Sphagnum acid and its decarboxylation product isopropenylphenol as biomarkers for fossilised sphagnum in peats

Sphagnum acid, a unique biomarker for Sphagnum mosses, can be traced by analytical pyrolysis mass spectrometric methods in handpicked leaves and stems isolated from peat deposits. Due to the thermolability of the compound, sphagnum acid decarboxylates under pyrolysis conditions to 4-isopropenylphenol or to 3-(4'-hydroxyphen-1-yl)-but-2-enoic acid methyl ester in the presence of tetramethylammoniumhydroxide (TMAH) reagent. Solvent, alkali and acid extracted Sphagnum cell walls also show these marker compounds pointing to an ether linkage of this phenolic acid to the biomatenal. Sphagnum acid is found to be preserved in Holocene (6000 BP) peatified leaves and stems of Sphagnum. A chemically bound 4-isopropenylphenol is demonstrated in Pleistocene (Eemian, 70 000 BP) Sphagnum leaves.