Discovery of Aflatoxins and Sterigmatocystins with Antitumor Activity from Aspergillus sp. PQJ‑1 of Sphagneticola trilobata

Fourteen mycotoxins (1–14) were isolated and identified from a Sphagneticola trilobata-derived fungus, Aspergillus sp. PQJ-1, including two new aflatoxins, asperaflatoxins C (3) and D (4), one new sterigmatocystin, Q (7), and 11 known analogues (1, 2, 5, 6, 8–14). Among them, three pairs are epimers (1 and 2, 11 and 12, 13 and 14). Their structures and absolute configurations were determined by NMR, HRESIMS, X-ray diffraction analyses, and ECD calculation. 1 and 2 were isolated as new natural products, with their 13C NMR spectral data reported for the first time. Notably, 4 represents the first compound featuring a unique five-membered lactone carbon skeleton. 1 demonstrated the most cytotoxic effects on HeLa cells with an IC50 value of 5.43 μM. Network pharmacological screening results showed that the mechanism of 1 may be closely related to cell migration and apoptosis. Molecular docking showed that 1 could effectively bind to key target Bcl-2, MMP9, PIK3CA, and EGFR. And the Western blotting experiment confirmed that 1 could down-regulate key proteins such as Bcl-2, MMP9, and EGFR at the protein level. In addition, 1 could up-regulate BAX and down-regulate Bcl-2 and Caspase-3 in mRNA expression based on the qRT-PCR assay. In vivo experiments were also performed for 1.