Biosynthesis of lunularic acid—a dihydrostilbene endogenous growth inhibitor of liverworts

Incorporations of U- 14 C- l -phenylalanine, 1- 14 C-sodium acetate and 14 C-hydrangenol (IV) into lunularic acid (I) by the liverwort Lunularia cruciata are reported. The results show, that like other plant stilbene derivatives, lunularic acid can be biosynthesized by the phenylpropanoid-polymalonate pathway. The phenyldihydroisocoumarin, hydrangenol (IV), and/or its isomeric stilbene derivative, hydrangeic acid (VI), are probable intermediates in the biosynthesis of lunularic acid. Although no free or bound hydrangenol or hydrangeic acid could be detected in the liverwort they were found to co-occur with lunularic acid, in an acid labile bound form, in roots of Hydrangea macrophylla . A hypothesis for the photoperiodic control of liverwort growth by control of lunularic acid synthesis is presented.