New Prenylated Isoindolinone Alkaloids and Polyketides from the Mangrove-Derived Fungus Aspergillus sp. SCSIO 41440

New prenylated isoindolinone alkaloids, aspernidines C-E (1–3), a new diketopiperazine alkaloid, protubonine C (4), and new polyketides, (±)-asperisocoumarin J and asperisocoumarin K (5 and 6), were isolated from the mangrove-derived fungus Aspergillus sp. SCSIO 41440, together with six known compounds (7–12). Comprehensive NMR and mass spectrometric analysis, single-crystal X-ray diffraction, and calculated electronic circular dichroism (ECD) were employed for the structural elucidation and stereochemical assignment of these compounds. All compounds were evaluated for their acetylcholinesterase (AChE) inhibitory activity. Compound 10 exhibited potent AChE inhibition with an IC50 value of 3.16 ± 1.16 μM. Molecular docking analysis further revealed that 10 binds strongly to the AChE active site (PDB: 4EY7). These findings suggest that compound 10 represents a candidate scaffold for further investigation as an AChE inhibitor.