Abstract
Six new metabolites, including a pair of inseparable mixtures of secofumitremorgins A (1a) and B (1b), which differed in the configuration of the nitrogen atom, 29-hydroxyfumiquinazoline C (6), 10R-15-methylpseurotin A (7), 1,4,23-trihydroxy-hopane-22,30-diol (10), and sphingofungin I (11), together with six known compounds (2–5 and 8–9), were isolated and identified from the deep-sea sediment-derived fungus Aspergillus fumigatus SD-406. Their structures were determined by detailed spectroscopic analysis of NMR and MS data, chiral HPLC analysis of the acidic hydrolysate, X-ray crystallographic analysis, J-based configuration analysis, and quantum chemical calculations of ECD, OR, and NMR (with DP4+ probability analysis). Among the compounds, 1a/1b represent a pair of novel scaffolds derived from indole diketopiperazine by cleavage of the amide bond following aromatization to give a pyridine ring. Compounds 1, 4, 6, 7, 10 and 11 showed inhibitory activities against pathogenic bacteria and plant pathogenic fungus, with MIC values ranging from 4 to 64 μg/mL.
Highlights
In the course of discovering bioactive metabolites from deep-sea-derived fungi [2,3,4], the fungal strain Aspergillus fumigatus SD-406, which was obtained from sediments collected from the deep-sea in the East China Sea, displayed abundant metabolites and antimicrobial activity in the preliminary screening, and attracted us to perform intensive chemical investigations on it
Six new metabolites, including a mixture of a pair of inseparable isomers, secofumitremorgins A (1a) and B (1b), which differed in the configuration of the nitrogen atom, 29-hydroxyfumiquinazoline C (6), 10R-15-methylpseurotin
The culture broth of fungus Aspergillus fumigatus SD-406 was extracted with EtOAc, and the crude extract was subjected to multiple chromatographic methods to yield subfractions, which were further purified by preparative TLC and semipreparative
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. A (7), 1,4,23-trihydroxy-hopane-22,30-diol (10), and sphingofungin I (11), together with six known compounds, fumitremorgin C (2) [6], 12,13-dihydroxyfumitremorgin C (3) [7], cyclotryprostatin B (4) [8], fumiquinazoline C (5) [9], 14-norpseurotin A (8) [10], and pseurotin A (9) [11] have been isolated and identified (Figure 1). Among these compounds, 1a/1b represent a pair of novel scaffolds derived from indole diketopiperazine by cleavage of the amide bond following aromatization to give a pyridine ring. Details of the isolation and purification, structure elucidation, and biological evaluation of compounds 1–11 are described
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