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

Abstract

Archaeological oak (Quercus sp.) wood samples, ranging from 16(th) C. AD to 6000 BP, were studied using flash pyrolysis-gas chromatography/mass spectrometry to obtain insight into angiosperm lignin degradation. The pyrolysates revealed evidence of a number of 3-methoxy-1,2-benzenediol derivatives, methoxycatechols, directly related to 2,6-dimethoxyphenol, syringyl, moieties which are characteristic building blocks of angiosperm lignin. Mass spectra and mass chromatograms of these compounds are reported. The finding of these characteristic pyrolysis products in well-preserved archaeological wood provides unequivocal evidence that demethylation of syringyl units occurs very early in wood degradation. It is highly likely that the absence of abundant 3-methoxy-1, 2-benzenediols in degrading plant materials containing angiosperm lignin relates to the lability of these newly formed moieties.

Lessons from Star Carr on the vulnerability of organic archaeological remains to environmental change

“…Samples were cleaned by heating to 290°C for 15 s in the presence of helium, followed by pyrolysis at 610°C for 15 s. The pyrolysis unit was coupled to a trace GC Ultra gas chromatograph (Thermo Fisher) fitted with a flame ionization detector and a fused silica capillary column (30 m × 0.25 mm) (Thermo Trace TR-5). The valve oven, transfer line, and GC inlet were held at 310°C, and the oven temperature was maintained at 50°C for 5 min; separation was achieved using a ramp rate of 4°C/min to 320°C, with a helium carrier gas at 2 mL/min (45). Retention times of key structural compounds were assigned based on published mass spectrometry data (45).…”

“…The valve oven, transfer line, and GC inlet were held at 310°C, and the oven temperature was maintained at 50°C for 5 min; separation was achieved using a ramp rate of 4°C/min to 320°C, with a helium carrier gas at 2 mL/min (45). Retention times of key structural compounds were assigned based on published mass spectrometry data (45).…”

A comparative thermogravimetric study of waterlogged archaeological and sound woods

“…Py-GC/MS was applied to the study of lignin and cellulose in order to investigate decay processes in aged woods [3,4]. CPMAS-NMR technique was applied to archaeological samples from the eleventh century excavation site at the Lake Paladru at Charavines (France) [5].…”

Molecular isotopic heterogeneity of fossil organic matter: implications for δ13Cbiomass and δ13Cpalaeoatmosphere proxies

“…van Bergen and . For a detailed description of the pyrolysis method used here, the reader is referred to van Bergen et al (2000). Identification of the various pyrolysis products (e.g., levoglucosan derived from cellulose, guaiacol and syringol products derived from lignin) was based on mass spectral data and retention time comparisons with reference samples and data reported in the literature (e.g., Saiz-Jimenez and de Leeuw, 1986;Pouwels et al, 1987Pouwels et al, , 1989van Bergen et al, 1996van Bergen et al, , 2000Stankiewicz et al, 1997).…”

“…5(a)] almost identical to that of on-line pyrolysates of modern oak wood samples (cf. van Bergen et al, 2000) indicating the presence of a well-preserved lignin-cellulose complex. In contrast, the pyrolysate of sample A2 [ Fig.…”