Pyrenosetin D, a New Pentacyclic Decalinoyltetramic Acid Derivative from the Algicolous Fungus Pyrenochaetopsis sp. FVE-087

The fungal genus is commonly found in soil, terrestrial, and marine environments, however, has received little attention as a source of bioactive secondary metabolites so far. In a recent work, we reported the isolation and characterization of three new anticancer decalinoyltetramic acid derivatives, pyrenosetins A-C, from the Baltic -derived endophytic fungus sp. FVE-001. Herein we report a new pentacyclic decalinoylspirotetramic acid derivative, pyrenosetin D ( ), along with two known decalin derivatives wakodecalines A ( ) and B ( ) from another endophytic strain FVE-087 isolated from the same seaweed and showed anticancer activity in initial screenings. The chemical structures of the purified compounds were elucidated by comprehensive analysis of HR-ESIMS, FT-IR, [a] , 1D and 2D NMR data coupled with DFT calculations of NMR parameters and optical rotation. Compounds were evaluated for their anticancer and toxic potentials against the human malignant melanoma cell line (A-375) and the non-cancerous keratinocyte cell line (HaCaT). Pyrenosetin D ( ) showed toxicity towards both A-375 and HaCaT cells with IC values of 77.5 and 39.3 μM, respectively, while and were inactive. This is the third chemical study performed on the fungal genus and the first report of a pentacyclic decalin ring system from the fungal genus .