Three new polyketides isolated from the Karst cave-derived <i>Streptomyces</i> sp. FD-2-6

Three new polyketides, actinofuranones J (<b>1</b>) and K (<b>2</b>), nocapyrone S (<b>3</b>), with one known compound nocapyrone Q (<b>4</b>) were isolated from the culture broth of a Karst cave-derived <i>Streptomyces</i> sp. (FD-2-6). Their structures were elucidated by comprehensive analysis of NMR spectroscopic data, HR-MS and electronic circular dichroism (ECD) data. The antitumour and antibacterial activities of <b>1-4</b> were investigated by examining their IC₅₀ and MIC values in MCF-7 human breast cancer cells, human hepatocellular carcinoma HepG2 cells and human cervical cancer Hela cells, and <i>Klebsiella pneumoniae</i> sp, <i>Pseudomonas aeruginosa</i> sp, <i>Mycolicibacterium smegmatis</i> sp, <i>Escherichia coli</i> sp, <i>Staphylococcus aureus</i> sp. Compounds <b>1-4</b> showed weak inhibitory effect on antitumour activity on MCF-7 human breast cancer cells, and human cervical cancer Hela cells.