Metachelins, Mannosylated and N-Oxidized Coprogen-Type Siderophores from Metarhizium robertsii

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• 作者：Stuart B. Krasnoff ; Ivan Keresztes ; Bruno G. G. Donzelli ; Donna M. Gibson
• 刊名：Journal of Natural Products
• 出版年：2014
• 出版时间：July 25, 2014
• 年：2014
• 卷：77
• 期：7
• 页码：1685-1692
• 全文大小：317K
• ISSN：1520-6025

文摘

Under iron-depleted culture conditions, the entomopathogenic fungus Metarhizium robertsii (Bischoff, Humber, and Rehner) (= M. anisopliae) produces a complex of extracellular siderophores including novel O-glycosylated and N-oxidized coprogen-type compounds as well as the known fungal siderophores N^伪-dimethylcoprogen (NADC) and dimerumic acid (DA). Metachelin A (1), the most abundant component in the M. robertsii siderophore mixture, was characterized as a 1094 Da analogue of NADC that is O-glycosylated by 尾-mannose at both terminal hydroxyl groups and N-oxidized at the dimethylated 伪-nitrogen. The mixture also contained a 1078 Da analogue, metachelin B (2), which lacks the N-oxide modification. Also characterized were the aglycone of 1, i.e., the N-oxide of NADC (3), and the monomannoside of DA (6). N-Oxide and O-glycosyl substituents are unprecedented among microbial siderophores. At high ESIMS source energy and at room temperature in DMSO, 1 underwent Cope elimination, resulting in loss of the N^伪-dimethyl group and dehydration of the 伪鈥撐?bond. High-resolution ESIMS data confirmed that all tri- and dihydroxamate siderophores (1鈥?b>6) complex with trivalent Fe, Al, and Ga. In a chrome azurol S assay, all of the M. robertsii siderophores showed iron-binding activity roughly equivalent to that of desferrioxamine B.