Isolation of the new polyketide (-)-R-talaropinophiloic acid guided by an integrated metabolomics-dereplication approach.

As part of our ongoing bioprospecting program targeting endophytic fungi, the strain Talaromyces pinophilus J6 was isolated from Euphorbia umbellata. The endophyte metabolic potential was evaluated through a combined metabolomics-dereplication workflow based on an in-house high-resolution mass spectrometry (HRMS) database of Talaromyces metabolites. The strategy enabled rapid annotation of seven metabolites (a-g), allowing rapid characterization of the fungal metabolome and guiding the isolation of potentially new specialized metabolites. Chromatographic fractionation of the crude extract from T. pinophilus J6 cultivated on potato dextrose agar supplemented with ammonium sulfate afforded two polyketides: the new (-)-R-talaropinophiloic acid (1) and the known 3-O-methylfunicone (2). Their chemical structures were determined by Nuclear Magnetic Resonance (NMR), Circular Dichroism (CD), and HRMS analyses. The cytotoxic activities were assessed against the muscle-invasive bladder cancer cell line T24 by MTT assay, yielding IC₅₀ values of 204.70 µM for 1 and 59.68 µM for 2, compared with 6.4 µM for the positive control cisplatin. Assays against the non-tumor RPE-1 cell line showed that 2 displayed a CC₅₀ of 16.62 µM, whereas 1 was non-toxic, highlighting 1 as highly selective for cancer cells. Overall, our results expand knowledge of the chemical diversity of the Talaromyces genus and underscore its potential as a promising source of new bioactive polyketides.