Dale M. Smith

Xanthones in the Appalachian Asplenium complex

Abstract Four gold-fluorescent compounds earlier noted in members of the Appalachian Asplenium complex have now been identified from A. montanum as the C -glycoxanthones, mangiferin, isomagniferin, and their O -glucosides. The importance of these compounds as taxonomic markers in this group of ferns is discussed. The chromatographic profile of the plant known as A. stotleri is shown to be identical to A. bradleyi , which is further evidence that the two are conspecific.

Correlations between anthocyanin chemistry and pollination ecology in the Polemoniaceae

Abstract A study of the anthocyanins in a representative sample (34 species from 14 genera) of Polemoniaceae has shown that the pigment type in the flowers is broadly correlated with pollination ecology. Thus, hummingbird pollinated species such as Ipomopsis aggregata generally contain pelargonidin sometimes with cyanidin, while bee and beefly pollinated species (e.g. Gilia latiflora ) contain mainly delphinidin. On the other hand, lepidopteran species such as Leptodactylon californicum have cyanidin or mixtures of cyanidin with delphinidin. The above three anthocyanidins occur usually as the 3-glucoside, 3,5-diglucoside, 3-(p- coumarylglucoside ) and 3-(p- coumarylglucoside )-5- glucoside , although other types are occasionally found. The distribution of glycosidic types and of acylation, unlike that of the anthocyanidins, is more closely correlated with systematic position than with pollinating vectors. In autogamous species where animal pollination is absent or unimportant, anthocyanin pigmentation in the flowers retains the complexity present in related animal-pollinated taxa. Anthocyanins were also identified in hummingbird pollinated plants from two related families and pelargonidin derivatives were detected. In Fouquieria splendens (Fouquieriaceae), the glycosidic pattern was different from that in Polemoniaceae in being 3-galactoside. In Penstemon (Scrophulariaceae) a study of flower anthocyanins was consistent with Straws hypothesis that the wasp-pollinated P. spectabilis originated by hybridization between the hummingbird-pollinated P. centranthifolius and the bee-pollinated P. grinnellii .

Species-specific kaempferol derivatives in ferns of the appalachian Asplenium complex

Abstract A series of kaempferol derivatives have been identified in fronds of three parental species of the Appalachian Asplenium complex. Asplenium platyneuron is characterised by the presence of the 7-glucoside of kaempferol 3,4′-dimethyl ether and also contains kaempferol 3,7-diglucoside, free and with an aliphatic acyl attachment. By contrast, A. rhizophyllum contains a remarkable caffeoyl complex of kaempferol glycosides, which appears to be chromatographically homogenous. However, on deacylation, the complex yields caffeic acid and the 7-glucoside, 3,7-diglucoside, 3-sophoroside-7-glucoside and 7,4′-diglucoside of kaempferol. Asplenium montanum , in addition to having previously characterised glycosylxanthones, has two further kaempferol derivatives. It has been confirmed that these various species specific flavonoids are inherited in an additive fashion in three interspecific hybrids.

Anthochlors and other flavonoids as honey guides in the compositae

Anthochlor pigments have been recorded for the first time in three species of Helianthus and in Viguiera laciniata. Yellow flavonols based on quercetagetin or gossypetin have been found in yellow flowered species of Eriophyllum and Geraea. In Eriophyllum, all seven species studied contain quercetagetin and/or patuletin 7-glucosides. In those species containing UV honey guides, either yellow flavonoid or colourless quercetin glycosides can be responsible for producing strongly UV absorbent zones on the flowers. Thus in Helianthus, honey guides in some species result from UV absorbance by the chalcone coreopsin and the aurone sulphurein, whilst in H. annuus they result from absorbance by quercetin 3- and 7-glucosides. Furthermore, the occurrence of yellow flavonoids in flowers is not directly correlated with the presence of UV nectar guides. A detailed study of the distribution of chalcone in Coreopsis bigelovii flowers revealed that the anthochlor was present in epidermal cells on both upper and lower surfaces.

Flavonoids from chemotypes of the goldback fern, Pityrogramma triangularis

Abstract More than 20 flavonoid aglycones were identified from the frond exudate of various collections of Pityrogramma triangularis . Ten of them are novel natural products; most of the others are rare flavonoids. They are substituted at C-8; many are C -methylated. They mostly occur only as trace constituents in var. triangularis . Two compounds come from var. viscosa . One population of P. triangularis var. triangularis exhibits a unique flavonoid pattern not encountered before in any other chemotype studied.

Flavonoid diversification in the polemoniaceae

Abstract Analysis of species representing most sections of all the genera in the family Polemoniaceae showed a range of variation in flavonoids comparable to variation already documented for gross morphological features, karyotypes and pollen grains. Three main groups of flavonoids predominate: (A) common flavonols (kaempferol, quercetin, myricetin); (B) 6-methoxyflavonols (patuletin, eupalitin, eupatolitin); and (C) C -glycosylflavones (apigenin and luteolin based). Cobaea, Loeselia], Polemonium, Allophyllum, Collomia and Gymnosteris have predominantly Group A flavonoids; Bonplandia, Ipomopsis and Eriastrum have predominantly Group B flavonoids; Phlox , Microsteris and Leptodactylon have predominantly Group C flavonoids; while the remaining genera ( Cantua, Huthia, Gilia, Langloisia, Navarretia and Linanthus ) either have flavonoids of all three groups, or some species within a genus have flavonoids of one group, while other species have flavonoids of another group. Linanthus, Gilia and Navarretia (3 of the larger genera in the family) show great flavonoid diversity, while Langloisia (4 species) has 2 species with Group A flavonoids and the other two species have Group B pigments. Two rare hydroxycoumarins, one being daphnetin, were detected in five genera but they proved to be only of limited systematic interest.

Identification of eupalitin, eupatolitin and patuletin glycosides in Ipomopsis aggregata

Abstract Eupalitin, eupatolitin and patuletin 3- O -galactosides as well as eupalitin and patuletin 3- O -diglucosides have been isolated and identified from Ipomopsis aggregata (Polemoniaceae). These 6-methoxylated flavonols are important taxonomic markers in the family, occurring as they do in nine of the eighteen known genera. Microscale methods of identifying these and other related highly substituted flavonols are discussed. Studies of the mass spectral fragmentation patterns have shown that quercetagetin derivatives methylated in the A-ring can be distinguished from similar compounds methylated in the B-ring and from the analogous gossypetin derivatives.

Honeybee Responses to Reward Size and Colour in an Artificial Flower Patch

SummaryWe describe an artificial flower patch suitable for quantitative ecological studies of plant-pollinator interactions. The number of flowers visited per trip by honeybees foraging on the patch was negatively dependent on mean nectar yield per flower in a logarithmic relationship. The relationship held whether all flowers provided reward or some were empty. Individual foragers on a mixed-colour patch of flowers were constant to one colour.

Flavonoid and ceroptin pigments from frond exudates of Pityrogramma triangularis

Abstract Two chemically distinct golden-yellow flavonoid exudates occur on the underside of fronds of Pityrogramma triangularis : ceroptin and a newly described flavonol, 6-methyl-8-methoxy-3,5,7-trihydroxyflavone were detected in one of the exudates and two methylated kaempferol derivatives, 4′-methoxy-3,5,7-trihydroxyflavone and 3,5-dihydroxy-7,4′-dimethoxyflavone were isolated from the other.

Leptodactylone, a yellow coumarin from Leptodactylon and Linanthus species

Abstract A new phenol in Leptodactylon and Linanthus leaf has been identified by spectral procedures as 5,7-dimethoxy-8-hydroxycoumarin. This structure has been confirmed by synthesis. Leptodactylone is unique among simple hydroxycoumarins in its yellow colour.