Fluorescent azaphilonoidal pigments from the endophytic fungus Biscogniauxia sp.

As part of our continuing search for novel cytotoxic fungal compounds, the entophytic fungus Biscogniauxia sp. (Xylariaceae) was isolated from a Bromelia species collected in the Ecological Reserve on the campus of the National Autonomous University of Mexico. Fungal identification was assessed by nuclear ribosomal internal transcribed spacer (ITS) barcoding. The organic (CHCl₃-MeOH) extract from the axenic solid (moisture rice) culture showed promising growth inhibition activity when tested at 20 µg/mL against HCT-15 (colorectal) and HeLa (cervix) cell lines (96.5 and 96.3% of inhibition, respectively). Dereplication results of the organic extract by UPLC-PDA-HRESI-MS/MS against a database containing more than 200 fungal secondary metabolites revealed the presence of the dimeric tetrahydroxanthone secalonic acid G. From this extract, a series of known and new fluorescent azaphilonoidal pigments were isolated. Their structures were elucidated using a set of spectroscopic and spectrometric techniques. In addition, these compounds were tested for antiproliferative activity against a panel of cancer cell lines.