THE FLAVONOIDS OF LASTHENIA (COMPOSITAE)

Lasthenia (Compositae: Helenieae), a western North American-Chilean genus of 16 species, produces 22 flavonoid glycosides. Flavonoids are the chalcones butein and okanin, the aurones maritimetin and sulfuretin, the flavone luteolin, and the flavonols kaempferol, quercetin, and patuletin. The presence or absence of various of these classes of compounds in general follows sectional alignments in the genus, confirms affinities based on morphological and cytological evidence, and suggests relationships of problematical species. Intraspecific variation in flavonoid constituents occurs in several species, and in one taxon intrapopulation variation seems to exist as well. Evolution within Lasthenia has been associated with a loss of the ability to produce or accumulate luteolin, chalcones, and aurones; an increase in diversity of quercetin glycosides; acquisition of the ability to produce patuletin; and an elaboration of glycosylation patterns of patuletin.     

Foliar flavonoids of North American Solanum section Solanum

A total of ten flavonoids, all flavonols, were isolated from leaves of eleven species of Solanum sect. Solanum. Most species had relatively few compounds, primarily quercetin 3-O-glycosides. Little intraspecific variation in flavonoids was observed, except in S. americanum were it correlated with previously recognized races. Flavonoid data are of little help in determining ancestries of polyploid species, but do rule out S. sarrachoides as a progenitor of S. villosum and S. nigrum. Solanum sarrachoides is unique among species examined in having free flavonoid aglycones as well as extensive 3-O-methoxylation.     

Flavonoids from tribe Delphineae (Ranunculaceae): Phytochemical review and chemotaxonomic value

This review summarizes the flavonoids isolated from three genera, namely, Aconitum, Delphinium, and Consolida, belonging to tribe Delphineae in the Ranunculaceae family for the first time. A total of 104 distinct flavonoid components, including 85 flavonols, 13 anthocyanins, four flavones, and two neoflavones, have been isolated from 44 members of tribe Delphineae. Flavonols account for the largest proportion and can be regarded as the dominant group of flavonoids in this tribe. Of the 104 isolated flavonoids, 55 are novel, indicating the high chemical diversity among the flavonoid constituents of Delphineae plants. Flavonoids in Delphineae plants exhibit chemotaxonomic significance, characterizing certain Delphineae species well. Flavonol glycosides, as the major flavonoid constituents in the investigated Delphineae species, could also serve as valuable chemotaxonomic markers in addition to diterpenoid alkaloids for the identification of Delphineae species.     

Flavonoids of artificial interspecific hybrids in Lasthenia

The flavonoids of artificial interspecific hybrids in Lasthenia indicate differences in inheritance patterns among various classes of these compounds. Inheritance of production of anthochlors, kaempferol, and some patuletin glycosides is additive. Inheritance of production of luteolin and quercetin glycosides is not always additive, and in some progenies quercetin glycosides are produced that do not occur in the parents.     

Flavonoid patterns and systematics in Eleusine

A survey of leaf flavonoids was conducted on Eleusine coracana ssp. coracana and ssp. africana, E. indica, E. multiflora, E. tristachya, E. floccifolia, and E. compressa. Twenty phenolic compounds were detected. Those identified were: orientin, isoorientin, vitexin, isovitexin, saponarin, violanthin, lucenin-1, and tricin. The study revealed a general generic flavonoid pattern except for E. compressa, which occupies an isolated position in Eleusine. Flavonoids of the perennial E. floccifolia and the annuals E. multiflora and E. tristachya are markedly different from those of cultivated E. coracana, suggesting that these species are only distantly related to the crop. The morphologically well defined E. coracana—africana—indica group also forms a unit in respect of flavonoids. Subspecies africana exhibits a higher flavonoid similarity to ssp. coracana (finger millet) than does E. indica. The weedy race of ssp. africana usually combines flavonoids of both the wild and domesticated subspecies. The flavonoid pattern of the dedza race of ssp.africana is identical to that of finger millet, suggesting either a direct origin of the crop from this race, or extensive introgression from the crop into ssp. africana. A lack of qualitative differences in flavonoids between cultivated races of finger millet is indicative of the genetic stability of these compounds. The flavonoid data confirms the domestication of finger millet from ssp. africana.     

THE FLAVONOIDS OF ONAGRACEAE: TRIBE EPILOBIEAE

Data for the flavonoids of each of the species of Boisduvalia and each of the 14 species of Epilobium that constitute the 5 sections except for sect. Epilobium are presented. An analysis of nearly 100 populations showed that 7 flavonol 3-O-glycosides based on kaempferol, quercetin, or myricetin aglycones are present among the several species. All 7 compounds are present in each of the 2 genera but certain patterns of variation, especially in the loss of arabinosides, are noted among the several sections of the two genera. An intersectional comparison of the variation correlates flavonoid patterns more with the relative evolutionary advancement of specialization of the taxa than with their phyletic relationships. Further, a trend of decreased glycosylation with advancement within the tribe is documented. Both points are contrary to what is generally assumed for flavonoids in evolutionary studies.     

CHEMO-DEMES OF DIPLOID AND TETRAPLOID THELESPERMA SIMPLICIFOLIUM (HELIANTHEAE,COREOPSIDINEAE)

Selected secondary biochemical constituents (mainly flavanoids) contained in methanol leaf extracts of 11 taxa in the genus Thelesperma were analyzed via two-dimensional paper chromatography. With but one exception all produce an essentially identical array of these compounds. Since this common or “generic” biochemical profile is present regardless of the morphological, ecological, and cytological differences among and within the various species, it is impossible to make accurate specific identifications on the basis of chromatographic data alone. Recently, however, morphologically identical, but allopatric, diploid and tetraploid races of T. simplicifolium were discovered which differ radically in respect to these secondary biochemical components. Their infraspecific biochemical differences are so absolute that it is possible to predict accurately the ploidy level and geographic source of any given individual from its chromatographic profile. The evolutionary implications of these biochemical differences are also discussed briefly.     

Intra- and interspecific variations in vacuolar flavonoids among Ficus species from the Budongo Forest,Uganda

Leaves of 14 species of Ficus growing in the Budongo Forest, Uganda, were analysed for vacuolar flavonoids. Three to six accessions were studied for each species to see whether there was intraspecific chemical variation. Thirty-nine phenolic compounds were identified or characterised, including 14 flavonol O-glycosides, six flavone O-glycosides and 15 flavone C-glycosides. In some species the flavonoid glycosides were acylated. Ficus thonningii contained in addition four stilbenes including glycosides. Most of the species could be distinguished from each other on the basis of their flavonoid profiles, apart from Ficus sansibarica and Ficus saussureana, which showed a very strong intraspecific variation. However, on the whole flavonoid profiles were sufficiently distinct to help in future identifications.     

THE FLAVONOIDS OF THE DECIDUOUS RHODODENDRON OF NORTH AMERICA (ERICACEAE)

The native Azaleas of North America (Rhododendron: subgenus Pentanthera) produce 58 flavonoids in five aglycone classes: flavonols, dihydroflavonols, flavanones, dihydrochalcones and chalcones. A comparison of the flavonoids of selected samples of these species indicated that the compounds generally occur as species specific ensembles. Species were grouped into “alliances” based on common flavonoid constituents and a phylogenetic treatment of the group was developed. Evolutionary trends of flavonoids within subgenus Pentanthera are not well-defined but appear to be associated with a loss of the ability to synthesize some compounds and a decrease in diversity of glycosides and methoxylated flavonoids. Intraspecific variation in flavonoids was found in Rhododendron canescens, R. alabamense and R. austrinum when these were sampled on a population basis.     

Flavonoids as taxonomic markers in old world Lupinus species

In a leaf survey of 54 specimens of 11 Old World Lupinus species three classes of flavonoids were detected: flavones (in 82%), flavonols (in 36%) and flavone C-glycosides (in 55%). The rough-seeded species were clearly distinguished from the smooth-seeded taxa by the presence of a novel 2′-hydroxyflavone, luteolin and flavone C-glycosides as major leaf constituents and by the absence of flavonols. Within the smooth-seeded species, there are three flavonoid patterns: (a) flavonols only, L. albus; (b) flavones and flavonols, L. luteus, L. hispanicus and L. angustifolius; and (c) flavones only, L. micranthus. L. angustifolius further differed in uniquely producing diosmetin as a major leaf constituent. These divisions coincide exactly with previous groupings based on alkaloidal and morphological data. Amongst the 12 samples of L. angustifolius three chemical races were distinguished and a number of diosmetin glucoside malate esters detected. The flower flavonoid aglycone patterns of the nine Old World species surveyed differed markedly from the corresponding leaf profiles by the presence of flavones: luteolin and apigenin in eight and chrysoeriol in seven species as major constituents, while flavone C-glycosides were found only in trace amount in three species. In a leaf flavonoid survey of 13 representative New World Lupinus taxa, glycoflavones were major leaf components, a variety of methylated flavones were identified and flavonols were absent. The presence of the novel 2′-hydroxyflavone in five New World species may indicate some evolutionary link with the rough seeded taxa of the Old World.     

Flavonoid chemistry of arceuthobium (viscaceae)

Flavonoid compounds from 36 of the 38 known taxa of the genusArceuthobium (dwarf mistletoes) were examined. The flavonoid chemistry of the genus is rather uniform, all taxa producing 3-O-glycosides of the flavonols quercetin and myricetin. No infraspecific chemical variation was encountered, and in those instances where subspecific taxa are recognized, their chemistry was uniform. At the subgeneric level, members of subgenusArceuthobium synthesize primarily glucosides, whereas galactosides are more common in subgenusVaginata. In two of the four Old World species of subgenusArceuthobium (A. juniperi- procerae andA. oxycedri) only myricetin 3-O-glucoside was detected. There are no absolute flavonoid differences between subgenera, sections, or series. On the other hand, flavonoids are useful in several instances at the species level. In several cases, chemical data lend support to the recognition of species which in the past have been considered doubtfully distinct on the basis of morphology.     

BIOCHEMICAL HETEROPHYLLY AND FLAVONOID EVOLUTION IN NORTH AMERICAN POTAMOGETON (POTAMOGETONACEAE)

Morphologically heterophyllous species of Potamogeton also commonly display biochemical heterophylly with respect to flavonoid compounds. Generally, floating leaves contain an assortment of flavonoids, whereas submersed leaves often exhibit reduced flavonoid profiles. In strictly submersed (homophyllous) species, two patterns occur. Linear-leaved species have few flavonoids and their biochemical profiles resemble those of submersed leaves of heterophyllous species. Broad-leaved homophyllous species possess flavonoid profiles more similar to those of the floating leaves of heterophyllous species. Numerical analysis of these chemical data is consistent with phylogenetic relationships within the genus derived independently on the basis of morphological and chromosomal data. Glycoflavones, which are probably maintained in floating leaves because of their UV filtering ability, exhibit the most pronounced biochemical heterophylly in Potamogeton. The lack of glycoflavones in submersed leaves of heterophyllous species and in linear-leaved homophyllous species is attributable to the ability of naturally colored water to significantly absorb harmful UV radiation. These observations provide strong support for earlier hypotheses suggesting the importance of flavonoid evolution in the conquest of exposed terrestrial habitats by plants.     

Disc-electrophoresis of albumin and globulin fractions from dormant achenes of Lasthenia

Albumin and globulin fractions were extracted from dormant seeds of all 20 taxa of Lasthenia. After disc-electrophoresis on basic 7% acrylamide gels, mean R_p values, coefficients of variation and 95% confidence intervals were computed for both types of protein bands. Dendrograms were produced using similarity coefficients, indicating interspecific affinities among the taxa which differ from the sectional taxonomy of the genus. Protein data concerning certain problematical relationships are compared with published taxonomical and chemical data.     

Intraspecific flavonoid variation

This review is concerned with variation of flavonoid patterns within species. Many examples of species with invariant flavonoid patterns are known; there are at least as many examples where complex arrays of pigments are known. Eight categories of variation are discussed: 1) qualitatively invariant pigment profiles, 2) quantitative variation, 3) flavonoid races that do not correspond to recognized taxonomic groups, 4) flavonoid races that do correspond to recognized taxonomic groups, 5) flavonoid profile differences between different ploidy levels, 6) differences between organs or between tissues, 7) differences between developmental stages, and 8) environmentally influenced flavonoid profiles. These types of variation seem to occur randomly in the plant kingdom. Members of the same family, or in some cases, the same genus, can display different types of variation. Careful attention to these sources of variation is necessary before flavonoid characters can be used in taxonomic studies.     

Flavonoid chemistry and angiosperm evolution

A consideration of the distribution of flavonoid compounds in angiosperms indicates that exceptions exist to current thought on the presence of particular structural types occurring in primitive versus advanced flowering plants. As additional thorough survey work is done, the exceptions become increasingly common and the generalizations are weakened. A methodological problem in flavonoid surveys concerns documenting the “absence” of particular compounds and the question of quantitative versus qualitative variation of certain constituents. Consideration of flavonoid biosynthesis suggests that simple genetic differences likely control the classes of compounds present and this in turn indicates that caution be used in placing phylogenetic significance on such differences. Features of floral morphology used in studying angiosperm phylogeny have a complex genetic-developmental basis as compared to the genetic factors governing the presence of various flavonoid classes. This ostensibly is an important factor in explaining why reversals in certain trends of floral morphology are rarely noted and why these features are usually constant at higher taxonomic levels. By contrast, variation of flavonoid classes (by virtue of the small genetic differences controlling the presence of different classes) occurs at lower taxonomic levels. Genetic and enzymological studies of flavonoid biosynthesis also indicate that a single compound may be synthesized via different pathways, and this has significant implications for the use of flavonoid distribution in a phylogenetic sense. Given similar selection pressures, the same compounds may arise independently in distantly related plants. Clearly, this has occurred with floral anthocyanidins, where the distribution of particular compounds is related to pollinators. Flavonoid compounds will continue to be useful systematically at the generic level or lower, and possibly at the familial level in some instances. However, studies of the genetics and enzymology of flavonoid compounds in different groups of plants are needed if flavonoids are to be employed in a phylogenetic or evolutionary sense at higher taxonomic levels in the angiosperms. Much additional work in the difficult area of flavonoid functions is to be desired. Many more investigations of comparative flavonoid chemistry of fossil and extant members of what are considered the same genus must be carried out if any appreciation of flavonoid change through evolutionary time is to be achieved.     

Comparative phytochemistry of eleven species of Vigna (Fabaceae)

A survey of the biochemical constituents of 11 species of Vigna indicates the absence of the non-protein amino acid canavanine in their seeds, and absence of proanthocyanidin (polyphenol) in their leaves. Proanthocyanidin was found in the seeds of all, except Vigna subterranea. The constitutive leaf flavonoids of four genotypes of the pantropic V. subterranea were also studied and compared with those from three other cultivated species. The flavonoid kaempferol seems to be most prevalent as it was found in all of the four cultivated species and genotypes. The glycoside kaempferol-3-O-rutinoside was found present in the four genotypes of V. subterranea and other cultivated Vigna species. However, the flavonoid kaempferol-3-O-glucoside-7-rhamnoside is restricted to V. subterranea. This study questions the inclusion of V. subterranea in the genus Vigna on account of absence of seed proanthocyanidin and restricted accumulation of kaempferol-3-O-glucoside-7-rhamnoside in the leaves.     

Negatively charged flavones and tricin as chemosystematic markers in the palmae

A survey of 125 species of the Palmae revealed a complex pattern of flavonoids in the leaf. C-Glycosylflavones, leucoanthocyanins and tricin, luteolin and quercetin glycosides were common, being present in 84, 66, 51, 30 and 24% of the species respectively. Apigenin and kaempferol were recorded in only a few species and isorhamnetin only once. Eighteen flavonoids were identified: the 7-glucoside, 7-diglucoside and 7-rutinoside of both luteolin and tricin, tricin 5-glucoside, apigenin 7-rutinoside, quercetin 3-rutinoside-7-galactoside, isorhamnetin 7-rutinoside, orientin, iso-orientin, vitexin, isovitexin and vitexin 7-O-glucoside. Many of the C- and O-flavonoid glycosides were present as the potassium bisulphate salts and negatively charged compounds were detected in 50% of the species. The distribution patterns are correlated with the taxonomy of the family in several ways. Thus, the Phoenicoideae and Caryotoideae have distinctive flavonoid patterns, there is evidence to support the separation of the subfamilies Phytelephantoideae and Nypoideae, and tricin is a useful marker at tribal level. At the generic level, Cocos is clearly separated from Butia, and other Cocoseae and Mascarena and Chamaedorea form well defined groups within the Arecoideae. A numerical analysis of these biochemical data, together with morphological characters, produces a new classification which suggests that the flavonoid data may have more systematic value than is indicated when they are applied to the traditional classification.     

Leaf flavonoid chemistry of Coreopsis (Compositae) section Palmatae

Examination of leaf flavonoids of all taxa ofCoreopsis sectionPalmatae revealed that most members synthesize an array of common flavone (mostly luteolin and apigenin) glycosides. Each diploid species or diploid member of a species is characterized by a particular ensemble of compounds. These taxa includeC. major, C. verticillata, C. pulchra, C. palmata, andC. tripteris. The latter species differs from all other taxa in producing flavonol (kaempferol and quercetin) glycosides and what appear to be 6-oxygenated compounds. Tetraploids ofC. verticillata exhibit the same flavonoids as diploid members of the species, thus flavonoid chemistry supports the hypothesis that they originated from diploids within the species. Certain populations of hexaploid and octoploidC. major are similar chemically to diploids, suggesting they also originated as intraspeciflc polyploids. Other populations of these polyploids exhibit a flavonoid profile which differs from the profile of the diploids, and this profile is nearly identical to the octoploidCoreopsis × delphinifolia. The latter taxon has been viewed by Smith (1976) and Mueller (1974) as an interspecific hybrid betweenC. verticillata andC. major and/orC. tripteris. Species-specific compounds from the former species occur inC. × delphinifolia but no compounds unique to either of the latter two species are discernable. Flavonoid chemistry is not useful in ascertaining whether either or both species have been involved withC. verticillata in producing plants referable toC. × delphinifolia. There is morphological intergradation between octoploidC. major andC. × delphinifolia, and all plants not appearing to be “pure”C. major exhibit a flavonoid chemistry likeC. × delphinifolia. All plants of sectionPalmatae considered to be alloploids (includingC. × delphinifolia) produce the same array of leaf flavonoids, including several “novel” compounds not expressed in the putative parental taxa. Two of the “novel” flavonoids are present in the geographically restricted diploidC. pulchra. The systematic and phylogentic significance of this is not readily apparent.     

Geographical differentiation inferred from flavonoid content between coastal and freshwater populations of the coastal plant Lathyrus japonicus (Fabaceae)

Lake Biwa, one of the few ancient lakes in the world, harbors many coastal species that commonly inhabit seashores. The beach pea (Lathyrus japonicus) is a typical coastal species of this freshwater lake, and morphological and genetic differentiation between inland and coastal populations of this species have been reported. Inland and coastal habitats inflict distinct environmental stresses to plants, the latter imposing salt stress and high-light intensity, which leads to physiological differentiation. These abiotic stresses affect phenolic compounds, which play an important role in the response of plants to the toxic by-products of stress metabolism. We investigated physiological differentiation of phenolic compounds of the beach pea between inland and coastal habitats using high-performance liquid chromatography (HPLC) analysis. Flavonoid composition analyses revealed that patterns of flavonoid composition of inland populations at Lake Biwa were differentiated from those of coastal populations. All Lake Biwa individuals were fixed in the same flavonols glycosylated at 3- and 7-positions. In contrast, most coastal individuals contained flavonols glycosylated at 3-position alone, and these populations exhibited higher variation in flavonoid composition compared to among/within inland populations. Variation was likely lower in inland populations because of a bottleneck during landlocked periods, which is consistent with previous phylogeographic studies. A qualitative HPLC survey of flavonoid content revealed substantial variation among individuals regardless of locality. These results suggest that changes in the habitat environment may have led to beach pea acclimation via alteration of the quantity and quality of flavonoids.     

Phenolics from the culms of five bamboo species in the Tangjiahe and Wolong Giant Panda Reserves,Sichuan, China

Phenolic compounds were studied in the culms of five bamboo species collected in China: Yushania chungii, Fargesia robusta, Fargesia denudata, Fargesia rufa and Fargesia scabrida. All the species are eaten by giant panda (Ailuropoda melanoleuca). The culms contained phenolic acids and flavonoids in small concentrations, except for F. robusta, which did not contain flavonoids in detectable amounts. The species differed from each other in their phenolic composition. For example, F. rufa with the highest number of compounds clearly differed from other species. There were also differences among sampling sites, which reflect the differences among genotypes. Furthermore, there were clear ontogenetic differences in the culms: some compounds were present in mature culms but not in young (1–2 year old) culms, while the concentrations of other compounds decreased with increasing age. Over all, the composition and concentrations of soluble phenolic compounds in the bamboo culms were affected by species, age and site.