Artemisia absinthium L., commonly known as wormwood, is a well-known medicinal plant with monographs in
several pharmacopoeas (e.g. Ph.Eur.). The aerial parts are used to treat anorexia
and indigestion. Sesquiterpene lactones e.g. absinthin, a dimer guaianolide, and the
monomer artabsin account for the bitter taste of this plant. Absinthin is also regarded
as marker substance to confirm the authenticity of wormwood.
In weak acidic medium absinthin is unstable and isomerizes into anabsinthin [1]. Older
literature describes absinthin as a glucoside, being decomposed by hydrolysis into
sugar, a liquid and a resinous compound [2]. To determine the stability of the bitter
substance, the degradation behaviour of absinthin was investigated under different
stress conditions (hydrolytic, oxidative, photolytic and thermal). An aqueous ethanol
solution of absinthin was found to be stable for up to 6 months (recovery rate by
HPLC analysis ≥95%). This was also the case when the solid compound was kept in the
refrigerator at -35°C. In contrast, the colourless needles, when stored in an exsiccator
at 25°C and exposed to light, turned yellow. In total, 3 decomposition compounds were
detected by LC/MS and LC-SPE-NMR, and identified as dimeric sesquiterpene lactones.
The major degradation product was anabsinthin, which is not only formed in acidic
medium, but also under acid-free conditions [1].
Acknowledgemenst: This work was financially supported by Bionorica research GmbH,
6020 Innsbruck, Austria
References: [1] Hänsel, R. and Sticher, O. (2007) Pharmakognosie – Phytopharmazie, 8. Auflage,
Springer Verlag, Heidelberg.
[2] Senger, O. (1892)J. Chem. Soc. 62:1240–1241.
