Marine Polyphenols

A kelp bed looks calm from the shore. Underneath, the chemistry is anything but: brown algae manufacture polymers of phloroglucinol as defence against grazers, microbes and ultraviolet radiation, and they store them at concentrations that no land plant comes close to. Those polymers — phlorotannins, and the smaller eckol-type molecules built from the same building block — are the most commercially interesting family in marine phenolic chemistry, and they are what this page is about.

Eata Marisource supplies that chemistry in whichever state your work needs it: crude aqueous extracts for screening panels, ethanol-standardised powders for formulation, ethyl acetate fractions enriched in oligomeric phlorotannins, and purified single compounds for calibration and mechanism studies. Everything below can be adjusted — solvent residue limits, phenolic cut-off, carrier, particle size — and the final section of this page explains how.

The Chemistry We Supply

Phlorotannins are oligomers and polymers of phloroglucinol (1,3,5-trihydroxybenzene) linked through aryl and ether bonds, with the eckol family distinguished by a dibenzo-1,4-dioxin bridge. Reported molecular masses span an extraordinary range — roughly 126 Da for the monomer up to 650 kDa for the heavily polymerised, cell-wall-bound fraction — and the soluble pool held in intracellular physodes can account for a substantial share of the dried alga. That structural spread is the whole reason two extracts of the same species can behave differently in your assay, and it is why we characterise the distribution rather than just a single number.

Olive-brown polyphenol powder, standardised on total phenolic content, shown in a shallow dish.

Sourcing: Species, Season and Drying

Content is not a fixed property of a species. Phlorotannin levels shift with season, tissue type, depth and reproductive state — published work on Ecklonia cava, for example, finds mature thalli carrying around 1.8 mg/g dry tissue of dieckol and roughly 1.5 mg/g of phlorofucofuroeckol-A, with blade tissue consistently richer than stipe or holdfast. We buy against specification, not against a species name alone, and we test every incoming lot before it enters production.

Dried brown-alga thallus pieces with air bladders — the raw material behind our phlorotannin grades.

Post-harvest handling turns out to matter just as much as where the biomass came from. Comparative work on drying regimes reports that shade- and freeze-dried material releases close to 90% of its dieckol and phlorofucofuroeckol-A relative to lyophilised reference tissue, whereas sun- and oven-dried material gives back only around 60%. Washing in fresh water and blanching are worse still. Our supply agreements specify shade drying or controlled low-temperature drying, and we audit that step rather than assume it.

Extraction and Fractionation

Most of our volume runs on aqueous ethanol — typically 60–80% ethanol at a solid-to-liquid ratio near 1:10, held between 50 and 60 °C — because it recovers both oligomeric and mid-range phlorotannins without dragging in the alginate and salt load that plain water does. Where a customer wants the polar, high-molecular-weight end, we run hot-water extraction instead and accept the carbohydrate burden, then remove it downstream.

Liquid–liquid fractionation in progress: a dark organic layer sitting above a pale aqueous layer.

The enrichment step that follows is usually a liquid–liquid split, most often into ethyl acetate, which strips the oligomeric phlorotannins away from sugars, salts and most pigments. Published comparisons show how effective that step can be: an ethyl acetate fraction of Ecklonia stolonifera carries roughly 30 mg/g of dieckol against microgram-level figures in the parent ethanol extract. From there, resin adsorption or centrifugal partition chromatography takes the fraction to the purity your application needs.

Purification to Single Compounds

Isolating individual phlorotannins used to mean repeated size-exclusion passes followed by preparative reversed-phase runs. Centrifugal partition chromatography has shortened that considerably: with a two-phase system of n-hexane, ethyl acetate, methanol and water, dieckol and phlorofucofuroeckol-A can be taken from an ethyl acetate fraction to 90% purity or better in a single step. We run both approaches and choose between them on the target and the quantity.

Analytical chromatography system with autosampler carousel, used for single-compound quantification.

Structural confirmation is where most suppliers stop and we do not. Low-molecular-weight phlorotannins tend to elute as poorly resolved humps on reversed-phase columns, so identity rests on diode-array data plus mass spectrometry — HPLC-DAD-ESI/MSn for routine work, UPLC-QTOF where isomeric complexity is in question. Expect a chromatogram trace with every purified single, not a single purity percentage.

How the Numbers Are Measured

Two numbers can both be called “total phenolic content” and differ by a factor of thirty, which is why the method belongs on the specification. The Folin–Ciocalteu reagent reads at about 760 nm and responds to almost anything reducing in the matrix — sugars, proteins, thiols, even Fe(II) and iodide — so it overstates phlorotannins badly. The DMBA assay reacts specifically with 1,3- and 1,3,5-substituted phenols at around 510 nm, is far more selective, and can undercount branched structures in return. On one published Sargassum sample, Folin–Ciocalteu returned close to 149 mg phloroglucinol equivalents per gram while DMBA returned a little over 5 — the same seaweed, two defensible answers.

Microplate wells showing the graded colour response of a total phenolic assay.

Where These Fractions Go

Phenolics bind proteins. That single property — covalent and non-covalent, through hydrophobic contact and hydrogen bonding — explains most of the industrial interest in this family, and it is the thread running through the applications below.

• Delivery systems — phlorotannins cross-link proteins and polysaccharides, stiffening microcapsule shells and tuning release behaviour in encapsulation research.
• Feed and preservation — seaweed phenolics are studied as marine-origin antioxidants that slow lipid oxidation in feeds, and their membrane-disrupting activity is being assessed against Vibrio and Aeromonas species.
• Cosmetic and enzyme research — tyrosinase, elastase and hyaluronidase inhibition assays are the standard entry point, and purified singles give cleaner dose responses than crude extracts.
• Metal interaction — the dense hydroxyl array chelates metal ions, which is why these fractions appear in anticorrosion, wastewater and green nanoparticle synthesis work.
• Colour and tanning — polyphenol–protein complexation darkens and stabilises leather, wool and dye baths, and marine phenolics bring a different hue and kinetics profile than terrestrial tannins.
• Analytical and reference use — eckol, dieckol and phlorofucofuroeckol-A as calibration standards for the HPLC and LC-MS methods described above.

Keeping Phenolics Intact

Phlorotannins oxidise readily once dry powder meets air and light; colour drift is usually the first sign that a specification is no longer true. We dry under reduced temperature, mill to a defined particle size, and pack in amber glass or foil-laminate with oxygen scavengers where the grade warrants it. Solutions are shipped cold with headspace minimised.

Amber glass vials of brown polyphenol solution prepared for stability and shipment checks.

On request we run accelerated and real-time stability under your own storage conditions and report colour, phenolic content and HPLC profile at each pull point — useful when the fraction is heading into a formulation whose matrix will accelerate or mask degradation.

Developed Around Your Specification

Most of what leaves our facility is a standard grade; the interesting work is usually the rest. We take on custom phenolic targets, alternative solvent systems and residue limits, defined molecular-weight windows rather than single purity numbers, carrier changes, blends of two or more phenolic families, and fraction libraries built around a customer's own screening cascade. Prototype quantities are produced under the same analytical regime as catalogued grades, so a custom lot arrives with a data pack you can actually use.

If you already know the molecule and only need a supply route, tell us. If you know the application and not the molecule, tell us that instead — the second conversation is often the more productive one.

For Research or Industrial Raw Materials, Not For Personal Medical Use!