Compartmentalization of phenolic constituents in sphagnum

[E]-4-ethoxycarbonyl-3-(4′-hydroxyphenyl)-but-2-en-1-carboxylic acid (trans-sphagnum acid ethyl ester) and p-hydroxyacetophenone were isolated from ethanolic extracts of Sphagnum magellanicum cell walls and [Z]-3-(4′-hydroxyphenyl)-pent-2-en-1,5-dicarboxylic acid (cis-sphagnum acid) from irradiated trans-sphagnum acid solutions. The structures of these compounds were elucidated by means of NMR spectroscopy. Compartmentalization studies revealed that the main part of detectable sphagnum acid is buffer-soluble, as well as in Sphagnum collected from natural sites and in Sphagnum cultivated in bioreactors. Cultivating Sphagnum species in bioreactors under axenic conditions leads to an enhancement of the buffer-soluble part of all analysed phenolics with a concomitant decrease of their cell wall-bound amount. Sphagnum acid, sphagnum acid ethyl ester, hydroxybutenolide, p-hydroxybenzoic acid, p-coumaric acid and t-cinnamic acid are also excreted to a remarkable extent into the effluent culture media of S. fallax and S. cuspidatum. Specific compartments for the storage of endogenous free water-soluble phenolics are postulated.