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Profiling of the molecular weight and structural isomer abundance of macroalgae-derived phlorotannins.

Heffernan N, Brunton NP, FitzGerald RJ, Smyth TJ - Mar Drugs (2015)

Bottom Line: The majority of the low molecular weight (LMW) phlorotannins were found to have a molecular weight range equivalent to 4-12 monomers of phloroglucinol.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 Article: PubMed Central - PubMed

Affiliation: Food Biosciences Department, Teagasc Food Research Centre, Ashtown, Dublin 15, Ireland. dick.fitzgerald@ul.ie.

ABSTRACT
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.

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Total ion chromatogram (TIC) of reverse phase (RP) flash chromatography-enriched fractions of (a) Fucus serratus; (b) Fucus vesiculosus; (c) Himanthalia elongate; and (d) Cystoseira nodicaulis. Prominent peaks are labeled with retention time (on the left or on top) along with observed m/z (on the right or below the retention time).
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marinedrugs-13-00509-f001: Total ion chromatogram (TIC) of reverse phase (RP) flash chromatography-enriched fractions of (a) Fucus serratus; (b) Fucus vesiculosus; (c) Himanthalia elongate; and (d) Cystoseira nodicaulis. Prominent peaks are labeled with retention time (on the left or on top) along with observed m/z (on the right or below the retention time).

Mentions: Figure 1 displays a total ion chromatogram (TIC) of reversed-phase (RP) flash chromatography-enriched fractions of the four species under investigation, presenting the structural complexity of the isolated phlorotannins. The characterization of phlorotannins, which in theory could be generated by indiscriminate coupling during biosynthesis, is taxing due to the difficulty in separating complex isomeric mixtures with identical molecular weights and similar structures into individual compounds [37]. Due to the large numbers of isomers present at each level of DP (degree of polymerization) in particular species, it is unlikely that the isolation and subsequent characterization of their structure will be attainable in the near future. Individual structural elucidation of each phlorotannin present in the species investigated in this study would not be possible with current chromatographic techniques. A more feasible aim would be to investigate species containing complex isomeric mixtures by UPLC and mass spectrometric profiling, which has been limited to date [34,39].


Profiling of the molecular weight and structural isomer abundance of macroalgae-derived phlorotannins.

Heffernan N, Brunton NP, FitzGerald RJ, Smyth TJ - Mar Drugs (2015)

Total ion chromatogram (TIC) of reverse phase (RP) flash chromatography-enriched fractions of (a) Fucus serratus; (b) Fucus vesiculosus; (c) Himanthalia elongate; and (d) Cystoseira nodicaulis. Prominent peaks are labeled with retention time (on the left or on top) along with observed m/z (on the right or below the retention time).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4306949&req=5

marinedrugs-13-00509-f001: Total ion chromatogram (TIC) of reverse phase (RP) flash chromatography-enriched fractions of (a) Fucus serratus; (b) Fucus vesiculosus; (c) Himanthalia elongate; and (d) Cystoseira nodicaulis. Prominent peaks are labeled with retention time (on the left or on top) along with observed m/z (on the right or below the retention time).
Mentions: Figure 1 displays a total ion chromatogram (TIC) of reversed-phase (RP) flash chromatography-enriched fractions of the four species under investigation, presenting the structural complexity of the isolated phlorotannins. The characterization of phlorotannins, which in theory could be generated by indiscriminate coupling during biosynthesis, is taxing due to the difficulty in separating complex isomeric mixtures with identical molecular weights and similar structures into individual compounds [37]. Due to the large numbers of isomers present at each level of DP (degree of polymerization) in particular species, it is unlikely that the isolation and subsequent characterization of their structure will be attainable in the near future. Individual structural elucidation of each phlorotannin present in the species investigated in this study would not be possible with current chromatographic techniques. A more feasible aim would be to investigate species containing complex isomeric mixtures by UPLC and mass spectrometric profiling, which has been limited to date [34,39].

Bottom Line: The majority of the low molecular weight (LMW) phlorotannins were found to have a molecular weight range equivalent to 4-12 monomers of phloroglucinol.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 Article: PubMed Central - PubMed

Affiliation: Food Biosciences Department, Teagasc Food Research Centre, Ashtown, Dublin 15, Ireland. dick.fitzgerald@ul.ie.

ABSTRACT
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.

Show MeSH
Related in: MedlinePlus