Biosynthetic pathway of β-thujaplicin in the Cupressus lusitanica cell culture

The biosynthesis pathway of beta-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-C-14]geraniol into beta-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 beta-thujaplicin are proposed, based on the NMR analysis of beta-thujaplicin biosynthesized in C. lusitanica cells from [1-C-13]-, 12-C-13]- and [U-C-13]-glucose. beta-Thujaplicin tvas 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 beta-thujaplicin via the limonane type skeleton, which is a common intermediate of cyclic monoterpene.