| Affiliation: | 1. School of Pharmacy, Sungkyunkwan University, Suwon, 16419 (Republic of Korea Department of Chemistry, Princeton University, New Jersey, 08544 USA;2. Chemical Biology of Microbe-Host Interactions, Hans-Knöll Institute (HKI), Beutenbergstraße 11a, 07745 Jena, Germany;3. School of Pharmacy, Sungkyunkwan University, Suwon, 16419 (Republic of Korea;4. Department of Systems Biotechnology, Chung-Ang University, Anseong, 17546 Republic of Korea;5. Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Hatfield, 0028 Pretoria, South Africa |
| Abstract: | In this study, we analyzed if Actinomadura sp. RB99 produces siderophores that that could be responsible for the antimicrobial activity observed in co-cultivation studies. Dereplication of high-resolution tandem mass spectrometry (HRMS/MS) and global natural product social molecular networking platform (GNPS) analysis of fungus-bacterium co-cultures resulted in the identification of five madurastatin derivatives (A1, A2, E1, F, and G1), of which were four new derivatives. Chemical structures were unambiguously confirmed by HR-ESI-MS, 1D and 2D NMR experiments, as well as MS/MS data and their absolute structures were elucidated based on Marfey's analysis, DP4+ probability calculation and total synthesis. Structure analysis revealed that madurastatin E1 ( 2 ) contained a rare 4-imidazolidinone cyclic moiety and madurastatin A1 ( 5 ) was characterized as a Ga3+-complex. The function of madurastatins as siderophores was evaluated using the fungal pathogen Cryptococcus neoformans as model organism. Based on homology models, we identified the putative NRPS-based gene cluster region of the siderophores in Actinomadura sp. RB99. |
