Two New Citrinin Derivatives From the Marine Sponge-Derived Fungus Aspergillus sp. S4I4-4

Two new citrinin derivatives, xanone (1) and aspercitrinin (2), together with seven known ones (3-9), were isolated from the marine sponge-derived fungus Aspergillus sp. S4I4-4. Their structures with absolute configurations were determined by spectroscopic methods (UV, IR, MS, and NMR), x-ray diffraction analysis and ECD calculation. Compound 1 was the fifth example of citrinin dimer bearing a 5/6/6/6 skeleton with a disclosed pyran ring isolated from natural sources. Notably, compound 1 exhibited potent to moderate cytotoxic activity against eight tumor cell lines, with IC₅₀ values ranging from 3.43 to 19.71 µM and cisplatin served as the positive control. Compound 1 also demonstrated significant antibacterial activities against Enterococcus faecalis ATCC 29212 with a MIC value of 4 µg/mL and ciprofloxacin served as the positive control.