Betulin-related esters from birch bark tar: Identification, origin and archaeological significance

Abstract

Birch bark tar, an organic material frequently encountered during archaeological excavations, has been identified from its lipid composition on the cracks of a ceramic dated to the late Neolithic. Lipids of this black substance were dominated by a characteristic triterpenoid assemblage of lupane-related triterpenoids from birch bark together with their thermal degradation products formed during preparation of the tar. Among the latter, four main series of unusual triterpenoid esters have been detected and were postulated to correspond to esters of D 2 -betulin and D 2dihydrobetulin based on their mass spectra and hydrolysis experiments.Their conclusive identification has been achieved by synthesis of reference compounds. These compounds most likely originate from the esterification between triterpenoid alcohols related to betulin and fatty acids from suberin formed upon heating of birch bark tar. They could be considered as markers of intense heating during birch bark tar preparation using the "single pot" procedure.

Classification of archaeological adhesives from Eastern Europe and Urals by ATR‐FT‐IR spectroscopy and chemometric analysis

“…The major components identified in these nine samples are presented in Table 2, with all the detailed results available in Table S4. Among them, four archaeological samples (Shigir (27), Shigir (44), Veretye I (51), and Veretye I (56)) were proved to contain mainly birch bark tar, as evidenced by the presence of molecular biomarkers (such as betulin and lupeol and their derivatives) (Aveling & Heron, 1998;Morandi et al, 2018; Perthuison et al, 2020); thus, these samples could be used as birch bark tar reference materials for future spectral interpretation and chemometric analysis.…”

“…The terpenoid compounds identified in samples were assigned to biomarkers of wood tars from betulaceae and pinaceae . The triterpenoids with lupane skeleton were detected in significant amounts in all samples but one (Stanovoye 4 (90)): biomarkers of birch bark tar, such as, lupeol, lupenone, betulin, betulin aldehyde, oleanic acid, lanostane, and their derivatives (Perthuison et al, 2020; Regert et al, 2006). Thus we can conclude that in most of the cases we have clear tendency toward the dominance of birch bark tar biomarkers (betulin derivatives), with sometimes additional small inclusions of coniferous tree resin in the samples analyzed with GC–MS.…”

“…Orsini et al analyzed fresh and archaeological birch bark tar with GC-MS proving hydroxyl long-chain α,ω-diacids and ω-hydroxyacids with unsaturation, epoxy groups, and vic-diol groups to be the dominant component of fresh birch bark tar (Orsini et al, 2015). The identification of large amounts of aromatic compounds including vanillin, ferulic acid, and different terpenoid compounds further confirmed the resinous composition of these samples (Morandi et al, 2018;Perthuison et al, 2020). The terpenoid compounds identified in samples were assigned to biomarkers of wood tars from betulaceae and pinaceae.…”

Oxidative Functionalization of Trinor-18α-olean-17(22)-ene Derivatives. Annulation of the E-Ring by an Intramolecular Aldol Reaction

“…Its wood has had important historical and cultural significance since ancient times. 1 , 2 Nowadays, birch wood is widely used in the paper industry. The outer part of birch bark (the waste generated during paper production) is an extremely rich source of lupane-type triterpenes, mostly betulin ( 1 , Scheme 1 ), which are isolated in appreciable amounts (up to 30% of dry mass).…”

“…Birch is a hardwood tree of the genus Betula widespread in the Northern Hemisphere, particularly in areas of temperate and boreal climates. Its wood has had important historical and cultural significance since ancient times. , Nowadays, birch wood is widely used in the paper industry. The outer part of birch bark (the waste generated during paper production) is an extremely rich source of lupane-type triterpenes, mostly betulin ( 1 , Scheme ), which are isolated in appreciable amounts (up to 30% of dry mass). , Betulin has interesting biological properties, including antiviral and antitumor activities. − Lupane triterpenoids have also been used as intermediates in the synthesis of triterpenoids employed for biological studies. − …”