Disease Resistance in Higher Plants The Concept of Pre‐infectional and Post‐infectional Resistance

Publisher Summary It is the geoscience of coals, that is, their geochemistry of origin and postburial geological history, that suggests that coals are a very diverse set of materials. This chapter discusses the relations between the chemistry of coal macerals and reviews the biochemistry of their precursors and the biological markers in coals that are indicative of their origins. The content of carboxyl groups in coals is commonly determined by an ion-exchange reaction with barium acetate. Values of 1–4 milliequivalents per gram have been found for lignites and lower-rank subbituminous coals—decreasing with increasing rank and essentially zero for coals of higher rank—except that HVC coals of the Rocky Mountain province may contain some carboxyl. The cations in the carboxylates of low-rank coals can give rise to calcite deposits in liquefaction reactors, can promote liquefaction, and can give rise to catalysts for the gasification of lignite chars.

An Essay on the Organic Geochemistry of Coal

This review article presents 342 aromatic glycosides, isolated from and identified in plants and microorganisms, that demonstrate different biological activities. They are of great interest, especially for the medicinal and/or pharmaceutical industries. These biologically active natural sufactants are good prospects for the future chemical preparation of compounds useful as antioxidant, anticancer, antimicrobial, and antibacterial agents. These glycosidic compounds have been classified into several groups, including simple aromatic compounds, stilbenes, phenylethanoids, phenylpropanoids, naphthalene derivatives, and anthracene derivatives.

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Astonishing diversity of natural surfactants: 5. Biologically active glycosides of aromatic metabolites.

Phenolic glycosides have been the subject of considerable interest in recent ecological and systematic studies, especially those involving the Salicaceae But these compounds are markedly labile in aqueous media, and the consequences of spontaneous degradation for valid interpretation of results have been largely ignored by researchers We found that freeze-drying and oven-drying of leaf samples from several Populus and Salix species produced dramatic changes in the total and relative concentrations of specific phenolic glycosides, when compared to analyses of fresh material Extraction in aqueous and alcoholic media for extended (24 h) periods also effected changes in glycoside concentrations Alterations in phenolic glycoside concentrations, interconversions among glycosides, and production of artifactual glycosides result from a series of hydrolytic reactions These deleterious effects can be best (but not entirely) avoided by the use of fresh plant material, cold, nonaqueous extraction solvents, and short extraction times Because individual phenolic glycosides exhibit very different biological activities against herbivores, we caution ecologists to use utmost care in the performance and interpretation of phenolic glycoside assays

Chemical analysis of phenolic glycosides: Art, facts, and artifacts

The nonanthocyanin flavonoids of the diploids Phlox pilosa ssp. pilosa and P. drummondii ssp. mcallisteri and their putative allotetraploid derivatives P. aspera and P. villosissima were characterized by chromatographic and spectrophotometric analyses. Synthetic F1 diploid hybrids were also examined. All but one of the compounds encountered were glycoflavone (Cglycosyl) derivatives of either apigenin or luteolin. Although some compounds were present in all four taxa, most were species-specific. Together, the diploids exhibited 15 different flavonoids. Half of each tetraploid ensemble was composed of novel flavonoids, compounds not manifest in either diploid ancestor. In total, the tetraploids produced seven different novel flavonoids. Five novel compounds differed from particular diploid compounds only in number or kind of oxygen-linked sugar substituents. Ostensibly, these five are either identical to diploid biosynthetic intermediates or share common precursors with related diploid end products. The mode of origin of all novel compounds is discussed.

Shirley M. Hopkinson

Papers

The chemistry and biochemistry of phenolic glycosides