (birch polypore) is a medicinal polypore with limited biochemical characterisation. This study provides the first evidence of polyamines and a detailed phenolic profile in the 80% methanolic (MeOH) extract of its fruiting bodies. HPLC analysis revealed spermidine (60.21 ± 0.97 mg/kg d.w.), spermine (41.71 ± 2.56 mg/kg d.w.), and putrescine (0.97 ± 0.10 mg/kg d.w.), with spermidine as the predominant form. Gallic acid (14,415.07 ± 1,297.36 ng/g d.e.) and quinic acid (11,332.40 ± 1,133.24 ng/g d.e.) were accompanied by apiin (514.81 ± 25.74 ng/g d.e.), reported here for the first time in this species. The MeOH extract exhibited notable antioxidant capacity (DPPH: 2.99 ± 0.11 mM TE/g; ABTS: 63.50 ± 0.51 mM TE/g) and strong acetylcholinesterase inhibition (99.03 ± 5.52%). These findings highlight <i>F. betulina</i> as a source of polyamines and phenolics with promising antioxidant and neuroprotective potential.