Rising drug resistance limits the treatment options infected by methicillin-resistantStaphylococcus aureus(MRSA). A promising solution for overcoming the resistance of MRSA is to inhibit the penicillin-binding protein 2a (PBP2a). A novel terpene-polyketide hybrid meroterpenoid, aspermerodione (1), characterized by an unusual 2,6-dioxabicyclo[2.2.1]heptane core skeleton, and a new heptacyclic analogue, andiconin C (2), were isolated and identified from the liquid cultures of endophytic fungusAspergillussp. TJ23. The structures and their absolute configurations of all chiral centers were elucidated via extensive spectroscopic analyses and electronic circular dichroism (ECD) calculations and determined via single-crystal X-ray diffraction analysis. Aspemerodione (1) was found to be a potential inhibitor of PBP2a, and work synergistically with theβ-lactam antibiotics oxacillin and piperacillin against MRSA.

Chemical investigation of the extracts of Aspergillus terreus resulted in the identification of terreusterpenes A–D (1–4), four new 3,5-dimethylorsellinic acid-based meroterpenoids. The structures and absolute configurations of 1–4 were elucidated by spectroscopic analyses including HRESIMS and 1D- and 2D-NMR, chemical conversion, and single crystal X-ray diffraction. Terreusterpenes A (1) and B (2) featured 2,3,5-trimethyl-4-oxo-5-carboxy tetrahydrofuran moieties. Terreusterpene D (4) was characterized by a 4-hydroxy-3-methyl gamma lactone fragment that was generated by accident from the rearrangement of 3 in a mixed tetrahydrofuran–H₂O–MeOH solvent. All these compounds were evaluated for the β-site amyloid precursor protein-cleaving enzyme 1 (BACE1) and acetylcholinesterase (AchE) inhibitory activities. Among them, compounds 1 and 2 showed potentially significant BACE1 inhibitory activity, with IC₅₀ values of 5.98 and 11.42 μM, respectively. Interestingly, compound 4 exhibited promising BACE1 and AchE inhibitory activities, with IC₅₀ values of 1.91 and 8.86 μM, respectively, while 3 showed no such activity. Taken together, terreusterpenes A and B could be of great importance for the development of new BACE1 inhibitors, while terreusterpene D could serve as the first dual-targeted 3,5-dimethylorsellinic acid-based meroterpenoid for the treatment of Alzheimer's disease.