Chamaejasnoids A-E, a 2,3-seco-guaiane sesquiterpenoid with a 5/6/7 bridged ring system and related metabolites from Stellera chamaejasme L.

Sixteen guaiane-type sesquiterpenoids were isolated from Stellera chamaejasme L. Among them, chamaejasnoids A-F (1-5) are new compounds. 1 represents the first example of 2,3-seco-guaiane sesquiterpenoid with a 5/6/7 bridged ring system. 2 is a unique 2-nor-guaiane sesquiterpenoid. A plausible biosynthetic pathway for 1 was proposed, involving a Baeyer-Villiger oxidation and a non-enzymatic intramolecular transesterification. 5 exhibited a selective cytotoxicity against HCT8 cell line with an IC50 of 11.82 ± 2.89 µM.

Characterization of a Sesquiterpene Synthase Catalyzing Formation of Cedrol and Two Diastereoisomers of Tricho-Acorenol from Euphorbia fischeriana.

A sesquiterpene synthase gene was identified from the transcriptome of Euphorbia fischeriana Steud, and the function of its product EfTPS12 was characterized by in vitro biochemical experiments and synthetic biology approaches. EfTPS12 catalyzed conversion of farnesyl diphosphate into three products, including cedrol (1) and eupho-acorenols A (2) and B (3) (two diastereoisomers of tricho-acorenol), thereby being named EfCAS herein. The structures of 2 and 3 were determined by spectroscopic methods and comparison of experimental and calculated electronic circular dichroism spectra. EfCAS is the first example of a plant-derived sesquiterpene synthase that is capable of synthesizing acorane-type alcohols. This study also documents that synthetic biology approaches enable large-scale preparation of volatile terpenes and thereby substantially facilitate characterization of corresponding terpene synthases and elucidation of the structures of their products.