Phlorotannins structures

Table 11.2 Examples of the Six Brown Algal Phlorotannin Structural Types 107...

These apparent conflicts can be at least partially resolved by recognizing two factors (1) phlorotannins are not homogeneous in their structures (i.e., phlorotannin size34 70 119 120 156 and phlorotannin structural characteristics124 157) and thus affect herbivores differently, and (2) herbivore gut environments are not uniform, so that differences, including herbivore nutritional and physiological constraints, may be critical factors driving herbivore responses to phlorotannins 25,33,35,44,49,120,158-165... 

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. 

Van Altena, I.A. and Steinberg, P.D., Are differences in the responses between North American and Australasian marine herbivores to phlorotannins due to differences in phlorotannin structure , Bio-chem. Syst. Ecol., 20, 493, 1992. 

Pavia H, Cervin G, Lindgren A, Aberg P (1997) Effects of UV-B radiation and simulated herbivory on phlorotannins in the brown alga Ascophyllum nodosum. Mar Ecol Prog Ser 157 139-146 Pawlik JR (1993) Marine invertebrate chemical defenses. Chem Rev 93 1911-1922 Pettit GR, Kamano Y, Herald CL, Tuinman AA, Boettner FE, Kizu H, Schmidt JM, Baczynskyj L, Tomer KB, Bontems RJ (1987) The isolation and structure of a remarkable marine animal antineoplastic constituent dolastatin 10. J Am Chem Soc 109 6883-6885 Pfander H, Stoll H (1991) Terpenoid glycosides. Nat Prod Rep 8 69-95... 

The isopod I. baltica is adapted to use F. vesiculosus as food as shown by its capability to grow and reproduce when fed with this alga alone. I. baltica prefers F. vesiculosus as a structural host and feeds readily on it. However, F. vesiculosus is not the best single-host diet species growth of this herbivore on a sole F. vesiculosus diet was inferior to many other hosts and to a mixed diet (Jormalainen et al. 2001 Hemmi and Jormalainen 2004a). Phlorotannins from F. vesiculosus were harmful to the performance of this herbivore Increasing concentrations of phlorotannins in extracts from F. vesiculosus decreased both the total... 

In brown algae, phlorotannins are localized in specialized bodies called physodes (Ragan 1976). Shifting the experimental approach, from chemical assays of total phlorotannin concentration to microscopic methods that describe physode transport and establish the timeframes at which phlorotannins accumulate in response to abiotic or biotic stimuli, has provided new insight into the understanding of phlorotannin production and function. It is known that physodes are derived from the endoplasmic reticulum (ER) and Golgi of the cell (Schoenwaelder and Clayton 2000). It appears that physodes are transferred across the cytosol and incorporated into the cell wall, where the phlorotannins are assumed to have a structural role and thus be involved in primary metabolism (Schoenwaelder and Clayton 2000 Arnold and Targett 2003). 

Figure 11.3.10 General structures of (A) condensed tannins (n indicates number of subunits), (B) hydrolyzable tannins, and (C) phlorotannins. Chiral centers indicated by asterisks. G, galloyl. 

Antarctic brown macroalgae are also reported to elaborate phlorotannins (polyphenolics)65 66 which, in several temperate and tropical phaeophytes,13 are known to have antifeedant effects. However, the chemical structure and the ecological role of phlorotannins in Antarctic brown macroalgae still remain to be established. 

Terpenes and phlorotannins are two structural classes of secondary metabolites that are particularly important in mediating chemical interactions between marine plants and herbivores. Terpenes are commonly found in tropical macroalgae such as members of the Dictyotales (Phaeophyta) and... 

FIGURE 8.1 Structures of phlorotannins isolated from marine brown algae. 

FIGURE 10.1 Phlorotannins derived from brown seaweeds and their chemical structures. 

FIG. 33.2 Structures of phlorotannins from Ecklonia cava (1 dieckol 2 l-(3, 5 -dihy-droxyphenoxy)-7-(2",4",6"-trihydroxyphenoxy)-2,4,9-trihydroxydibenzo-l,4-dioxin). 

Fucodiphlorethol G (Fig. 33.3), a new compoimd isolated from the methanol extract of E. cava, a brown alga, collected offshore in Jeju Island by Ham et al. (2007). By the examination of and NMR data, it was foimd that the structure of the compoimd is similar to that of trimeric phlorotannin triphlorethol-A (Fig. 33.3). Although these studies evidenced that these compoimds can stimulate osteoblast differentiation at various stages, there is no clear demonstration of whether the phlorotannin compound, Fucodiphlorethol G, has direct effect on osteoblast differentiation. 

FIG. 33.3 Structure of phlorotannin from Ecklonia cava (1 fucodiphlorethol G 3 triphlorethol-A). 

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