Hybrid Polyketides from a Hydractinia-Associated Cladosporium sphaerospermum SW67 and Their Putative Biosynthetic Origin

摘要

Five hybrid polyketides ( , , and – ) containing tetramic acid core including a new hybrid polyketide, cladosin L ( ), were isolated from the marine fungus SW67, which was isolated from the marine hydroid polyp of . The hybrid polyketides were isolated as a pair of interconverting geometric isomers. The structure of was determined based on 1D and 2D NMR spectroscopic and HR-ESIMS analyses. Its absolute configuration was established by quantum chemical electronic circular dichroism (ECD) calculations and modified Mosher’s method. Tetramic acid-containing compounds are reported to be derived from a hybrid PKS-NRPS, which was also proved by analyzing our C-labeling data. We investigated whether compounds – could prevent cell damage induced by cisplatin, a platinum-based anticancer drug, in LLC-PK1 cells. Co-treatment with and ameliorated the damage of LLC-PK1 cells induced by 25 μM of cisplatin. In particular, the effect of compound at 100 μM (cell viability, 90.68 ± 0.81%) was similar to the recovered cell viability of 88.23 ± 0.25% with 500 μM -acetylcysteine (NAC), a positive control.