Unedoside derivatives in Nuxia and their biosynthesis

An investigation of two species of Nuxia showed that this genus is characterized by the presence of the eight-carbon iridoid glucoside unedoside and/or its derivatives. From N. floribunda unedoside, nuxioside (6- O -α- l -rhamnopyranosyl-unedoside) and 2″-acetyl-3″-cinnamoyl-nuxioside were isolated, while from N. oppositifolia 2″-acetyl-3″-benzoyl-nuxioside was obtained. Both plants contained verbascoside. The biosynthesis of unedoside in N. floribunda was investigated and deoxyloganic acid was found to be a precursor, similar to what was found for the eight-carbon iridoids in Thunbergia alata earlier investigated. The taxonomic position of Nuxia and Buddlejaceae is briefly discussed.