Eckhard Wollenweber

Technische Universität Darmstadt | TU · Research Area of Plant Sciences

Cuticular waxes of Viscum album subspecies and of V. cruciatum have been examined for their micromorphology and chemical composition. Wax crystalloids occur preferably as irregular platelets and rodlets, while deviant structures are found in small areas. Among the triterpenoids forming the wax layer, oleanolic acid is prevailing with some 80%. The...

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 mad...

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.

A new flavonoid, 2,3-trans-5,2'-dihydroxy-7,8-dimethoxy-dihydroflavonol-3-O-acetate, was isolated from the farinose coating on the lower leave surface of the fern, Notholaena sulphurea. The 2,3-cis diastereoisomer was isolated as a co-constituent. This novel acylated flavonoid is characteristic for the chemotype of N. sulphurea exhibiting yellow fr...

Cuticular waxes of Viscum album ssp. album contain oleanolic acid as main constituent, accompanied by aliphatic compounds like alkanes, esters and primary alcohols. A number of flavonol aglycones (methyl ethers of quercetin and kaempferol) have also been identified. Seasonal changes in amount and composition of cuticular waxes and the presence of f...

The exudate of Ozothamnus hookeri has been investigated for its non-flavonoid constituents. A new natural C6-C3 ester of a long chain fatty acid and seven structurally related kaurane-diterpenoids were isolated. Three of the latter are new natural products, too. A rare 8-methoxy flavonol was also identified.

A new oxyprenyl coumarin was isolated from the lipophilic exudate of Ozothamnus lycopodioides. Its structure was established as 7-(3,3'-dimethylallyloxy)-5-hydroxy-6-methoxycoumarin from its UV, MS and NMR spectral data, especially two dimensional experiments. In addition to six earlier reported flavonols, we found four highly substituted flavones,...

Twenty-two species of Scophulariaceae have been found to accumulate flavonoid aglycones externally on their leaves and stems. They belong to the genera Anarrhinum, Antirrhinum, Asarina, Calceolaria, Mimulus, and Odontites. Most of the flavonoids are methylated flavones and flavonols, some with 6-O and/or 8-O-substitution. One of them is the natural...

The prenyl ester and the phenylethyl ester of caffeic acid, formed in the bud excretion of poplar species, were shown recently to be the major contact allergens in bee-glue. An unambiguous synthesis of these compounds, based on the reaction of caffeic acid with 1-bromo-3-methyl-2-butene and with beta-bromoethylbenzene, respectively, is reported. Th...

Roridula dentata and R. gorgonias, two South African plants that were formerly believed to be carnivorous, exhibit an extremely sticky exudate at the tips of secretory trichomes. Unlike the trapping mucilage of Droseraceae, it does not consist of acidic polysaccharides. The Roridula trapping glue was found to be a mutual solution of mainly dihydrox...

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-subs...

The bud exudates of Populus nigra, P.trichocarpa, and P.grandidentata x tremuloides were analyzed for the presence of phenolics and flavonoids. A novel natural product, caffeic acid γγdimethylallyl ester, was identified from P.nigra, along with further phenolics such as P-hydroxyacetophenone, dimethyl caffeic acid, cinnamoyl cinnamata and vanillin....

Leaf and stem exudate of Ozothamnus scutellifolius, previously reported to contain 21 flavonoid aglycones, was now investigated for its terpenoid composition. Seven structurally related diterpenoids were identified. One of them, 16a,19-diacetoxy-enf-kaurane, is a novel natural product.

The terpenoid excretion on buds of Alnus glutinosa is shown to contain free flavonoid aglycones. These are pectolinarigenine, centaureidin, the 3,6-dimethylether, 6,4′-dimethylether and 3,6,4′-trimethylether of 6-hydroxykaempferol and isorhamnetin.

Bud excretions of Prunus and Rhamnus species are shown to contain free flavonoid aglycones. While in Rhamnus these are the common flavonols known long ago as glycosides in berries and leaves, there are some rare aglycones to be found in Prunus avium, namely dihydrowogonin, jaceidin, 6-methoxykaempferol and its 3-methyl ether.

Pityrogramma triangularis var. viscosa is one of the clear­ly defined varieties within the Pityrogramma triangularis complex. The flavonoid constituents of its frond exudate show a pattern characteristic for this taxon. The major component of the exudate could now be isolated. By spectroscopic methods it has been shown to be 2′,6′,4-trihydroxy,4′-m...

Leaves and young twigs of Hypericum balearicum L. exhibit lipophilic glandular products that can be re­ covered by rinsing green aerial parts with acetone. Major components of the resinous material are the triterpenes lupeone and lupeol. The intensely yellow col­ our of the acetone solution is due to a novel natural product, identified as 1,2,5-tri...

Mannose exudates on fronds of Notholaena species are known to consist of navonoid aglycones. These are predominantly methylated flavones and flavonols, sometimes chalcones and dihydrochal-cones. Flavonols with unusual properties, excreted as major farina components by some species, have been found to be derivatives of methylated flavonols, esterifi...

The hawkweed Hieracium intybaceum is covered with glandular trichomes that produce a sticky resinous exudate. This material, assumedly of terpenoid nature, contains trace amounts of flavonoid aglycones. They could be identified to be known flavones and flavanones. This is the first time that an alpine Asteraceae was found to exude flavonoid aglycon...

The lipophilic epicuticular material of four shrubby Rosaceae from the Southwestern USA has been studied. They all exhibit triterpene acids as major products. Adenostoma sparsifolium and Cowania mexicana var, glaber, the two species in which glandular structures and a lipophilic excretion are obvious, produce free flavonoid aglycones as well. In Ad...

A fraction of poplar bud exudate was analyzed by GC/MS and the novel aliphatic hydrocarbon esters 2-methylpropyl-, 2-methyl-2-propenyl-, 2-methylbutyl-, 3-methylbutyl-, 2-methyl-2- butenyl-, 4-methylpentyl-, (5)-methylhexyl- and 3,7-dimethyl-2,6-octadienyl(geranyl)- caffeate were identified.

The flavonoid aglycones excreted by and deposited on aerial parts of 12 species of tribe Eupatorieae, including 10 species of Eupatorium (narrowly defined), Conoclinium coelestinum, and Brickellia eupatorioides, have been analyzed. The flavonoid pattern of Eupatorium is dominated by 6-O-methylated flavones, and there are relatively few differences...

Members of the genus Cistus excrete a leaf resin that consists mainly of terpenoids. This resin also contains methylated flavonoids as aglycones. Rare methyl derivatives of myricetin have been isolated from C. monspeliensis, along with uncommon methyl derivatives of quercetin. Further flavonoids encountered in the leaf resin of this and six further...

Prolonged UV irradiation of ceroptene yielded substantial quantities of a compound identical with thepreviously described isoceroptene, a trace constituent isolated from the farinose exudate of Pityrogramma triangularis. The improved MS, 'H NM R and 13C NMR analyses, together with X-ray diffraction, made possible by theavailability of synthetic iso...

The farinose frond exudate of the fern Notholaena aschenborniana was previously shown to contain a mono­ acetate and a mono-butyrate of a 8-hydroxyflavonol as major constituents and the same pair of esters of a second 8-hydroxyflavonol as minor components. Now we have been able to identify the 8-acetates of two further flavonols. The structures of...

2′,5′-Dihydroxyflavone and its 5′-acetate were isolated from the farinose exudate of Primula japonica and P. pulverulenta. Their structures were elucidated by spectroscopic methods and confirmed by synthesis. Both flavones are novel natural products.

Notholaena fendleri is a rare representative of the genus, growing mainly in Colorado/USA. The white farinose exudate on the lower surface of its pinnules is composed partly of waxy material and partly of ñavonoid aglycones. The flavonoid moiety consists mainly of methyl derivatives of the flavanones naringenin and eriodictyol. The eriodictyol meth...

In young plants of Eucalyptus globulus the leaves are covered with a whitish epicuticular layer. This leaf wax contains small amounts of C-methylated flavones as aglycones. A novel flavone has now been identified as 5, 4′-dihydroxy, 7-methoxy, 6-methyl-flavone (8-desmethyl-sideroxylin). Another minor external flavone is chrysin. On leaves of E. sie...

In Central Europe and other temperate regions the lipophilic bee hive product propolis normally originates from the bud exudate of poplar trees that is collected by the bees. Based on bee observations, various other sources have been discussed in particular for tropical regions, but in only few cases the origin has been proved by analytical methods...

Representatives of the genera Odixia and Ozothamnus, Australian Asteraceae belonging to the tribe Gnaphalieae, have been analyzed for the presence of flavonoid aglycones accumulated on leaf and stem surfaces. Fifty-two more or less lipophilic flavonoids have been identified. Methyl ethers of apigenin, luteolin, kaempferol and quercetin are abundant...

Biflavonoids are well known to occur in many Gymnospermae. Here we report on their occurrence in epicuticular material of a number of species. Several compounds are characterized by detailed NMR studies and FAB-MS. They are identified as amentoflavone, bilobetin, podocarpus-flavone A, sciadopitysin, dihydrosciadopitysin and cupressuflavone.

A series of Asteraceae, belonging to the tribes Astereae, Eupatorieae, Helenieae and Heliantheae, have been analyzed for the presence of flavonoid aglycones accumulated on leaf and stem surfaces. Methyl ethers of apigenin, luteolin, kaempferol, and quercetin as well as methyl ethers of their relevant 6-hydroxy derivatives were abundant, whereas 8-O...

Yellow coloration of pollen in some exceptional cases can be caused by the presence of intensely coloured flavonoids. Derivatives of herbacetin (sexangularetin) and of gossypetin (limocitrin) have been found as “yellow flavonols” in the pollen of some species of Paeonia and of Rumex. The pollen of Spinacea oleracea contains the 6-methyl ether of ga...

The major constituent of the yellow frond exudate of the fern Notholaena sulphured was identified by spectroscopic methods as 3,5,2′-trihydroxy-7-methoxy-8-acetoxy flavone and its structure was confirmed by synthesis. This novel natural flavonoid was also detected in the frond exudate of five other Notholaena species. In the yellow form of N. sulph...

Flavonoid aglycones were detected as minor constituents of the leaf wax of the Myrtaceae Leptospermum laevigatum. They belong to the rarely encountered C-methyl flavonoids. One of them is a new natural product, 5-hydroxy-3,7,3′.4′-tetramethoxy-6-C-methyl flavone.

From the farinose frond exudate of the fern Notholaena rigida two new triterpenes have been identified. They were found to be the C-24 epimers of 12β-acetoxy-24,25-diO-isopropylidene-dammarane-3β, 20(S),24,25-tetra-ol. A survey of all triterpenes found in Notholaena is presented.

From the farinose frond exudate of the fern Notholaerna rigida two new triterpenes have been identified. They were found to be the C-24 epimers of 3β-acetoxy-24, 25-diO-isopropylidene-12ß, 20(S),24,25-tetrahy-droxy-dammarane, A third triterpene is identical with the known compound pyxinol, (20S,24R)-20,24-epoxy-dammarane-3ß,12ß,25-triol.

A series of new flavonoid aglycones have been identified in the frond exudates of the fern Cheilanthes argentea, in five species of Notholaena, in Pityrogramma triangularis, and in Platyzoma microphylla. These aglycones comprise several rare flavonoids and five novel natural products: 5,7,8-trihydroxy-3-methoxy-6-methyl flavone, 3,5,2′-trihydroxy-7...

A novel flavonoid, the natural 3-acetyl-derivative of pinobanksin, has been isolated from the lipophilic bud excretion of poplar. The structure and spectral analysis (UV, IR, NMR, M S). The strated

Several species of the large genus Artemisia have been analysed for the flavonoid aglycone composition of their leaf exudates. These species belong to different taxonomic groups within Artemisia. Flavone and flavonol aglycones were found as the major flavonoid constituents of the leaf exudates. Many of these compounds were 6-methoxylated, with addi...

Extraction of pollen of Nothofagus antarctica with acid hydrolysis yields kaempferol, quercetin, the rare flavonol sexangularetin, and naringenin. The tetrahydroxy-chalcone isosalipurpol is shown for the first time to occur in such high amount as free aglycone in mature pollen; it yields naringenin in usual extraction procedures. The bright yellow...

Myricetin-3,7,3',4'-tetramethyl ether has been isolated as an aglycone from the acetone wash of Tillandsia usneoides. It is thus shown to be deposited externally, onleaf and stem surfaces. We suggest that the previously reported lipophilic flavonoids from this and other species are also exudate constituents.

Four flavonoids have been identified from the leaf and stem resin produced by Baccharis bigelovii (Asteraceae) in addition to twelve previously described aglycones. A flavonol (alnusin) and a dihydroflavonol (alnustinol) with 3,5,7-trihydroxy substitution had both been reported only twice before. The novel compound 2ß,5,7-trihydroxyflavanone is rem...

The major components of the white exudate or farina from the abaxial side of fronds of the fern Cheilanthes argentea are the diterpenoid acids ent-8(17), E-13-labdadien- 15-oic acid and its 3 R-hydroxy derivative. This is the first report of the first of these compounds as a natural product. Both are highly crystalline. Plants from the Asian mainla...

Several lipophilic phenolics were found in leaf resins of Baccharis species, reported earlier to produce terpenoids and flavonoid aglycones. They were identified by NMR and GC/MS studies, respectively. The structure of 2',4'β-trihydroxy-6'-methoxychalcone from B. salicifolia was confirmed by synthesis. Phenylethyl caffeate and benzyl caffeate were...

δ-Amyrenon, known previously as constituent of leaves in the genus Alnus, is shown to form an important part of the triterpenoid excretions on buds of various alder-trees.

Gold-back ferns and silver-back ferns of the genus Pityrogramma are known to produce chalcones and dihydrochalcones, deposited as a farina on the under surface of their fronds. In Cheilanthes and Notholaen a mostly methy­lated flavones and flavonols are excreted, but some species are shown here to accumulate chalcones and dihydrochalcones, too. The...

Leaves of a number of Ericaceous plants have a thin epicuticular layer that consists mostly of triterpenes. InKalmia angustifolia, K. latifolia and K polifolia as well as in Gaultheria procumbens and G. shallon this material alsocontains trace amounts of flavonoid aglycones. In Kalmia they are the 3-OMe-derivatives of four C-methyl flavones reporte...

A series of methylated flavonols and two methyl flavones have been identified in the exudate of the American gumweed species Grindelia glutinosa and Grindelia robusta. They resemble the flavonoid patterns observed in other species of this genus, which thus shows a tendency for accumulation of methylated flavonols.

The resinous material excreted by aerial parts of snakeweed, Gutierrezia sarothrae, was analyzed for flavonoid aglycones. Six m ajor flavonoids were characterized by their spectral data; nine minor flavonoids were identified by direct comparisons with markers. The major flavones form three pairs of isomeric products, five of which are 6,8-methoxyla...

A flavanone with 3'-OH as the sole B-ring substituent has been reported recently as a leaf and stem exudate constituent of Encelia stenophylla. The correctness of this unusual substitution is confirmed by synthesis of this flavanone.

The viscid exudate found on fronds of the fern, Cheilanthes kaulfussii, consists of terpenoids in which flavonoid aglycones are dissolved. One of the terpenes is shown to be ent-kaur-16-en-19-oic acid. The farinose frond exudate of Notholaena pallens contains this acid as the major constituent and its 3 R-hydroxy derivative, together with flavonoid...

The monotypic genus Leucocyclus, consisting of only two subspecies, was investigated for its exudate flavonoids. Major flavonoid aglycones were polymethoxyderivatives of 6-hydroxyflavones and, to a lesser extent, of 6-hydroxy-flavonols. The two subspecies differed in their accumulation trends, but populational variation reduced the significance of...

The chemical composition of the leaf resin of Pluchea odorata has been studied from material collected in Tamaulipas, Mexico. It mostly consists of triterpenes and phytosterols and an eudesmane type sesquiterpene. Very small amounts of ten different flavonol aglycones occur, dissolved in this resin; most of them are 6-methoxy compounds. A compariso...

Bud Exudates of three Betulaceae were analyzed for minor flavonoid aglycones. Three flavonoids not previously reported were found in Alnus koehnei, four in Betula nigra. A novel flavonol, morin-3, 2',4’-trimethyl ether, is described for Ostrya carpinifolia. © 1991, Verlag der Zeitschrift für Naturforschung. All rights reserved.

Complex flavonoids that are typical for the frond exudate in ferns of the genus Pityrogramma are surveyed to demonstrate their close structural relation. Two such compounds. isolated earlier from the exudate of Pityrogramma calomelanos var. aureoflava are prepared by an unambiguous synthesis. Direct comparisons of the synthetic products, namely p-(...

Anaphalis margaritacea, Gnaphalium chilense and G.microecephalum have been analyzed for flavonoid aglycones deposited externally on aerial parts. Anaphalis was found to produce, among others, several rare flavonoids, all of which are O-substituted in position 6 and mostly also in position 8. Both Gnaphalium species exhibit 3,5-dihydroxy-6,7,8-trim...

In addition to several previously reported flavonoid aglycones, the white farinose material accumulating on the lower leaf surface of Notholaena grayi contains as major constituent a triterpene. This product has now been identified by detailed NM R spectroscopic studies as the novel (24R)-3α, 24, 25-trihydroxylanost-9(11)- en-28-oic acid.

Eriodictyon sessilifolium, an endemic Hydrophyllaceae of Baja California (Mexico), has been studied for the natural products exuded by glandular trichomes covering its leaves and stems. Major components of this exudate were isolated and identified by spectroscopic methods to be 4-hydroxy-3-(2, 3-dihydroxy-3-methylbutyl)-benzoic acid methyl ester (1...

The glaucous epicuticular layer on the undersurface of the leaves of Polypodium glaucinum and the white exudatematerial on the lower surface of the sterile pinnae of Plagiogyra formosana is shown, mainly by spectroscopical methods, to consist of a mixture of 9(ll)-femene and 21-epi-9(ll)-femene, in both instances in a ratio of ca. 4:1. The 13C-NMR...

Seven species of Salvia and one species of Trichostema were analyzed for their exudate flavonoids. They were found to exhibit flavonoid aglycones in various numbers and different patterns. Most of these are flavones, in which 6-methoxy-substituted compounds predominate.

From the farinose frond exudate of the fern Notholaena rigida two new triterpenes have been identified. They were found to be the C-24 epimers of 24,25-diO-isopropylidene-3β, 20(S)-trihydroxy-dammarane.

The leaf exudate of Ozothamnus ledifolius, previously reported to contain a series of flavonoid aglycones, mostly consists of a mixture of terpenoids. From this resinous material we now identified four sesquiterpenes, a diterpenediol and two pentacyclic triterpene acids. In the phenolic portion we found three phenylethyl esters.

The flavonoid aglycones excreted by aerial parts of three Viguiera species have been analyzed. One of them is a rare natural product. So far unpublished NMR data are reported for three flavones. Each species of V. sec­tion Hypargyrea exhibits a distinctive flavonoid profile based on different patterns of methoxylation, but the taxonomic section as...

Nineteen flavonoid aglycones have been identified from the external stem and leaf resin of Ericameria laricifolia by thin layer co-chromatography with authentic samples. Kaempferol, quercetin, apigenin, and their methyl ethers have been found, along with luteolin and 6-methoxy luteolin. It is suggested that future flavonoid chemosys-tematic studied...

Ten methylated flavonols have been identified in the lipophilic resinous exudate found on aerial parts of Grindelia tarapacana, a gum weed species of Chile.

Several triterpenes were isolated from the lipophilic frond exudates of three Notholaena species.In the terpenoid portion of N. Candida we identified two novel cycloartane type triterpenes.N. rigida yielded protolyofoligenic acid, a cycloartane type product that has been reported once before from a higher plant. From N. schaffneri, a novel dammaran...

The sticky lipophilic exudates produced by glands on inflorescences of Rosa centifolia cv. muscosa and Rubus phoenicolasius contain flavonoid aglycones. Ten different flavonoids were identified from Rosa centifolia cv. muscosa, including several flavones with 6,8 -methoxy substitution. In Rubus phoenicolasius, the major flavonoids are methyl ethers...

Fronds of the neotropical fern Pityrogramma trifoliata produce a farinose exudate which consists mainly of a dihydrochalcone. The structure of some minor constituents has been elucidated by spectroscopic methods. They are shown to be representatives of a novel class of complex flavonoids, composed of a flavonoid and a neoflavonoid moiety. In other...

Two new triterpenoids, isolated from the frond exudate of the fern Notholaena rigida, have been identified as 3 ß, 12 ß,25-trihydroxy-(20 R-24 R)-epoxy-dammarane- 12-acetate (1), and 24 R,25-diO-isopropyliden-9(19)-cyclolanostan-3 ß-ol (5), based on NMR spectroscopic studies.

Hymenoclea salsola (Asteraceae), a dominant shrub of the desert areas of California and Baja California, Mexico, secretes high amounts of resin on the leaf surface. Chemical analysis of the resin revealed the presence of a complex mixture of flavonoid aglycones. Among the compounds identified is the rare 2′, 4′, 6′- OH Chalcone, previously not know...

Leaves and other aerial parts of several succulent species each of Kalanchoe and Senecio exhibit more or less obvious wax coatings. The major components of these waxes were identified to be pentacyclic triterpenes. Some of these are rare natural products, while others are rather widespread. © 1995, Verlag der Zeitschrift für Naturforschung. All rig...

Calathea lutea lives in rain forests of Central America. It produces a conspicuous wax coating on the under surface of the leaves. As contribution to the as yet rather poor chemical knowledge on the Marantaceae, the composition of this wax has been analyzed. By GLC and MS it could be shown to consist mainly of odd numbered re-alkanes and even numbe...

Seven species of the genus Baccharis have been analyzed for flavonoid aglycones. Many known methylated flavones, flavonols and flavanones were identified. From B. sarothroides, two novel flavonols were isolated and elucidated as 5,7,4′-trihydroxy-3,6,8-trimethoxyflavone and its methyl ether, 5,4′-dihydroxy-3,6,7,8-tetramethoxyflavone. Previous lite...

Leaves and stems of Fouquieria splendens were found to accumulate flavonoid aglycones on their surfaces. Three flavones and five flavonols have been identified.

2′,6′,4-OH, 4′-OMe-chalcone (neosakuranetin) and 2′,6′,4-OH, 4′-OMe-dihydrochalcone (asebogenin) were found as major constituents of the frond exudate on one in­ dividual plant of Pityrogramma calomelanos. Galangin-5,7-dimethyl ether was isolated from the farina on fronds of a certain population of Pityrogramma triangularis as a novel natural flavo...

Isoceroptene, a polyphenol isolated in trace amount from the farinose frond exudate of Pityro­gramma triangularis, is shown by spectroscopic means to possess the structure of one of the two possible “flavanone” isomers formed by ring closure of the “chalcone” ceroptene. The tautomeric structures best representing ceroptene and a related dihydrochal...

The frond exudates of the two gymnogrammoid ferns, Notholaena peninsular is and N. pallens, consist mainly of a diterpene, accompanied by small amounts of flavonoid aglycones. The diterpenes from both sources are shown to be identical. Their structure has been established by spectroscopic methods as (-)-kaur-16-ene-19-oic acid. This result is confi...

Leaf-extract of Rhus salicifolia is shown to contain, besides myricetin, quercetin and kaempferol, the rare myricetinmethylethers syringetin and europetin and the quercetin-methylethers ombuin and rhamnetin. The structures are proved by spectral analysis (UV, MS, NMR) and by cochromato­ graphy with authentic substances

The white farinose exudate on the fronds of Cheilanthes argentea contains a series of flavanones as minor constituents. These were identified by spectroscopic methods as: 5,4′-diOH,6,7-diOMe flavanone and its 4′-OMe derivative, 5,4′-diOH,7,8-diOMe flavanone and its 4′-OMe derivative, 5,6-diOH,7,8,4′-triOMe flavanone, 5,4′-diOH, 6,7,8-triOMe flavano...

The antioxidant activity of eight Egyptian propolis samples from different localities was evaluated by the antioxidative potential and capacity of the DPPH-ESR signal, superoxide anion generated in the xanthine-xanthine oxidase (XOD) system and low density lipoprotein (LDL) peroxidation assay. As, F, Is and D samples showed the highest antioxidativ...

Members of several genera of Asteraceae, belonging to the tribes Mutisieae, Cardueae, Lactuceae (all subfamily Cichorioideae), and of Astereae, Senecioneae, Helenieae and Heliantheae (all subfamily Asteroideae) have been analyzed for chemodiversity of their exudate flavonoid profiles. The majority of structures found were flavones and flavonols, so...

Three members of the tribe Gnaphalieae and six members of the tribe Inuleae (Asteraceae) were analyzed for their exudate flavonoids. Whereas some species exhibit rather trivial flavonoids, others produce rare compounds. Spectral data of rare flavonoids are reported and their structural identification is discussed. 6-Oxygenation of flavonols is a co...

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...

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 qu...

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 p...

The structures 4′,5-dihydroxy-2′,3,7,8-tetramethoxyflavone and 5-hydroxy-2′,3,4′,7,8-penta-methoxyflavone have been attributed to two new compounds isolated from a farinose exudate of Notholaenaaffinis; this result is derived from uv, ms, and nmr spectra of the natural products and their derivatives.

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.

More than 60 accessions of various Dionysia spp. were analysed for their exudate flavonoid composition. Many Dionysia spp. accumulate the typical Primula flavonoids with irregular substitution (unsubstituted flavone, its 2',5'-substituted derivatives and corresponding 5-OH-flavones), but flavones, flavonols and flavanones with regular 5,7-diOH-subs...

The flavonoid pattern of an acetonic extract of Grindelia robusta Nutt. was investigated in detail. The flavonoids were enriched by CC. In addition to twelve known methylated exudate flavonols four compounds were identified for the first time in G. robusta. Several substances of the flavonoid complex, among them the main compounds quercetin-3-methy...

Several new accessions of the genus Primula and of the closely related Cortusa matthioli have been studied for their exudate flavonoid profiles. Unsubstituted flavone, 5-hydroxy-, 2'-hydroxyflavone and 5,2'-dihydroxyflavone were found as main components. Several other rather unusual substitution patterns were also found. 8-O-Substituted flavones ap...

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 diff...

Tricin (3′,5′-dimethoxy-5,7,4′-trihydroxyflavone) is a characteristic flavone constituent of cereal grain plants that is credited for a variety of potential health benefits to humans. We have characterized the flavone-specific O.-methyltransferase genes of barley (Hordem vulgare. L., Gramineae), HvOMT1,. and maize (Zea mays. L., Gramineae), ZmOMT1....

This paper presents a review of the occurrence of tricetin and its methyl ethers, with respect to their occurrence in the free state. In addition to literature data, our tabulated survey also includes a dozen unpublished results. The review indicates that 5,7,3′,4′,5′-pentahydroxyflavone and its methyl derivatives are more widespread than was known...