25th International Meeting on Organic Geochemistry IMOG 2011

O-01
Extractive and structural phenolic compounds in a Neolithic
leather from the Swiss Alps
Jorge E. Spangenberg 1 , Albert Hafner 2
1 Institute of Mineralogy and Geochemistry, University of Lausanne, Lausanne, Switzerland, 2 Archaeological
Service of the Canton Bern, Bern, Switzerland (corresponding author:Jorge.Spangenberg@unil.ch)
Archaeological finds of leather are rare. If preserved,
the leather has naturally been re-tanned at the
particular burial environment, such as an anoxic
acidic environment in peat bogs, saline environments
in salt mines, or polyphenol-rich mediums in wooden,
oakcoffins [1]. None of these archaeological finds can
be used to identify the prehistoric tanning methods.
Leather clothing of the iceman Ötzi from the
Hauslabjoch (3350-3300 cal BC) has, for the first
time, provided the possibility to determine such
methods without any secondary influence; but the
artifacts were swabbed with phenol soon after their
discovery, making such investigations impossible [2].
A late Neolithic leather legging (2914-2652 cal BC),
well-preserved in situ, frozen in ice and snow, under
anaerobic conditions, was recovered from the
Schnidejoch ice-patch (2750 m amsl) in the western
Swiss Alps. This material provides an unequalled
opportunity to study the methods used in curing skins.
An important amount of n-alkanoic acids, waxy nalkanes,
n-alkan-1-ols and phytosterols (β-sitosterol,
sitostanol), and a biomarker of conifers (nonacosan-
10-ol) in the lipids extracted from the legging leather
(made from the skin of a domestic goat) indicate that
the Neolithic people were active in a subalpine,
coniferous forest [3].
In this study, a lipid-free aliquot of Schnidejoch leather
was subjected to a methanol/water extraction to
obtain the extractible phenolic compounds (fraction
A). The solid residue (mostly collagen) was acid
hydrolysed with methanol/HCl 6M to obtain the
structural phenols (fraction B), forming strong
complexes with macromolecules of collagen proteins.
The GC-MS traces of the TMS derivates of both
fractions show that the most abundant compounds
were n-alkanoic acids (C9-18) and short chain α, ω
alkandioic acids (C4-8) as residual lipids from animal
skin (Fig. 1). The presence of lignin monomers, such
as polyphenols and phenols containing keto and
carboxyl units is a diagnostic biomarker of vascular
plant tannins. These results provide direct evidence
for the use of aqueous extracts of higher plant
material, including oak bark for tanning leather in the
Alpine domain, 3d millennium BC.
Fig. 1. GC-MS TIC of the TMS derivates of fractions A and B
of Schnidejoch leather (see text).
References
[1] Groenman-van Waateringe, W. Kilian, M., Van
Londen, M. (1999) Antiquity 73, 884-890.
[2] Rollo, F. et al. (2000) American Journal of Physical
Anthropology 111, 211-219.
[3] Spangenberg, J.E. et al. (2010) Journal of
Archaeological Science 37, 1851-1865.
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