CHEMISTRY OF GLANDULAR TRICHOMES IN HYMENOXYS AND RELATED GENERA

All currently recognized taxa from the genera Amblyolepis (one species ), Dugaldia (three species), Hymenoxys (22 taxa in 21 species), Macdou galia (one species), Plateilema (one species), Plummera (two species) and Tetraneuris (15 taxa in eight species) were examined for chemical constituents accumulated in capitate glandular trichomes. Fifty-nine h igh pressure liquid chromatography (HPLC) peaks were detected, over 70 % of which could be tentatively assigned to known compounds of the ses quiterpene lactone, monoterpene and inositol types. This is the first report of sesquiterpene lactone glycosides, monoterpene glycosides and a myoinositol derivative in capitate glandular trichomes. Apart from Amblyolepis and Plateilema, which did not afford analyzable glandular trichomes, sesquiterpene lactones of the pseudoguaianolide type were p resent in all species, and guaianolides were found in all but two, Hym enoxys anthemoides and H. chrysanthemoides. Compound patterns of the H ymenoxys, Plummera, Dugaldia and Macdougalia species were very similar to one another, but they differed from those of Hymenoxys texana and all taxa of Tetraneuris, which lacked modified pseudoguaianolides (sec ohelenanolides), but contained monoterpene glycosides. Taxonomic impli cations of compound patterns in the species examined includes: (1) inc orporation of Dugaldia, Plummera and Macdougalia into a broader concep t of Hymenoxys; and (2) recognition of Tetraneuris as a distinct genus . Hymenoxys texana requires further investigation since its morphology is typical of Hymenoxys, but its chemistry is typical of Tetraneuris.