Evidence for demethylation of syringyl moieties in archaeological wood using pyrolysis-gas chromatography/mass spectrometry

Archaeological oak (Quercus sp,) wood samples, ranging from 16(th) C. AD to 6000 BP, were studied using flash pyrolysis-gas chromatography/mass spectr ometry to obtain insight into angiosperm lignin degradation. The pyrolysate s revealed evidence of a number of 3-methoxy-1,2-benzenediol derivatives, m ethoxycatechols, directly related to 2,6-dimethoxyphenol, syringyl, moietie s which are characteristic building blocks of angiosperm lignin. Mass spect ra and mass chromatograms of these compounds are reported. The finding of t hese characteristic pyrolysis products in well-preserved archaeological woo d provides unequivocal evidence that demethylation of syringyl units occurs very early in wood degradation. It is highly likely that the absence of ab undant 3-methoxy-1,2-benzenediols in degrading plant materials containing a ngiosperm lignin relates to the lability of these newly formed moieties, Co pyright (C) 2000 John Whey & Sons, Ltd.