Banksialactones and Banksiamarins: Isochromanones and Isocoumarins from an Australian Fungus, Aspergillus banksianus
journal contributionposted on 2018-06-19, 14:23 authored by Nirmal K. Chaudhary, John I. Pitt, Ernest Lacey, Andrew Crombie, Daniel Vuong, Andrew M. Piggott, Peter Karuso
Chemical investigation of an Australian fungus, Aspergillus banksianus, led to the isolation of the major metabolite banksialactone A (1), eight new isochromanones, banksialactones B–I (2–9), two new isocoumarins, banksiamarins A and B (10 and 11), and the reported compounds, clearanol I (12), dothideomynone A (13), questin (14), and endocrocin (15). The structures of 1–11 were established by NMR spectroscopic data analysis, and the absolute configurations were determined from optical rotations and ECD spectra in conjunction with TD-DFT calculations. The secondary metabolite profile of A. banksianus is unusual, with the 11 most abundant metabolites belonging to a single isochromanone class. Conjugation of 1 with endocrocin, 5-methylorsellinic acid, 3,5-dimethylorsellinic acid, mercaptolactic acid, and an unknown methylthio source gave rise to five unprecedented biosynthetic hybrids, 5–9. The isolated compounds were tested for cytotoxicity, antibacterial, and antifungal activities, with hybrid metabolites 7–9 displaying weak cytotoxic and antibiotic activities.
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methylthio sourcebiosynthetic hybridsNMR spectroscopic data analysiscompoundantifungal activitiesantibiotic activitiesAspergillus banksianusisochromanone classmetabolite profileAspergillus banksianus Chemical investigationmercaptolactic acidTD-DFT calculationsAustralian Fungusmetabolite banksialactoneECD spectraAustralian fungusendocrocin5- methylorsellinic acid