Antibacterial Neurymenolides from the Fijian Red Alga Neurymenia fraxinifolia

Abstract

Two novel α-pyrone macrolides, neurymenolides A (1) and B (2), were isolated from the Fijian red alga Neurymenia fraxinifolia and characterized using a combination of NMR and mass spectral analyses. These molecules represent only the second example of α-pyrone macrolides, with 1 existing as interchanging atropisomers due to restricted rotation about the α-pyrone ring system. Neurymenolide A (1) displayed moderately potent activities against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecium (VREF).

Seaweed Allelopathy Against Coral: Surface Distribution of a Seaweed Secondary Metabolite by Imaging Mass Spectrometry

“…Accurate identification of compounds was confirmed by using a combination of methods including: comparison with known 1 H NMR spectra, retention time and peak shape by LC-MS and/or HPLC, and mass measurements using ESI-time-of-flight (TOF) MS accurate to 1 ppm in positive ion mode. For all of these methods, NMR chemical shifts and coupling constants and molecular ions measured by MS matched reported data for neurymenolide A (Stout et al, 2009)…”

“…Preliminary evaluations of both active fractions (chloroform and chloroform F4) were conducted by LC-MS before further purification. Retention times (not shown but compared to Stout et al, 2009) and m/z values (Fig. 3A) indicated the presence of neurymenolides in both fractions.…”

“…All active fractions contained the same prominent peaks: a pair of peaks relating to the interchangeable atropisomers of neurymenolide A followed immediately by a single peak of neurymenolide B (Stout et al, 2009). Accurate identification of compounds was confirmed by using a combination of methods including: comparison with known 1 H NMR spectra, retention time and peak shape by LC-MS and/or HPLC, and mass measurements using ESI-time-of-flight (TOF) MS accurate to 1 ppm in positive ion mode.…”

“…Fractions that decreased effective quantum yield were analyzed using highperformance liquid-chromatography mass-spectrometry (HPLC-MS) and normal-phase high-performance liquid chromatography (HPLC) as described inStout et al (2009). All active fractions contained the same prominent peaks: a pair of peaks relating to the interchangeable atropisomers of neurymenolide A followed immediately by a single peak of neurymenolide B (Stout et al, 2009).…”

“…This study confirms that direct contact with seaweeds can damage coral, that the majority of that damage is due to chemical rather than physical interactions, that the allelopathic metabolite is neurymenolide A, and that this compound occurs on the algal surface, allowing it to effectively transfer to and damage corals. Because neurymenolide A was first identified as an antibacterial natural product (Stout et al, 2009), this work also suggests multiple roles for deterrent compounds (Schmitt et al, 1995; Kubanek et al, 2002) located on biological surfaces where contact with multiple natural enemies (pathogens, competitors, biofoulers, consumers) will first occur, and suggests that these allelopathic metabolites could act by destabilizing the coral’s microbiome by suppressing beneficial microbes, enhancing detrimental ones, or both (Ritchie, 2006; Smith et al, 2006). …”