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Open AccessArticle

Profiling of the Molecular Weight and Structural Isomer Abundance of Macroalgae-Derived Phlorotannins

1
Food Biosciences Department, Teagasc Food Research Centre, Ashtown, Dublin 15, Ireland
2
Department of Life Science, University of Limerick, Limerick, Ireland
3
School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland
4
Department of Life Sciences, Institute of Technology Sligo, Sligo, Ireland
*
Author to whom correspondence should be addressed.
Academic Editor: Daniel Dias
Mar. Drugs 2015, 13(1), 509-528; https://doi.org/10.3390/md13010509
Received: 30 June 2014 / Accepted: 21 November 2014 / Published: 16 January 2015
(This article belongs to the Special Issue Metabolomics - Applications in Marine Natural Products Chemistry)
Phlorotannins are a group of complex polymers of phloroglucinol (1,3,5-trihydroxybenzene) unique to macroalgae. These phenolic compounds are integral structural components of the cell wall in brown algae, but also play many secondary ecological roles such as protection from UV radiation and defense against grazing. This study employed Ultra Performance Liquid Chromatography (UPLC) with tandem mass spectrometry to investigate isomeric complexity and observed differences in phlorotannins derived from macroalgae harvested off the Irish coast (Fucus serratus, Fucus vesiculosus, Himanthalia elongata and Cystoseira nodicaulis). Antioxidant activity and total phenolic content assays were used as an index for producing phlorotannin fractions, enriched using molecular weight cut-off dialysis with subsequent flash chromatography to profile phlorotannin isomers in these macroalgae. These fractions were profiled using UPLC-MS with multiple reaction monitoring (MRM) and the level of isomerization for specific molecular weight phlorotannins between 3 and 16 monomers were determined. The majority of the low molecular weight (LMW) phlorotannins were found to have a molecular weight range equivalent to 4–12 monomers of phloroglucinol. The level of isomerization within the individual macroalgal species differed, resulting in substantially different numbers of phlorotannin isomers for particular molecular weights. F. vesiculosus had the highest number of isomers of 61 at one specific molecular mass, corresponding to 12 phloroglucinol units (PGUs). These results highlight the complex nature of these extracts and emphasize the challenges involved in structural elucidation of these compounds. View Full-Text
Keywords: phlorotannins; metabolomic profiling; UPLC-MS/MS profiling; antioxidant activity; isomerization; brown macroalgae phlorotannins; metabolomic profiling; UPLC-MS/MS profiling; antioxidant activity; isomerization; brown macroalgae
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Heffernan, N.; Brunton, N.P.; FitzGerald, R.J.; Smyth, T.J. Profiling of the Molecular Weight and Structural Isomer Abundance of Macroalgae-Derived Phlorotannins. Mar. Drugs 2015, 13, 509-528.

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