Physical Science

In addition to accumulating biologically active chemicals, plant roots continuously produce and secrete compounds into their immediate rhizosphere. However, the mechanisms that drive and regulate root secretion of secondary metabolites are not fully understood. To enlighten two neglected areas of root biology, root secretion and secondary metabolism, an in vitro system implementing root-specific elicitation over a 48-day time course was developed. After roots of Arabidopsis thaliana had been elicited with salicylic acid, jasmonic acid, chitosan, and two fungal cell wall elicitors, the secondary metabolites subsequently secreted were profiled. High-performance liquid chromatography was used to metabolically profile compounds in the root exudates, and 289 possible secondary metabolites were quantified. The chemical structures of 10 compounds were further characterized by 1 H and 13 C NMR: butanoic acid, trans-cinnamic acid, o-coumaric acid, p-coumaric acid, ferulic acid, phydroxybenzamide, methyl p-hydroxybenzoate, 3-indolepropanoic acid, syringic acid, and vanillic acid. Several of these compounds exhibited a wide range of antimicrobial activity against both soil-borne bacteria and fungi at the concentration detected in the root exudates.

Bioassay-directed fractionation for Staphylococcus aureus multidrug resistance efflux pump inhibitors resulted in isolation of novel acylated neohesperidosides from Geranium caespitosum. The more highly acylated compounds had no direct activity against S. aureus, but potentiated activity of the antibiotics berberine, rhein, ciprofloxacin and norfloxacin. Cellular concentrations of berberine were greatly increased in the presence of active esters. #

. xiv + 1237 pp. 7 × 10 1 /4 in. $249.95. ISBN 0-8493-2021-6. This excellent and timely volume on flavonoids provides a comprehensive update to the last compendium on the subject, The FlaVonoids-AdVances in Research Since 1986, edited by the late J. B. Harborne and published over a decade ago. This new book consists of 17 chapters covering more than 7000 structures in various flavonoid classes. In the preface the editors provide a brief but very interesting overview of the historic advances in the flavonoid arena. Accordingly, the choice of themes for the 17 chaptersswritten by authorities in the fieldsprovides good coverage of the area and gives the reader excellent overviews of particular topics in flavonoid research. Chapter 1 presents a brief, unified summary of general methods for extraction and preparative separation of the main categories of flavonoids. It also contains a section on analytical methods to establish chemical profiles and content of flavonoid in herbal drugs and useful tables and illustrations. The major emphasis of this chapter is the application of stand-alone and coupled HPLC. Chapter 2 reviews the different spectroscopic techniques used during the last decade for flavonoid identification. Examples of the usefulness and recent applications of different NMR techniques are emphasized, including the application of new 2D and 3D NMR techniques. This chapter provides a great deal of valuable information summarized in six tables (Tables 2.1-2.7) containing assigned 1 H and 13 C chemical shifts characteristic of the various flavonoid classes. The chapter also contains a discussion on mass spectrometry instrumentation and techniques, including coupled methods involving mass spectrometry for the analysis of flavonoids; several tables summarize the most relevant information (Tables 2.8-2.13). Recent applications of CD, IR, and UV spectrometric techniques are also treated in this chapter. Finally, an entire section is devoted to the colorimetric analyses of flavonoids. Chapter 3 deals with molecular biology and biotechnology of flavonoid biosynthesis. The advances in this topic are well summarized throughout the chapter, which provides a complete list of over 50 flavonoid biosynthetic enzymessfor which cDNA or genes are availablesand the transcription factors that regulate flavonoid biosynthetic genes for 12 plant species. At the end of the chapter there is an extensive listing of published examples of genetic modifications on flavonoid production by introduction of genes encoding transcription factors that regulate flavonoid biosynthetic genes. Chapter 4 offers an unpublished food composition database for flavonols, flavones, procyanidins, catechins, and flavanones. This database can be used to estimate flavonoid intake of populations, identify dietary sources of flavonoids, and assess associations between flavonoid intake and disease. Valuable information is provided in several tables included throughout the chapter and in Appendix 2. Chapter 5 covers newly acquired data on flavonoid composition and distribution in grapes and on flavonoid reactions in wine and structures of the resulting products. Chapter 6 records recent changes in the perceived role of flavonoids as health-promoting dietary antioxidants and places these observations in a broader context embracing other dietary phenols and mechanisms other than simple radical scavenging and radical suppression. The authors also describe the diversity of dietary polyphenols and tannins (PPT), the intake, absorption, metabolism, and pharmacokinetics of PPT, safety assessment, and future research requirements of PPT. In Chapter 7, the role of isoflavonoids in protecting human health is described. This chapter also provides useful information on metabolism and bioavailability of some isoflavonoids; their role in cancer prevention, including clinical studies; and their protective role against cardiovascular diseases, osteoporosis, cognitive decline, and menopausal symptoms. Chapter 8 reviews the experimental evidence and theoretical considerations supporting the main hypotheses about the functions of flavonoids in plants. The functions of colorful and colorless flavonoids are discussed; these include defense, photoprotection, protection against oxidative stress, and a role as chemical messengers. Chapter 9 provides a wide overview of flavonoid-protein interactions in man and their possible implications for human health. The specific topics include the biological significance of flavonoidprotein interaction in man, molecular interactions responsible for flavonoid-protein complexation, specificity of flavonoid-protein interactions, and examples of flavonoid-protein interactions in man. The remaining chapters cover recent advances in the most important groups of flavonoids, namely, anthocyanins (Chapter 10), flavans and proanthocyanidins (Chapter 11), flavones and flavanols (Chapter 12), flavone and flavonol O-glycosides (Chapter 13), C-glycosylflavonoids (Chapter 14), flavanones and dihydroflavonols (Chapter 15), new chalcones, dihydrochalcones, and aurones (Chapter 16), and bi-, tri-, tetra-, penta-, and hexaflavonoids (Chapter 17). Especially noteworthy in these chapters are the tables and appendixes listing naturally occurring flavonoids that were discovered since 1992. Entries in each table include plant source(s) and producing organ, complete chemical name, and references to the primary literature. In addition to the tables, some of the last chapters offer valuable information regarding the chemistry, production, localization in plant cells, and chemotaxonomy of the different types of flavonoids. Unfortunately, significant pharmacological properties of some types of flavonoids were not included. The book is well written and properly indexed and referenced (with literature coverage extending to 2004); in addition, all figures, tables, and chemical formulas are printed in a clear and consistent manner, although there are a few printing mistakes. In spite of these minor flaws, the volume is highly recommended to anyone interested in studying flavonoids from chemical, biochemical, pharmaceutical, nutraceutical, taxonomic, and economic points of view. It should also be in the library of any institution established for research in the areas of pharmacognosy, phytochemistry, and phytomedicine.

Dess-Martin periodinane oxidizes the 5'-hydroxyl group of adenosine analogues as exemplified with the case of cordycepin. The yield for the oxidation of cordycepin was almost quantitative in reproducible runs. This method for adenosine and its analogues is far more attractive than methodologies using EDC. HCl and DMSO, DCC and DCAA in DMSO, TPAP and NMO, CrO 3 in pyridine, DMSO with trichloroacetic anyhydride, or oxidations which proceed through either the oxime or the 1,3-diphenylimidazolidine derivative to furnish the aldehyde.

In addition to accumulating biologically active chemicals, plant roots continuously produce and secrete compounds into their immediate rhizosphere. However, the mechanisms that drive and regulate root secretion of secondary metabolites are not fully understood. To enlighten two neglected areas of root biology, root secretion and secondary metabolism, an in vitro system implementing root-specific elicitation over a 48-day time course was developed. After roots of Arabidopsis thaliana had been elicited with salicylic acid, jasmonic acid, chitosan, and two fungal cell wall elicitors, the secondary metabolites subsequently secreted were profiled. High-performance liquid chromatography was used to metabolically profile compounds in the root exudates, and 289 possible secondary metabolites were quantified. The chemical structures of 10 compounds were further characterized by 1 H and 13 C NMR: butanoic acid, trans-cinnamic acid, o-coumaric acid, p-coumaric acid, ferulic acid, phydroxybenzamide, methyl p-hydroxybenzoate, 3-indolepropanoic acid, syringic acid, and vanillic acid. Several of these compounds exhibited a wide range of antimicrobial activity against both soil-borne bacteria and fungi at the concentration detected in the root exudates.

This excellent and timely volume on flavonoids provides a comprehensive update to the last compendium on the subject, The FlaVonoids-AdVances in Research Since 1986, edited by the late J. B. Harborne and published over a decade ago. This new book consists of 17 chapters covering more than 7000 structures in various flavonoid classes. In the preface the editors provide a brief but very interesting overview of the historic advances in the flavonoid arena. Accordingly, the choice of themes for the 17 chaptersswritten by authorities in the fieldsprovides good coverage of the area and gives the reader excellent overviews of particular topics in flavonoid research. Chapter 1 presents a brief, unified summary of general methods for extraction and preparative separation of the main categories of flavonoids. It also contains a section on analytical methods to establish chemical profiles and content of flavonoid in herbal drugs and useful tables and illustrations. The major emphasis of this chapter is the application of stand-alone and coupled HPLC. Chapter 2 reviews the different spectroscopic techniques used during the last decade for flavonoid identification. Examples of the usefulness and recent applications of different NMR techniques are emphasized, including the application of new 2D and 3D NMR techniques. This chapter provides a great deal of valuable information summarized in six tables (Tables 2.1-2.7) containing assigned 1 H and 13 C chemical shifts characteristic of the various flavonoid classes.

Bioassay-directed fractionation for Staphylococcus aureus multidrug resistance efflux pump inhibitors resulted in isolation of novel acylated neohesperidosides from Geranium caespitosum. The more highly acylated compounds had no direct activity against S. aureus, but potentiated activity of the antibiotics berberine, rhein, ciprofloxacin and norfloxacin. Cellular concentrations of berberine were greatly increased in the presence of active esters.