Iridoid glucosides of Paederota bonarota and the relationships between Paederota and Veronica

In a chemical investigation of the water-soluble compounds in Paederota bonarota, five known iridoid glucosides were isolated together with a compound with an 8,9-double bond, namely bonarotoside (10-O-benzoyl arborescosidic acid). The known iridoid glucosides were aucubin, catalpol and the 6-O-esters of catalpol: verproside, catalposide, amphicoside and veronicoside, compounds that are characteristic for many species of Veronica. The only other species in the genus Paederota, namely Paederota lutea contains an iridoid glucoside analogous to bonarotoside but with an additional arabinosyl moiety present. This common chemical attribute of Paederota distinguishes the genus from Veronica; it is in good agreement with the results from recent investigations of the phylogeny based on plastid DNA sequences of Veronica and its closest relatives, where Paederota is placed as a sister-group next to Veronica and not included in Veronica as previously suggested.