Psychrophilin E, a new cyclotripeptide, from co-fermentation of two marine alga-derived fungi of the genus Aspergillus

Chemical investigation of the mycelial extract of a mixed culture of two marine alga-derived fungal strains of the genus Aspergillus has yielded one new cyclotripeptide, psychrophilin E (1), the recently reported oxepin-containing alkaloids, protuboxepin A (2) and oxepinamide E (3), together with three other polyketide derivatives (4-6). The chemical structure and relative and absolute configurations of psychrophilin E (1) were unambiguously established based on HRMS, 1D, 2D NMR and chiral-phase HPLC analysis of its hydrolysate. All the isolated compounds were assessed for their anti-proliferative activity against four different human cancer cell lines and some of them revealed selective activities.