Production of Unusual Dispiro Metabolites in Pestalotiopsis virgatula Endophyte Cultures: HPLC-SPE-NMR, Electronic Circular Dichroism, and Time-Dependent Density-Functional Computation Study

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• 作者：Julie R. Kesting ; Lars Olsen ; Dan Staerk ; Mysore V. Tejesvi ; Kukkundoor R. Kini ; Harishchandra S. Prakash ; Jerzy W. Jaroszewski
• 刊名：Journal of Natural Products
• 出版年：2011
• 出版时间：October 28, 2011
• 年：2011
• 卷：74
• 期：10
• 页码：2206-2215
• 全文大小：999K
• 年卷期：v.74,no.10(October 28, 2011)
• ISSN：1520-6025

文摘

The endophytic fungus Pestalotiopsis virgatula, derived from the plant Terminalia chebula and previously found to produce a large excess of a single metabolite when grown in the minimal M1D medium, was induced to produce a variety of unusual metabolites by growing in potato dextrose broth medium. Analysis of the fermentation medium extract was performed using an HPLC-PDA-MS-SPE-NMR hyphenated system, which led to the identification of a total of eight metabolites (1鈥?b>8), six of which are new. Most of the metabolites are structurally related and are derivatives of benzo[c]oxepin, rare among natural products. This includes dispiro derivatives 7 and 8 (pestalospiranes A and B), having a novel 1,9,11,18-tetraoxadispiro[6.2.6.2]octadecane skeleton. Relative and absolute configurations of the latter were determined by a combination of NOESY spectroscopy and electronic circular dichroism spectroscopy supported by time-dependent density-functional theory calculations (B3LYP/TZVP level). This work demonstrates that a largely complete structure elucidation of numerous metabolites present in a raw fermentation medium extract can be performed by the HPLC-SPE-NMR technique using only a small amount of the extract, even with unstable metabolites that are difficult to isolate by traditional methods.