Karin M. Valant-Vetschera

Chemodiversity of exudate flavonoids in some members of the Lamiaceae

Several newly studied species and further accessions of the Lamiaceae have been analyzed for their exudate flavonoid profiles. The principal compounds accumulated were flavones and their 6-methoxy derivatives, whereas flavonols were rarely encountered. The chemodiversity observed was relatively low, with only some 15 derivatives being found. The new data are discussed in relation to published data, and chemosystematic aspects are briefly addressed. Of the studied species, Salvia arizonica yielded only a rare diterpene quinone, demethylfruticulin A. Glandular hair diversification and different qualities of their secretions are briefly discussed.

Exudate flavonoids in species of Artemisia (Asteraceae—Anthemideae): new results and chemosystematic interpretation

Nine species belonging to various taxonomic units within the genus Artemisia were studied for their exudate flavonoid composition. In addition to 49 different flavones, flavonols, flavanones and dihydroflavonols, a coumarin and a phloroacetophenone were also found as exudate constituents. The majority of flavonoids exhibited 7,3′- or 7,4′-substitution, whereas 6-substitution was rather rare. Similarly, higher substituted derivatives were shown to be of rare occurrence in the species studied. Some aspects of chemosystematic relevance are shortly discussed, and the substitution trends of the various flavonoid groups are discussed in a biosynthetic context.

Leaf flavonoids of the Achillea Millefolium group part II: Distribution patterns of free aglycones in leaf exudates☆

Seventy-eight collections of species forming the Achillea millefolium group were studied for the aglycone composition of their leaf exudates. 6-Hydroxyflavones, 6-hydroxyflavonols and their methyl ethers predominate in the exudates in various combinations. Within the polyploid complex, the diploid taxa Achillea setacea and Achillea aspleniifolia appeared to be chemically well defined. Among the polyploids, little differentiation of major accumulation trends was observed. Infraspecific variability was low in most cases, thus allowing systematic interpretations of aglycone patterns. Possible pharmacological activities are briefly discussed.

Comparative analysis of leaf exudate flavonoids in Achillea subsect. Filipendulinae

Abstract Several populations each of 21 species united in subsect. Filipendulinae of Achillea sect. Millefolium have been studied for their leaf exudate flavonoids. Most species accumulated mainly methyl ethers of the flavonols 6-hydroxykaempferol and quercetagetin, predominantly as 4′-methylated derivatives. However, A. biebersteinii and allied species exhibited a strong tendency towards the formation of 3′-substituted analogues which are of very restricted occurrence within Achillea . The morphologically distinct species around A. ochroleuca are characterized by the additional formation of 6-hydroxyflavone methyl ethers which were rarely encountered in significant amounts in all the other studied taxa of this subsection. In some taxa, infraspecific variability was quite high, reflecting morphological and cytological plasticity. Relationships among these species as well as systematic and ecological aspects are briefly discussed.

Chemodiversity of Surface Flavonoids in Solanaceae

Abstract Several species of Nicotiana and Solanum and further members of the Solanaceae have been examined for their exudate flavonoids. Most of the aglycones are widespread flavonols, but rare and unusual flavonols were also found, e.g. in exudates of Physalis and Solanum species. Flavones occur throughout the family, but flavanones are rare. Our data are presented in comparison to previous results. The chemodiversity of the observed structures is discussed in relation to literature reports. Morphological and systematic aspects are briefly addressed.

C-Glycosylflavones as an Accumulation Tendency: A Critical Review

C-Glycosylflavones represent a special group of flavonoid glycosides both with respect to their chemical structure and presumed different biogenetic origin. Their accumulation and distribution in various plant groups has frequently been interpreted systematically; however, the application of chemotaxonomic congruence sometimes has led to incoherent results. This indicates the necessity for studying C-glycosylflavones primarily as an accumulation tendency before using them as systematic markers. Taking this into account, the distribution of C-glycosylflavones within the Compositae has been compiled and, on the basis of available data, their integration into the complete flavonoid complement analyzed. These results have been compared to those from other selected angiosperm groups, with special regard to the occurrence of certain combinations of different flavonoid glycosides with C-glycosylflavones. Despite the lack of detailed systematic surveys, the biosynthetic capacity of C-glycosylflavone accumulation in the Compositae was found to be relatively high. Mono-and di-C-glycosylflavones, including some with complex structures, are accumulated in the tribes Anthemideae, Heliantheae, Cynareae and Lactuceae. The genera of the Anthemideae and Heliantheae exhibited a very similar C-glycosylflavone profile, thus suggesting possible affinities. The tribes Eupatorieae, Astereae, Inuleae, Vernonieae and Senecioneae apparently accumulated only a small number of less complex C-glycosylflavones. Strikingly, di-C-glycosylflavones were often combined with a series of flavonoid O-glycosides, whereas predominantly C-glycosylflavone profiles showed a low percentage of co-occurring flavonoid O-glycosides. These combination trends could possibly serve as additional chemical characters. Various combination trends have been found within the angiosperms surveyed here. Mostly C-glycosylflavones co-occurred with flavonol 3-O-glycosides and (or) flavone 7-O-glycosides. Mutual exclusivity appeared to be very rare. A predominantly C-glycosylflavone pattern frequently contained a few flavonoid O-glycosides only. By comparison, the Compositae seemed to accumulate di-C-glycosylflavones as a part of a flavonolor flavone-dominated pattern to a greater extent than the other taxa studied here. Taxa accumulating C-glycosylflavones as a main tendency exhibited different degrees of specialization with respect to the substitution patterns of individual compounds. These patterns are much more conclusive than the mere presence/absence criterion. The available data suggest a reconsideration of the present dogma on flavonoid evolution. There is little evidence that C-glycosylflavones truly represent an intermediate stage in the reduction trend from flavonols to flavones. More knowledge on the biosynthesis and function(s) of C-glycosylflavones would be helpful for their interpretation as systematic features.ZusammenfassungC-Glykosylflavone unterscheiden sich strukturchemisch, wahrscheinlich aber auch biogenetisch von den übrigen Flavonoidglykosiden. Daher wurde ihre Verbreitung und Akkumulation häufig systematisch interpretiert. Die Anwendung der “chemotaxonomischen Kongruenz” als Interpretationsmodell erscheint jedoch problematisch. Zum besseren Verständnis des Merkmals C-Glykosylflavon-Akkumulation wäre daher eine Analyse der Akkumulationstendenz per se notwendig. Dies berücksichtigend, wurde die Verbreitung von C-Glykosylflavonen bei den Compositae analysiert, wobei besonders auch ihre Integration im gesamten Flavonoidprofil diskutiert wird. Die Ergebnisse wurden mit ähnlichen Analysen bei verschiedenen Angiospermen-Gruppen verglichen und die Kombination mit verschiedenen Flavonoid-O-Glykosiden eingehender studiert. Trotz der geringen Zahl vergleichender Untersuchungen bei den Compositae erscheint ihre Biosynthesekapazität relativ hoch: in den Triben Anthemideae, Heliantheae, Cynareae und Lactuceae kommt es zur Akkumulation von auch komplexeren mono-und di-C-Glykosylflavonen. Dabei zeigen vor allem Gattungen der Anthemideae und Heliantheae weitgehend übereinstimmende C-Glykosylflavon-Profile. Dagegen werden in den Triben Eupatorieae, Astereae, Senecioneae, Vernonieae und Inuleae nur die biogenetisch einfacheren Derivate in geringerem Ausmass akkumuliert. Auffallenderweise kommen di-C-Glykosylflavone häufig in Kombination mit dominierenden Flavonoid-O-Glykosiden vor, während in Profilen mit dominierender C-Glykosylflavon-Ausstattung die entsprechenden Flavonoid-O-Glykoside mengenmässig stark zurücktreten. Diese Kombinationstendenzen könnten sich als zusätzliches chemisches Merkmal erweisen. Unterschiedliche Kombinationstendenzen wurden bei anderen Angiospermen-Gruppen beobachtet. Meistens wurden C-Glykosylflavone mit Flavonol-3-O-Glykosiden und (oder) Flavon-7-O-Glykosiden co-akkumuliert. Dabei kommt es selten zum wechselseitgen Ausschluss von C-Glykosylflavonen und Flavonoid-O-Glykosiden. Meist enthält ein dominierendes C-Glykosylflavon-Muster wenige Flavonoid-O-Glykoside. Im Vergleich dazu scheint die Kombination von di-C-Glykosylflavonen und dominierenden Flavonoid-O-Glykosiden bei den Compositae häufiger zu sein als bei den übrigen hier untersuchten Angiospermen. Taxa mit dominierenden C-Glykosylflavon-Profilen zeigen vielfach ein unterschiedliches Ausmass an Spezialisierung im Substitutionsmuster der einzelnen Derivate. Diese Muster erscheinen als chemische Merkmale bedeutsamer als das Merkmal “Vorkommen versus Fehlen.” Aufgrund der bisherigen Daten erscheint daher eine Revision des bestehenden Dogmas der Flavonoid-Evolution erforderlich, da es wenig Hinweise auf die postulierte Rolle der C-Glykosylflavone als Zwischenstufe im Flavonol-Flavon Reduktionstrend gibt. Mehr Informationen über Biosynthese und Funktion von C-Glykosylflavonen könnten zu einem besseren Verständnis dieses chemischen Merkmals beitragen.

New exudate flavonoids of species from the Chrysanthemum complex (Asteraceae-Anthemideae)

Chrysanthemum segetum L., C. coronarium L. and Heteranthemis viscidehirta Schott are annual representatives of the subtribe Chrysantheminae Less. emend. Bremer (Anthemideae-Asteraceae). Contrary to earlier concepts, Chrysanthemum comprises only two species, occurring in the Mediterranean. The monotypic genus Heteranthemis, earlier considered to be Chrysanthemum, is distributed in the same area. This subtribe comprises further the Macaronesian endemic Argyranthemum Web. ex Schultz-Bip. (24 species) and the annual monotypic Ismelia Cass. (= C. carinatum; Bremer and Humphries, 1993). Phylogenetic studies confirmed the monophyly of this group (Francisco-Ortega et al., 1997; Oberprieler and Vogt, 2000). Chrysanthemum segetum L., C. coronarium L. and Heteranthemis viscidehirta were cultivated in the Botanischer Garten der Technischen Universitat Darmstadt. Voucher specimens are deposited in the herbarium of the Institut fur Botanik in

Distribution of externally accumulated flavonoid aglycones within the Achillea nobilis group

Forty-one collections of six species forming the Achillea nobilis group were analysed for their external aglycone patterns. Most species are characterized by the predominance of 6-methoxyflavonols, whereas the corresponding flavones are of limited distribution. The study was carried out to check primarily the infraspecific variability of these profiles. In addition, their use as possible taxonomic markers is also discussed.

C-Glycosylflavones in roots and aerial parts of some Achillea species

Four Achillea species collected from Turkey and Egypt have been shown to contain a mixture of C-glycosylflavones in their aerial parts. In addition A. fragrantissima and A. lycaonica had such compounds in their roots: these were absent from A. spinulifolia and A. aleppica.

Flavonoid glycoside accumulation trends of Achillea nobilis L. and related species

More than 50 collections of five species forming the Achillea nobilis group were analysed for their leaf flavonoid complement. Major accumulation trends were found to be C-glycosylflavones and flavonol 3-O-glycosides. The most common pattern consisted of the C-8-glycosylfiavones (vitexin and orientin), the C-6-glycosylflavone (isoorientin) together with minor amounts of di-C-glycosylapigenins and quercetin 3-O-glycosides. Additionally, C-6-glycosylflavones (isovitexin) and their 7-methyl ethers swertisin and swertiajaponin were sporadically accumulated, characterizing particularly two subspecies of A. nobilis. Whereas C-glycosylflavone dominated profiles were typical of most species, two taxa exhibited a flavonol dominated profile (A. ligustica; A. virescens p.p.). Regarding the infraspecific and interpopulational variations of flavonoid accumulation trends, their systematic and ecological significance is briefly discussed.