Bioactive Naphtho-α-Pyranones from Two Endophytic Fungi of the Genus .

In the course of our survey to study the metabolic potential of two species of a new helotialean genus , namely and , their crude extracts were obtained using different cultivation techniques, which led to the isolation and characterization of two new naphtho--pyranone derivatives recognized as a monomer () and its 6,6'-homodimer () together with two known diketopiperazine congeners, outovirin B () and (3,6)-3,6-dibenzylpiperazine-2,5-dione (). The structures of isolated compounds were determined based on extensive 1D and 2D NMR and HRESIMS. The absolute configuration of new naphtho--pyranones was determined using a comparison of their experimental ECD spectra with those of related structural analogues. 6,6'-binaphtho--pyranone talaroderxine C () exhibited potent cytotoxic activity against different mammalian cell lines with IC values in the low micromolar to nanomolar range. In addition, talaroderxine C unveiled stronger antimicrobial activity against rather than with MIC values of 0.52 µg mL (0.83 µM) compared to 66.6 µg mL (105.70 µM), respectively.