Comparative Flavonoid Chemistry of Hebe and Leonohebe (Plantaginaceae): Independent Characters For Taxonomic Studies

Abstract

A taxonomic revision of Hebe and Leonohebe in New Zealand has been carried out involving studies of both plant morphology and flavonoid chemistry and this thesis summarises the composition and taxonomic distribution of leaf flavonoids in the two genera. It describes the flavonoid glycosides encountered in a survey of c. 700 samples (from throughout the two genera), and outlines the distribution of flavonoids in species of "Buxifoliatae", "Flagriformes", "Appertae", large-leaved "Occlusae", small-leaved "Occlusae", "Grandiflorae", "Connatae", "Subcarnosae", and "Subdistichae" (informal infrageneric groups of Hebe) and in Leonohebe. Also included are seven putative hybrid samples. The structures of 83 of the most commonly occurring flavonoids are identified (or tentatively identified); a further 32 unidentified or partly identified flavonoids that are generally less common, are also recorded. Nonmetric multidimensional scaling analysis was carried out on the acquired flavonoid dataset. The large number of samples involved necessitated that this analysis be carried out separately on Leonohebe and each infrageneric group in Hebe. Most species, in each of the informal infrageneric groups of Hebe and Leonohebe, can be distinguished by their flavonoid profiles, generally through possession of unique combinations of compounds. Although some flavonoid compounds were restricted to a single infrageneric group, no flavonoid was found to distinguish all members of that group from any other. The degree of flavonoid profile variation of each species differed from species to species. Flavonoid profiles from a limited number of species were either collected at different times of the year or one or more samples from cultivated plants were taken as well as those from wild plants. Examination of these results suggests that flavonoid profile variation is not greatly influenced qualitatively by either season or ecological conditions.