New citrinin derivatives from the deep-sea-derived fungus Cladosporium sp. SCSIO z015

During the course of our search for novel bioactive compounds from marine fungi, four new citrinin derivatives, cladosporins A-D (1-4) were isolated from a culture broth of the deep-sea-derived fungus Cladosporium sp. SCSIO z015. Their complete structural assignments were elucidated by the extensive spectroscopic investigation. The absolute configurations of 1-3 were established by quantum chemical calculations of the electronic circular dichroism (ECD) spectra. Compounds 1-4 showed weak toxicity towards brine shrine naupalii with LC50 values of 72.0, 81.7, 49.9 and 81.4 mu M, respectively. And 4 also showed significant antioxidant activity against & x251;,alpha-diphenyl-picrylhydrazyl (DPPH) radicals with an IC50 value of 16.4 mu M.