Isolation and Characterisation of Alkaloids from Marine-Derived Aspergillus fumigatus SYPHU504 with Antiproliferative Activity

Four novel alkaloids, including three γ-lactam alkaloids (1–3) and one diketopiperazine (4), along with eight previously known compounds (5–12), were isolated from the marine-derived fungus Aspergillus fumigatus SYPHU504. Their structures, including the tentative stereochemical assignments of the side-chain double bonds in 2 and 3, were elucidated through comprehensive spectroscopic analysis and in comparison with the literature’s data. All isolated compounds were evaluated for their anti-leukaemic activities against human leukaemia cell lines K562 and RS4;11 using the MTT assay. Compounds 4, 6, 7, and 9–12 exhibited notable cytotoxic activities against both RS4;11 and K562 cell lines, with IC50 values ranging from 5.02 ± 2.33 to 31.85 ± 0.50 μM. The results of Western blotting and Annexin V-FITC/PI staining elucidated that compounds 4, 7, and 10 could induce apoptosis in both RS4;11 cells and K562 cells.