The aim of this study was to investigate the metabolites in Aspergillus subramanianii 1901NT-1.40.2 extract using UPLC-MS, isolate and elucidate the structure of individual compounds, and study the antimicrobial and cytotoxic activities of the isolated compounds. The structures of two previously unreported ergostane triterpenoid aspersubrin A (1) and pyrazine alkaloid ochramide E (2) were established using NMR and HR ESI-MS. The absolute configuration of 1 was determined using quantum chemical calculations. Moreover, the known polyketides sclerolide (3) and sclerin (4); the indolediterpene alkaloid 10,23-dihydro-24,25-dehydroaflavinine (5); the bis-indolyl benzenoid alkaloids kumbicin D (6), asterriquinol D dimethyl ether (7), petromurin C (8); and the cyclopentenedione asterredione (9) were isolated. The effects of compounds 3-9 on the growth and biofilm formation of the yeast-like fungus Candida albicans and the bacteria Staphylococcus aureus and Escherichia coli were investigated. Compounds 5 and 6 inhibited C. albicans growth and biofilm formation at an IC₅₀ of 7–10 µM. Moreover, the effects of compounds 3-9 on non-cancerous H9c2 cardiomyocytes, HaCaT keratinocytes, MCF-10A breast epithelial cells, and breast cancer MCF-7 and MDA-MB-231 cells were also investigated. Compound 8 (10 µM) significantly decreased the viability of MCF-7 cells, inhibited colony formation, and arrested cell cycle progression and proliferation in monolayer culture. Moreover, 8 significantly decreased the area of MCF-7 3D spheroids by approximately 30%. A competitive test with 4-hydroxytamoxyfen and molecular docking showed that estrogen receptors (ERβ more than ERα) were involved in the anticancer effect of petromurin C (8).

Background: Mycophenolic acid (MPA) is an IMPDH inhibitor used clinically as an immunosuppressant, but its antiproliferative potency is offset by immune toxicity. We previously identified marine-derived MPA analogues as candidate estrogen receptor α (ERα) ligands. Here, we tested whether penicacid G (PG), a C-4′-oxidized MPA derivative from the marine fungus Penicillium sp. 1901NT-2.53.1, exerts ERα-dependent antiproliferative activity against ER-positive breast cancer cells. Methods: Molecular targets were predicted with TargetNet and OCHEM QSAR models; ERα binding was modeled by docking (PDB 3UUD) and 100 ns molecular dynamics. Cytotoxicities of PG, 4′-hydroxy-MPA, and MPA were determined in MCF-7, MDA-MB-231, H9c2, and MonoMac-1 cells. ERα dependence was interrogated by 4-hydroxytamoxifen (4-OHT) competition, clonogenic assay, ERα monomer/dimer analysis, qPCR of ER-regulated transcripts, cell-cycle flow cytometry, and LINCS L1000 analysis. Results: PG docked into the ERα ligand-binding pocket (−7.7 kcal/mol) and remained stably bound over 100 ns. PG reduced MCF-7 viability at 1 μM (−19.4%) without affecting MDA-MB-231, H9c2, or MonoMac-1 cells (IC50 > 100 μM) and inhibited MCF-7 colony formation (IC50 3.1 μM). Its effect was attenuated by 4-OHT and accompanied by altered ERα monomer/dimer ratios, rapid PHB2 upregulation, and IGFBP4 suppression, indicating ERα pathway engagement. In contrast, MPA inhibited both cancer cell lines, was not blocked by 4-OHT, and its LINCS L1000 profile suggests indirect antagonism of ER-dependent transcription secondary to nucleotide depletion. Conclusions: Penicacid G is an ERα-engaging MPA analogue that selectively impairs ER-positive breast cancer cell proliferation while sparing monocytic immune cells, representing a promising ERα-targeted lead scaffold.