Abstract
Marine-derived fungi are considered to be valuable producers of bioactive secondary metabolites used as lead compounds with medicinal importance. In this study, chemical investigation of the seawater-derived fungus Aspergillus sydowii SW9 led to the isolation and identification of one new quinazolinone alkaloid, 2-(4-hydroxybenzyl)-4-(3-acetyl)quinazolin-one (1), one new aromatic bisabolene-type sesquiterpenoid, (2) and one new chorismic acid analogue (3), as well as two known alkaloids (compounds 4 and 5). Their structures were determined by extensive 1D/2D NMR and mass spectrometric data, and the absolute configurations of 2 and 3 were assigned by the analysis of ECD spectra aided by quantum chemical computations. Compounds 1, 2, and 4 exhibited selective inhibitory activities against the human pathogenic bacteria Escherichia coli, Staphylococcus aureus, S. epidermidis, and Streptococcus pneumoniae, with MIC values ranging from 2.0 to 16 μg/mL.
Highlights
The fungus was identified by morphological observation and analysis of the Internal Transcribed Spacer (ITS) regions of its rDNA, whose sequence data were deposited at GenBank with the accession number MN696205
The mycelia were separated from the culture broth by filtration, and they were dried in the shade and exhaustively extracted with a mixture of ethyl alcohol and H2 O (95:5, v/v)
The organic extract was fractionated by vacuum liquid chromatography (VLC) on silica gel, eluting with different solvents of increasing polarity from petroleum ether (PE) to MeOH to yield nine fractions (Frs. 1–9), which were pooled based on TLC analysis
Summary
The species Aspergillus sydowii is generally characterized as a causative agent of aspergillosis of sea fan corals, based on morphological, physiological and nucleotide sequence analysis [1,2,3]. With the purpose of further searching for new antibiotic active metabolites from A. sydowii, continued our studies, and five compounds, including three previously undescribed compounds (1−3). We continued our studies, and five compounds, including three previously undescribed compounds along with two known alkaloids (4, 5) (Figure 1), were obtained and identified from the culture (1–3) along with two known alkaloids (4, 5) (Figure 1), were obtained and identified from the culture extract of A. sydowii SW9 Their structures were identified by extensive 1D/2D NMR and mass extract of A. sydowii SW9. All of these compounds were the analysis of ECD spectra aided by quantum chemical computations All of these compounds were tested for antimicrobial activities against four human pathogenic bacterial strains.
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