Trinorlupeol: a major nonsterol triterpenoid in Arabidopsis.

We report the structure determination of 20,29,30-trinorlup-18-en-3beta-ol (trinorlupeol) and establish this novel C 27 metabolite as a major nonsterol triterpenoid in Arabidopsis thaliana. Trinorlupeol was concentrated in cuticular waxes, notably in the plant stem, floral buds, and seedpods, but not in leaves. Based on expression data and functional characterization of A. thaliana oxidosqualene cyclases, we propose that LUP1 is the cyclase responsible for trinorlupeol biosynthesis. Also described are two oxidized trinorlupeols and additional biosynthetic insights.