Mechanism of iridane skeleton formation in the biosynthesis of iridoid glucosides in Gardenia jasminoides cell cultures.

Administration of 13C-labeled acyclic monoterpenes to Gardenia jasminoides f. grandiflora suspension cultures in various combinations demonstrated that the iridoid glucosides of the suspension cultures are biosynthesized through cyclization of 10-oxocitral (5) to the iridodial cation (17) followed by randomization of the carbon atoms 3 and 11. Additionally, the possibility of 10-hydroxycitronellol (12) and 9, 10-dihydroxycitronellol (13) serving as an intermediate was disproved.