Sesquiterpenoids, biosynthesised in higher plants, are found to have a wide range of biological properties, some of which are valuable to humans. Especially sesquiterpene lactones are known for their anti-malarial, anti-cancer and anti-microbial properties. Sesquiterpenoids of pharmaceutical value have been investigated in several plant species and families including Apiaceae.

This PhD thesis was focused on sesquiterpenoids from the genus Thapsia, Apiaceae. Thapsia is distributed throughout the Mediterranean region where they grow as weeds. The sesquiterpenoid thapsigargin produced by Thapsia garganica is of particular interest since it has shown promising results in clinical trials against solid cancer tumours.
Transcriptome analysis of Thapsia garganica has now revealed the first two biosynthetic steps towards thapsigargin. These steps includes a sesquiterpene synthase and a cytochrome P450 and results in formation of a precursor sesquiterpene lactone.

Investigation of sesquiterpenoid biosynthesis in the related species Thapsia laciniata has shown a different sesquiterpenoid profile and a diverged evolution compared to Thapsia garganica.