Biosynthetic Pathway of β-Thujaplicin in the Cupressus lusitanica Cell Culture

The biosynthesis pathway of β-thujaplicin,which has a unique conjugated seven-membered ring structure, was investigated using the Cupressus lusitanica cell culture. We also examined a transformation of the carbon skeleton during its biosynthesis. Incorporation of [10-14C] geraniol into β-thujaplicin in the cell culture revealed that this compound was biosynthesized via geranylpyrophosphate (GPP) and hence is a monoterpenoid. The biosynthesis pathway from glucose to GPP and a skeletal rearrangement of GPP to β-thujaplicin are proposed, based on the NMR analysis of β-thujaplicin biosynthesized in C. lusitanica cells from [1-13C]-, [2-13C]- and [U-13C]-glucose. β-Thujaplicin was produced in the C. lusitanica cell from GPP, which was almost solely produced through the GAP/pyruvate pathway; contribution of the classical mevalonate pathway must be negligible, contrary to our previous conclusion. In addition, it was assumed that GPP was transformed to β-thujaplicin via the limonane type skeleton, which is a common intermediate of cyclic monoterpene.