Flavonoids are a large and diverse group of compounds that, by their presence or absence, contribute greatly to wine quality. While the flavonoid content and composition of a wine reflects the vinification process to some extent, the primary determinant is the composition of the grapes at harvest. Thus, considerable research has been directed toward understanding the nature of flavonoids in grapevines, the factors that influence their biosynthesis, and how this knowledge might be used to manage and manipulate the flavonoid composition of berries at harvest. This review examines the flavonoids as a class of compounds, the role these compounds play in the plant, their contributions to wine quality, and recent research on the impacts of environmental factors and cultural practices on the flavonoid content and composition of grape berries.

Cultural Practice and Environmental Impacts on the Flavonoid Composition of Grapes and Wine: A Review of Recent Research

Statistical analyses of quantitative definitions of aromaticity, ASE (aromatic stabilization energies), RE (resonance energies), Λ (magnetic susceptibility exaltation), NICS, HOMA, I5, and AJ, evaluated for a set of 75 five-membered π-electron systems:  aza and phospha derivatives of furan, thiophene, pyrrole, and phosphole (aromatic systems), and a set of 30 ring-monosubstituted compounds (aromatic, nonaromatic, and antiaromatic systems) revealed statistically significant correlations among the various aromaticity criteria, provided the whole set of compounds is involved. Hence, broadly considered, the various manifestations of aromaticity are related and aromaticity can be regarded statistically as a one-dimensional phenomenon. In contrast, when comparisons are restricted to some regions or groups of compounds, e.g., aromatic compounds with ASE > 5 kcal/mol or polyhetero-five-membered rings, the quality of the correlations can deteriorate or even vanish. In practical applications, energetic, geometric, ...

To what extent can aromaticity be defined uniquely

Chemical protection plays a decisive role in the resistance of plants against pathogens and herbivores. The so-called secondary metabolites, which are a characteristic feature of plants, are especially important and can protect plants against a wide variety of microorganisms (viruses, bacteria, fungi) and herbivores (arthropods, vertebrates). As is the situation with all defense systems of plants and animals, a few specialized pathogens have evolved in plants and have overcome the chemical defense barrier. Furthermore, they are often attracted by a given plant toxin. During domestication of our crop and food plants secondary metabolites have sometimes been eliminated. Taking lupins as an example, it is illustrated that quinolizidine alkaloids are important as chemical defense compounds and that the alkaloid-free varieties (“sweet lupins”), which have been selected by plant breeders, are highly susceptible to a wide range of herbivores to which the alkaloid-rich wild types were resistant. The potential of secondary metabolites for plant breeding and agriculture is discussed.

Plant breeding: importance of plant secondary metabolites for protection against pathogens and herbivores

Thome, Robert F. (Rancho Santa Ana Botanic Garden, Claremont, CA 91711). Classification and geography of the flowering plants. Bot. Rev.58(3): 225–348. 1992.—This treatment of the flowering plants is the latest revision of my classification of the Class Angiospermae and replaces my 1983 and more recent 1992 synopses. An update is necessary because so much new information has been published in the last decade pertinent to the classification of the flowering plants. About 870 such recent books, monographs, and other botanical papers are cited in the Introduction, listed primarily by the botanical discipline that they represent. Also considerable changes in my classification have been necessitated by my narrowed family- and ordinal-gap concepts, acceptance of the ending “-anae” for superorders in place of the traditional but inappropriate “-iflorae,” and acceptance of more prior or more widely used names for the categories above the family. A new phyletic “shrub” replaces earlier versions, and attempts to indicate visually relative sizes and relationships among the superorders, orders, and suborders. One table includes a statistical summary of floweringplant taxa: ca. 233,900 species of 12,650 genera, 437 families, and 708 subfamilies and undivided families in 28 superorders, 71 orders, and 71 suborders of Angiospermae. Three other tables summarize the known indigenous distribution of the families and subfamilies of angiosperms about the world. The synopsis lists the flowering plant taxa from the class down to the subfamily (and in Asteraceae down to the tribe) with indication of the degree of confidence I place in the circumscription and placement of each category above the subfamily, the best available estimates of the number of genera and species for each category, and the known indigenous distribution of each subfamily and family. Table V lists alphabetically the geographical abbreviations used in the synopsis. The extensive bibliography of recent literature should be helpful to those persons interested in the classification of the flowering plants.

https://link.springer.com/content/pdf/10.1007/BF02858611.pdf

Classification and geography of the flowering plants

Accepting a commission to review progress in the subject embodied in our title is, perhaps, to take up something of a ‘poisoned chalice’. One of us, contributing on this same topic more than 20 years ago at the 1979 International Symposium on Aromaticity in Dubrovnik, wrote1 “A cynic would say that there are actually only two difficulties in discussing the subject of ‘aromaticity’ and ‘ring currents’sdeciding what is meant by ‘ring current’, and assigning a meaning to the term ‘aromaticity’!” That comment, though ostensibly facetious, had serious intent: it did encapsulate, with only a modicum of exaggeration, the problems that inherently beset any assessment such as the one attempted at Dubrovnik1 and in the present review. At the heart of the matter lies the undeniable fact that neither ring currents nor aromaticity are physical observables. Nevertheless, the intervening period has seen the ring-current idea, at least, become generally less controversial and more accepted than it once was. At the time of our opening quotation, one of us and Haigh had just published an exhaustive review2 of the ring-current concept covering the period up to about 1980sthe end of what might now be regarded as the era of semiempirical calculations in this field.2 This review2 (1979/1980) concluded that “the ‘ring current’ picture has proved itself ... to have great power in rationalising, at least qualitatively, the magnetic properties of π-electron systems. It is so pictorial that one can almost feel what is happening when a [conjugated] molecule is subjected to a magnetic field. Whatever advances the future may bring, it may be that the favourite habitat of the ‘ring current’ will be that in which it was born and brought up, namely, that of semi-empirical π-electron theory”. In other words, these authors were sanguine that, at the time (ca. 1980), the ring-current idea was gently coming to the end of its natural, useful life. However, as recently as 1997, when reviewing progress concerning the status of the ring-current model during the decade and a half or so after 1980s a period in this field that we have dubbed3 ‘the ab initio era’sthe present authors3 were initially somewhat surprised to find themselves concluding that “the ‘ring-current’ idea has well survived the first 15 years of the ab initio era.” Lazzeretti’s subsequent magnum opus4 on ring currents has more than confirmed this. By contrast, the sheer fact that in 2001sthe very first year of the 21st centurysthe American Chemical Society has seen fit to run this particular issue of Chemical Reviews shows that the concept of Aromaticity is as elusive as it ever was (see section II). There are three reasons for our not feeling obliged or inclined to present, in this review, an exhaustive, systematic, or historical critique of the ring-current concept itself. First, as we have just claimed, the idea of a ring current seems more secure now than it was 20 years ago, and it would appear that less apology or justification is needed for invoking it. Second, we ourselves have, in any case, only recently updated 1349 Chem. Rev. 2001, 101, 1349−1383

https://www.fc.up.pt/pessoas/jfgomes/documentos/ArtigosPDF/ChemRev,%20101,%201349-83(2001).pdf

Aromaticity and ring currents.

Feeding deterrency of flavonoids and related phenolics towards Schizaphis graminum and Myzus persicae: Aphid feeding deterrents in wheat

The feeding deterrency of a series of pyrrolizidine, indolizidine, and quinolizidine alkaloids and selected derivatives was measured against the pea aphid (Acyrthosiphon pisum Harris). The indolizidine alkaloid, castanospermine, was intensely active (ED50, 20 ppm) as were the quinolizidine alkaloids, but only modest feeding deterrency was observed with most of the pyrrolizidine alkaloids tested. The insect survival rate of aphids on a castanospermine-supplemented diet over 24 hr was also very low relative to the controls. Castanospermine does not inhibit aphid trehalase. The indolizidine alkaloid swainsonine occurred in the honeydew of pea aphid feeding on the locoweed,Astragalus lentiginosus. Since the pea aphid is a phloem feeder, swainsonine must be transported in the phloem.

Feeding deterrency of some pyrrolizidine, indolizidine, and quinolizidine alkaloids towards pea aphid (Acyrthosiphon pisum) and evidence for phloem transport of indolizidine alkaloid swainsonine

The probing behavior of biotype C of the greenbug, Schizaphis graminum (Rondani) on susceptible and resistant lines of sorghum, Sorghum bicolor (L.) Moench., was electronically monitored. Waveforms corresponding to salivation, phloem ingestion and non-phloem ingestion are described. The results of a parallel study revealed that the rate of population growth of S. graminum was significantly greater on susceptible lines of sorghum [i.e., NC + 70X. SC423 (Purple). SC423 (Tan)] than on resistant lines (i.e., TAM 2567, IS 809). Aphids probing the resistant lines of sorghum showed a significantly reduced imbibition of phloem sap compared with those aphids which fed on susceptible varieties. Also, increased numbers of separate probes and increased duration of non-probing were associated with greenbugs feeding on resistant lines. Greenbugs monitored on the nonhost plant, rice, exhibited non-phloem ingestion, but not phloem ingestion.



Resistance in sorghum to greenbugs is associated with the phloem. There appear to be no physial differences between the sorghum varieties in the location of or extent of lignification around the vascular bundles. Hence, resistance probably involves plant natural products associated with the phloem sap.



ZUSAMMENFASSUNG

Probeverhalten von Schizaphis graminum, Biotyp c an resistenten und anfalligen Sorghumsorten



Das Probeverhalten des Biotyps C von Schizaphis graminum (Rondani) an anfalligen und resistenten Klonen von Sorghum Sorghum bicolor (L.) Moench., wurde elektronisch registriert. Wellenfiguren fur den Speichelfluss, die Phloemaufnahme und − nichtaufnahme werden beschrieben. Die Ergebnisse eines Parallelexperiments zeigten, dass die Zuwachsrate von S. graminum bedeutend grosser war an anfalligen Klonen [NC + 70X, SC423 (Purpur), SC423 (Beige)] als an resistenten Klonen (TAM 2567, IS 809). Blattlause an resistenten Klonen saugten wahrend bedeutend kurzerer Zeit Phloemsaft als Blattlause an anfalligen Klonen. Ferner ergab sich eine grossere Zahl Probestiche und eine langere Dauer des Nichtprobens. Blattlause, welche an der Nichtwirtspflanze Reis beobachtet wurden, nahmen Nichtphloemsubstanz aber keinen Phloemsaft auf.



Resistenz von Sorghum gegen Sch. graminum steht in Zusammenhang mit dem Phloem. Offenbar gibt es keine physikalischen Unterschiede zwischen den Sorghumklonen in Bezug auf die Verteilung und die Verholzung der Gefassbundel. Daher muss die Resistenz wahrscheinlich mit Inhaltsstoffen des Phloemsafts zusammenhangen.

Probing behavior of the greenbug (schizaphis graminum, biotype c) on resistant and susceptible varieties of sorghum

Improvements in a synthetic diet for use in a bioassay to screen for feeding deterrents againstSchizaphis graminum, greenbug, are reported. Feeding on the synthetic diet was highly pH dependent with maximum feeding occurring at about pH 8.0. The bioassay was used as a guide in the isolation of feeding deterrent substances from aphid-resistant lines of sorghum (Sorghum bicolor). The major greenbug feeding deterrents isolated from sorghum leaves wereP-hydroxybenzaldehyde (ED50 0.13%), dhurrin (ED50 0.16%), and procyanidin (ED50 0.08%).

David L. Dreyer

Papers

Feeding deterrency of flavonoids and related phenolics towards Schizaphis graminum and Myzus persicae: Aphid feeding deterrents in wheat

Feeding deterrency of some pyrrolizidine, indolizidine, and quinolizidine alkaloids towards pea aphid (Acyrthosiphon pisum) and evidence for phloem transport of indolizidine alkaloid swainsonine

Probing behavior of the greenbug (schizaphis graminum, biotype c) on resistant and susceptible varieties of sorghum

Aphid feeding deterrents in sorghum : Bioassay isolation and characterization.

Evolution of limonoids in the Meliaceae