Abstract
Salterns, one of the most extreme natural hypersaline environments, are a rich source of halophilic and halotolerant microorganisms, but they remain largely underexplored ecological niches in the discovery of bioactive secondary metabolites. In continued efforts to investigate the metabolic potential of microbial populations from chemically underexplored sites, three new lipopeptides named iturin F1, iturin F2 and iturin A9 (1–3), along with iturin A8 (4), were isolated from Bacillus sp. KCB14S006 derived from a saltern. The structures of the isolated compounds were established by 1D-, 2D-NMR and HR-ESIMS, and their absolute configurations were determined by applying advanced Marfey’s method and CD spectroscopy. All isolates exhibited significant antifungal activities against various pathogenic fungi and moderate cytotoxic activities toward HeLa and srcts-NRK cell lines. Moreover, in an in vitro enzymatic assay, compound 4 showed a significant inhibitory activity against indoleamine 2,3-dioxygenase.
Highlights
Bacillus lipopeptides, represented by three classes, namely the iturins, surfactins and fengycins, have been widely studied for their effective antibacterial or antifungal activities [1]
A liquid chromatography-mass spectrometry (LC-MS) was performed using an LTQ XL linear ion trap (Thermo Scientific, Rockford, IL, USA) equipped with an electrospray ionization (ESI) source that was coupled to a rapid separation LC (RSLC; ultimate 3000, Thermo Scientific) system (ESI-LC-MS)
KCB14S006 obtained from salterns has led to the isolation of three new iturin class lipopeptides (1–3), along with one known metabolite, iturin A8 (4)
Summary
Bacillus lipopeptides, represented by three classes, namely the iturins, surfactins and fengycins, have been widely studied for their effective antibacterial or antifungal activities [1]. Iturins, which possess a heptapeptide backbone connected to a C13 to C17 β-amino fatty acid chain, exhibit strong in vitro fungitoxicity through the formation of ion-conducting pores on fungal membranes [1,2]. They exhibit structural heterogeneity at the amino acid residues as well as in their length and branching of the fatty acid chain.
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