Phenol phlorotannins

Very little information exists on the phenolic protein-conplexing resins, except for that on creosote bush and sane arctic plants. In contrast to condensed tannins and hydrolyzable tannins, these are typically ether-soluble compounds this may allow their entry into the body across cell membranes, and thios give them the potential for action outside the gut lumen. Reports for animals consuming seaweed indicate that astringent protein-precipitating substances (presumably phlorotannins), are potentially important in marine plant-herbivore interactions. 

In total for seaweeds, it appears that the CNB hypothesis correctly predicted the responses of phlorotannins (three of three species157-181 184), but not of terpenes (zero of two species181185). Similarly, terrestrial ecologists have also found that the CNB hypothesis appears to predict the responses of phenolic compounds better than for other C-based secondary metabolites.176 177... 

One pattern that appears to be consistent with RAM is that immobile phlorotannins are often present at much higher concentrations (typically 0 to 18% dry mass) than immobile defenses (0 to 2% dry mass).111 Recent evidence suggests that turnover of phlorotannins is relatively slow, and that less than 1% of photosynthate from three brown seaweeds is allocated to maintain polyphenolic concentrations of 3 to 5%.69 Those authors calculated that the phenolic pool would turnover in 120 to 260 days, depending on the species, which is considerably more than the 32 to 110 days calculated in other studies.69 No comparable data are available for mobile secondary metabolites from seaweeds. 

Covalent bonds between oxidized phenolics and proteins were shown to be more likely to form at high pH since phenolics are more readily oxidized at high pH. This was particularly true with basic proteins and less so with acidic proteins.124163164 Because precipitation of phlorotannin-protein complexes was independent of temperature, hydrophobic forces were not considered likely to be important in their formation.124 164 These studies suggest that, although phlorotannin structure is important, at least part of the variation in sensitivity to dietary tannins is due to variation in herbivore gut chemistry. 

Connan, S. and Stengel, D. B. (2011). Impacts of ambient salinity and copper on brown algae 2. Interactive effects on phenolic pool and assessment of metal binding capacity of phlorotannin. Aquat. Toxicol. 104,1-13. 

The most important seaweed derived phenolic phytochemicals are phlorotannin polyphenols, which are uniquely found only in brown seaweeds [96], Phlorotannins are polymers which contain phloroglucinol as their monomeric component, and they are termed phlorotaimins since phloroglucinol is a common monomer unit [96]. As most tannins, similarly phlorotannins have the potential for cardiovascular disease management through an increase of HDL cholesterol and prevention of atherosclerosis [136-140], However, many recent reports have indicated more unique potential health benefits of phlorotaimins for a wide variety of diseases. A study by Li et al. [141] revealed that E. cava contains plenty of phlorotannin derivatives with interesting bioactivities. Chemical composition and antioxidant activity studies on E. cava showed that the major phlorotannins present are phloroglucinol, eckol. 

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