Leaf surface flavonoids of Chrysothamnus

Twenty-six flavonoid aglycones have been identified from eight plants covering three species of Chrysothamnus that were collected in eastern Oregon. The flavonoids were identified by NMR spectroscopy, tandem mass spectrometry and co-TLC with authentic markers. Chrysothamnus nauseosus yielded methyl ethers of apigenin, isoscutellarein, luteolin, kaempferol, herbacetin and quercetin. O-Methylated kaempferol and quercetin derivatives were isolated from the leaf exudate of C. humilis. The flavonoid chemistry of C. viscidiflorus was found different from the other two species by the presence of methyl ethers of quercetin, eriodictyol and taxifolin-3-acetate. Although the flavonoid profiles proved of diagnostic value at the species level, they provided little further evidence in favour of inclusion of Chrysothamnus into Ericameria as proposed earlier on the basis of morphological similarities. (C) 1999 Elsevier Science Ltd. All rights reserved.