Abstract
The combination of LC-MS/MS based metabolomics approach and anti-MRSA activity-guided fractionation scheme was applied on the Gram-negative bacterium Aequorivita sp. isolated from shallow Antarctic sea sediment using a miniaturized culture chip technique. This methodology afforded the isolation of three new (1–3) and four known (4–7) N-terminal glycine- or serine-bearing iso-fatty acid amides esterified with another iso-fatty acid through their C-3 hydroxy groups. The chemical structures of the new compounds were elucidated using a set of spectroscopic (NMR, [α]D and FT-IR) and spectrometric (HRMS, HRMS/MS) methods. The aminolipids possessing an N-terminal glycine unit (1, 2, 4, 5) showed moderate in vitro antimicrobial activity against MRSA (IC50 values 22–145 μg/mL). This is the first in-depth chemistry and biological activity study performed on the microbial genus Aequorivita.
Highlights
The diversity of microbes on earth is enormous
The HRMS2 fragmentation pattern was most helpful in rapid identification of the chain length and unsaturation level of iso-fatty acyl moieties following the cleavage of the ester bond at C-3 (Figure S20)
The IC50 values observed for each compound were as follows: 1 (58 μg/mL), 2 (145 μg/mL), 4 (22 μg/mL) and 5 (93 μg/mL). These results indicate that the methylation of the N-terminal amino acid residue or the introduction of a double bond in the lower iso-fatty acyl chain diminishes or totally abolishes the antibiotic activity (IC50 > 200 μg/mL)
Summary
The diversity of microbes on earth is enormous. despite all the progress made in microbiology over more than 100 years, still only a little fraction (
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