Flavonoid aglycones from the leaf and stem exudates of some Geraniaceae species.

Six species of Pelargonium and one species of Geranium were studied for their surface flavonoids. Some of them were found to exhibit an unexpectedly high number of methylated flavonoids, mostly flavonols. The chemotaxonomic significance of exudate flavonoid diversification is shortly addressed.

Exudate flavonoids of some Juglandaceae.

Six species of Juglandaceae have been checked for the occurrence of flavonoid aglycones on their leaf and fruit surfaces. Except for one, they exhibit flavonols, mostly methyl ethers of kaempferol and quercetin, including 6-O-substituted derivatives. Apigenin and acacetin are the only flavones found so far. Flavonoids accumulated on leaves are different from those excreted on green fruits. It has become evident that in future studies greater attention must be paid to the localization of flavonoid aglycones in different plant organs.

Chemodiversity of exudate flavonoids in Cassinia and Ozothamnus (Asteraceae, Gnaphalieae).

The lipophilic exudates deposited on aerial parts of four species of Cassinia and twelve species of Ozothamnus (Asteraceae, Gnaphalieae) have been analyzed for the presence of flavonoid aglycones and some other phenolics. A total of 55 flavonoids were identified, including several rare flavonols. Flavonols are prevailing over flavones, and 8-O-substitution is dominant in both groups. Ozothamnus rosmarinifolius is exceptional in producing several coumarins. Four dihydrobenzofurans have also been identified from this species. Cluster analysis and principal coordinate analysis of the flavonoid data provide support for combining species of Cassinia and Ozothamnus into a single genus.

Chemodiversity of surface flavonoids in Solanaceae.

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.

Exudate flavonoids of eight species of Ceanothus (Rhamnaceae).

Leaf glands of Ceanothus species excrete a lipophilic material that contains a variety of flavonoids. Most of these are aglycones, but some glycosides were also observed. Seven out of eight species exhibit flavonols, whereas flavones are excreted by only one species. Four species produce flavanones and dihydroflavonols; one excretes a remarkable quantity of flavonol glycosides. The exudate flavonoids thus form different patterns that might be characteristic for different Ceanothus species.

Flavonoids and terpenoids from the resinous exudates of Madia species (Asteraceae, Helenieae).

The resinous material accumulated on aerial parts of Madia species is shown to consist mainly of diterpenes, containing a series of flavonoid aglycones. A6- and/or 8-O-substitution is characteristic for many of these flavonoids. Three known rare diterpenes were found and the structure elucidation of a diterpene with a new carbon skeleton, named madiaol, is reported.

Taxonomic significance of flavonoid variation in temperate species of Nothofagus.

Forty-two flavonoids and a stilbene (pinosylvin) were identified in the leaf exudates of 11 temperate species of Nothofagus from South America, Australia and New Zealand. The flavonoid profiles demonstrate significant taxonomic value at the subgeneric level. Most species of subgenus Fuscospora are characterized by the presence of pinosylvin, galangin and galangin methyl ethers. Kaempferol-type flavonols are abundant in subgenus Lophozonia while these flavonols are largely absent from species of subgenus Fuscospora. The flavonoid patterns are largely in agreement with a recent subgeneric classification of Nothofagus.

Externally accumulated flavonoids in three Mediterranean Ononis species.

The Mediterranean Ononis species, O. fruticosa, O. natrix subsp. ramosissima and O. tridentata, have been analyzed for their exudate flavonoids. More than 20 flavonoid aglycones were identified, some of which are rather rare natural compounds. One of them, namely hypolaetin-8,3',4'-trimethyl ether, had been found only once before. The results are presented in a table along with literature data, and the chemotaxonomic impact of the flavonoid patterns is discussed.

On the occurrence of exudate flavonoids in the borage family (Boraginaceae).

Externally accumulated flavonoid aglycones have been found for the first time in Nonea species. They exhibit only flavones, one of them being the rare tricetin-4'-methyl ether. Within the subfamily Boraginoideae, exudate flavonoids appear to be a rare character.