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Iodinated Meroditerpenes from a Red Alga Callophycus sp.
journal contribution
posted on 2017-04-05, 00:00 authored by Serge Lavoie, David Brumley, Troy S. Alexander, Christine Jasmin, Franz A. Carranza, Kate Nelson, Cassandra L. Quave, Julia KubanekUnique iodine-containing meroditerpenes iodocallophycoic acid A
(1) and iodocallophycols A–D (2–5) were discovered from the Fijian red alga Callophycus sp. Because flexibility of the molecular skeleton impaired full
characterization of relative stereochemistries by NMR spectroscopy,
a DFT-based theoretical model was developed to derive relevant interproton
distances which were compared to those calculated from NOE measurements,
yielding the relative stereochemistries. The correct 2S,6S,7S,10S,14S enantiomers were then identified by comparison of theoretical
and experimental ECD spectra. Biological activities of these iodinated
and brominated meroditerpenes and additional new, related bromophycoic
acid F (6) and bromophycoic acid A methyl ester (7), were evaluated for relevant human disease targets. Iodocallophycoic
acid A (1) showed moderate antibiotic activity against
methicillin-resistant Staphylococcus aureus (MRSA)
and vancomycin-resistant Enterococcus faecium (VREF)
with MIC values of 1.4 and 2.2 μg mL–1, respectively.
It also potentiated the anti-MRSA activity of oxacillin in a synergistic
fashion, resulting in an 8-fold increase in oxacillin potency, for
a MIC of 16 μg mL–1.
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methicillin-resistant Staphylococcus aureusstereochemistrieBiological activitiesvancomycin-resistant Enterococcus faeciumdisease targetsmethyl esterbrominated meroditerpenesoxacillin potencyRed Alga Callophycus spVREFNOE measurementsantibiotic activityIodocallophycoic acidUnique iodine-containing meroditerpenes iodocallophycoic acidbromophycoic acid Fbromophycoic acidmLinterproton distancesECD spectraNMR spectroscopyalga Callophycus spMIC valuesanti-MRSA activity
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