Turnover of hexitols in the marine macroalgaHimanthalia elongata(Phaeophyta, Fucales)

Abstract

'3C nuclear magnetic resonance spectroscopy (NMR) has been used to study the metabolic flux of carbon through the intracellular pools of the isomeric hexitols D-altritol and D-mannitol in Himanthalia elongata. Natural abundance ~3C NMR spectra of freshly collected plant material showed altritol as the dominant intracellular low-molecular-weight organic solute, with mannitol present at less than 20% of the altritol concentration. Plant material incubated in seawater medium with added *3C-enriched bicarbonate showed a rapid increase in the 13C signal due to mannitol, with an increase of more than 12-fold in under 48 h, in contrast to the altritol signal, which increased by approximately 2-fold over the same period. The intracellular mannitol signal decreased rapidly when *3C-enriched plant material was transferred to a non-enriched medium, while altritol showed a slower decline. These results are consistent with previous observations on the effects of salinity on the intracellular hexitol pools of H. elongata, suggesting that mannitol is more rapidly metabolised than altritol. Estimates of the half-time for tracer exchange support this view, with a half-time for the turnover of altritol ( > 400 h) which is an order of magnitude greater than that for mannitol turnover (~ 50 h).

Seaweeds as a Functional Ingredient for a Healthy Diet

“…Marine algae, because they live in an environment with a very high concentration of salts, need to accumulate solutes that allow to regulate the osmotic balance between their cells and the environment. Many ions such as sodium, chlorine, and potassium are involved in this process, but certain low molecular weight carbohydrates are also involved [38]. These include, for example, sucrose in green algae, alditols such as mannitol in brown and red algae [38], and hexitols such as digeneasides and fluorosides in red algae [39].…”

“…Many ions such as sodium, chlorine, and potassium are involved in this process, but certain low molecular weight carbohydrates are also involved [38]. These include, for example, sucrose in green algae, alditols such as mannitol in brown and red algae [38], and hexitols such as digeneasides and fluorosides in red algae [39]. In addition, the main low molecular weight carbohydrate present in many species of brown algae, especially in Laminaria and Ecklonia, is mannitol.…”