TMC-256A1

It is generally accepted that fungi have a number of dormant gene clusters for the synthesis of secondary metabolites, and the activation of these gene clusters can expand the diversity of secondary metabolites in culture. Recent studies have revealed that the mycolic acid-containing bacterium Tsukamurella pulmonis activates dormant gene clusters in the bacterial genus Streptomyces. However, it is not clear whether the mycolic acid-containing bacteria activate dormant gene clusters of fungi. We performed co-culture experiments using marine-derived Aspergillus niger with Mycobacterium smegmatis, a mycolic acid-containing bacteria. The co-cultivation resulted in the production of a pigment by A. niger and increased cytotoxic activity of the extract against human prostate cancer DU145 cells. An analysis of secondary metabolites in the extract of the co-culture broth revealed that the increase in cytotoxic activity was caused by the production of malformin C (1), and that TMC-256A1 (2), desmethylkotanin (3), and aurasperone C (4) were selectively produced under co-culture conditions. In addition, further study suggested that direct interaction between the two microorganisms was necessary for the production of the pigment and the cytotoxic compound malformin C (1) from A. niger. Given the biological activities of malformin C, including cytotoxic activity, our approach for increasing the production of bioactive secondary metabolites has important practical applications and may facilitate structural analyses of novel bioactive compounds.

Capillasterin A (1), a novel pyrano[2,3-f]chromene, together with seven known naphthopyrones including comaparvin (2), TMC-256C1 (3), 6-methoxycomaparvin-5- methyl ether (4), 5,8-dihydroxy-6-methoxy-2-propyl-4H-naphtho[2,3-b]pyran-4-one (5), 5,8-dihydroxy-6,10-dimethoxy-2-propyl-4H-naphtho[2,3-b]pyran-4-one (6), TMC-256A1 (7) and 6-methoxycomaparvin (8) were isolated from an EtOH/H₂O extract from the Australian crinoid Capillaster multiradiatus. The structures of all the compounds were determined by detailed spectroscopic (1D/2D NMR and MS) data analysis. This is the first report of a natural product that contains the pyrano[2,3-f]chromene skeleton. Compounds 2⁻6 were observed to display moderate inhibition of in vitro HIV-1 replication in a T cell line with EC50 values ranging from 7.5 to 25.5 µM without concomitant cytotoxicity.

The addition of metal bromides (NaBr and CaBr2) during fermentation of the marine-mudflat-derived fungus Aspergillus niger induced production of a new radical scavenging brominated naphthopyranone, 6,9-dibromoflavasperone (1); and three known naphtho-γ-pyranone monomers, flavasperone (2), TMC-256A1 (3), and fonsecin (4); and one naphtho-γ-pyranone dimer, aurasperone B (5). The structure of 6,9-dibromoflavasperone (1) was assigned through the combination of spectroscopic data analyses and comparison with the spectral data of flavasperone (2). Compounds 1-5 displayed potent radical scavenging activity against 2,2-diphenyl-1-picrylhydrazyl, with IC50 values of 21, 25, 0.3, 0.02, and 0.01 μM, respectively, and 3-5 were more potent than the positive control, ascorbic acid (IC50, 20.0 μM).