Phenolic Compound Biochemistry

284 Pages·2007·2.3 MB·English

by  Wilfred Vermerris

Chapter title i

PHENOLIC COMPOUND BIOCHEMISTRY
Contents iii

PHENOLIC COMPOUND
BIOCHEMISTRY
By
WILFRED VERMERRIS
University of Florida, Gainesville, FL, U.S.A.

and

RALPH NICHOLSON
Purdue University, West Lafayette, IN, U.S.A.
iv Contents

A C.I.P. Catalogue record for this book is available from the Library of Congress.
ISBN-10 1-4020-5163-8 (HB)
ISBN-13 978-1-4020-5163-0 (HB)
ISBN-10 1-4020-5164-6 (e-book)
ISBN-13 978-1-4020-5164-7 (e-book)

Published by Springer,
P.O. Box 17, 3300 AA Dordrecht, The Netherlands.

www.springer.com

Printed on acid-free paper
All Rights Reserved
© 2006 Springer
No part of this work may be reproduced, stored in a retrieval system, or transmitted
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or otherwise, without written permission from the Publisher, with the exception
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Contents v

CONTENTS

PREFACE xi

CHAPTER 1
Families of Phenolic Compounds and Means of Classification

1. Definitions 1
2. Classification 2
3. Classes of phenolic compounds 3
3.1 Simple phenolics 3
3.2 Phenolic acids and aldehydes 4
3.3 Acetophenones and phenylacetic acids 4
3.4 Cinnamic acids 5
3.5 Coumarins 6
3.6 Flavonoids 7
3.6.1 Chalcones 8
3.6.2 Aurones 8
3.6.3 Flavonoids 9
3.6.3.1 Flavanones 10
3.6.3.2 Flavanonols 10
3.6.3.3 Leucoanthocyanidins 11
3.6.3.4 Flavones 12
3.6.3.5 Anthocyanidins and deoxyanthocyandins 12
3.6.3.6 Anthocyanins 15
3.7 Biflavonyls 15
3.8 Benzophenones, xanthones and stilbenes 16
3.9 Benzoquinones, anthraquinones and naphthaquinones 17
3.10 Betacyanins 17
3.11 Lignans 18
3.12 Lignin 20
3.13 Tannins 23
3.13.1 Condensed tannins 24
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3.13.2 Gallotannins 25
3.13.3 Ellagitannins 26
3.13.4 Complex tannins 29
3.14 Phlobaphenes 30
4. References 32

CHAPTER 2
Chemical Properties of Phenolic Compounds

1.1 The benzene ring 35
1.2 Planar versus non-planar bonds 38
1.3 The acidic nature of the phenolic hydroxyl group 38
1.3.1 The effects of substituents on acidity 39
1.3.2 Use of acidity in separations 40
1.4 Hydrogen bonding and the phenolic hydroxyl group 40
1.4.1 Intra- and inter-molecular hydrogen bonds 41
1.4.2 Stability of the hydrogen bond ring 41
1.5 Metal complexes 43
1.6 Esterification 45
1.7 Ethers and glycosides 47
1.8 Oxidation of the phenolic hydroxyl group 48
1.8.1 Auto-oxidation of phenolic compounds 48
1.8.2 Enzymatic oxidation of the phenolic hydroxyl group 50
1.8.2.1 E.C. 1.10.3 50
1.8.2.2 E.C. 1.14.18.1 53
1.8.2.3 E.C. 1.11.1. 53
1.9 Reactive oxygen species and antioxidants 58
2. References 61

CHAPTER 3
Biosynthesis of Phenolic Compounds

1. Introduction 63
2. Protein isolation and purification 64
3. Gene cloning strategies 67
3.1 Insertional mutagenesis 70
3.2 Map-based cloning 72
3.3 The candidate-gene approach 72
3.4 QTL mapping 73
4. Isolation and characterization of recombinant proteins 74
5. Carbohydrate catabolism 76
5.1 Glycolysis 77
5.2 The pentose phosphate pathway 77
6. The shikimate pathway 81
Contents vii

7. The general phenylpropanoid pathway 84
8. Biosynthesis of phenolic acids 86
8.1 Salicylic acid 86
8.2 Gallic acid 88
9. Biosynthesis of flavonoids and condensed tannins 90
9.1 Structural genes and enzymes 90
9.2 Regulatory genes 96
10. Monolignol biosynthesis 102
11. Lignan biosynthesis 107
12. Lignin biosynthesis 112
12.1 Genetic control of lignification 112
12.2 Monolignol transport and polymerization 116
12.3 Modification of lignin for agro-industrial applications 120
12.3.1 Pulp and paper industry 121
12.3.2 Forage and silage quality 123
12.3.3 Ethanol production from ligno-cellulosic biomass 124
13. Hydroxycinnamic acid biosynthesis 125
14. Biosynthesis of sinapoyl esters 126
15. Coumarin biosynthesis 129
16. Stilbene biosynthesis 129
17. Biosynthesis of gallotannins and ellagitannins 130
18. References 134

CHAPTER 4
Isolation and Identification of Phenolic Compounds

1. Introduction 151
2. Isolation of phenolic compounds 151
2.1 Total phenolic content: the Folin-Ciocalteu reagent 152
2.2 Determining the content of condensed tannins 154
2.2.1 The butanol-HCl assay 154
2.2.2 The vanillin assay 154
2.2.3 Precipitation of condensed tannins with formaldehyde 155
2.3 Determining the content of gallotannins 155
2.3.1 The potassium iodate assay 155
2.3.2 The rhodanine assay 156
2.4 Determining the content of ellagitannins 157
2.4.1 Nitrous acid oxidation 157
2.4.2 The NaNO /HCl assay 158
2
2.5 Determining lignin content 159
2.5.1 Klason lignin 160
2.5.2 Acid detergent lignin 161
2.5.3 Thioglycolic acid lignin 162
2.5.4 Acetylbromide lignin 164
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3. Identification and characterization of phenolic compounds 166
3.1 Thin layer chromatography 166
3.2 Liquid chromatography: HPLC and LC-MS 169
3.3 Gas chromatography 170
3.4 Methods for the identification of lignin subunit composition 171
3.4.1 The nitrobenzene oxidation 172
3.4.2 Thioacidolysis 173
3.4.3 Derivatiation Followed by Reductive Cleavage 176
3.4.4 Analytical pyrolysis 178
3.4.5 Nuclear magnetic resonance 178
3.4.6 Fourier-transform infrared spectroscopy and near 181
infrared reflectance spectroscopy
4. Visualization of phenolic compounds in planta using 183
histochemical stains
4.1 An overview of histochemical staining protocols 183
4.2 Visualizing plant-pathogen interactions involving phenolics 185
with histochemical stains
5. References 190

CHAPTER 5
Analysis of Phenolic Compounds with Mass Spectrometry

1. The principles of mass spectrometry 197
1.1 Ionization 197
1.2 Mass Analysis 198
1.3 Detectors 199
1.4 Sample introduction 200
2. New developments in mass spectrometry 202
2.1 Fast atom bombardment 202
2.2 Plasma desorption ionization 203
2.3 Electrospray ionization 204
2.4 Matrix-assisted laser desorption ionization 206
3. Quantitation 208
4. References 210

CHAPTER 6
The Role of Phenols in Plant Defense

1. Preformed antimicrobial and insecticidal metabolites 211
1.1 Chlorogenic acid 213
1.2 Phloridzin and phloretin 214
1.3 Cyanogenic glycosides 215
1.4 Tuliposides 216
1.5 Protocatechuic acid 217
Contents ix

1.6 Lignin 217
1.7 C-glycosyl flavones 217
2. Compounds formed in response to pathogen attack 222
2.1 3-Deoxyanthocyanidins 222
2.2 Pisatin 224
2.3 Stilbenes 224
2.4 Salicylic acid 225
2.5 Lignin 227
3. References 230

CHAPTER 7
Phenolic Compounds and their Effects on Human Health

1. Introduction 235
2. Antioxidant properties 237
3. Disease prevention 246
4. Activity against toxins 251
5. References 253

Appendix 257

Index 267
Contents xi

PREFACE
Phenolic compounds represent a large group of molecules with a variety
of functions in plant growth, development, and defense. Phenolic
compounds include signaling molecules, pigments and flavors that can
attract or repel, as well as compounds that can protect the plant against
insects, fungi, bacteria, and viruses. Most phenolic compounds are present
as esters or glycosides rather than as free compounds. Tannins and lignin are
phenolic polymers. Tannins are used comercially as dyes and astringents,
and lignin accounts for structural ridgidity of cells and tissues and is
essential to vascular development. From this brief overview it is apparent
that phenolic compounds make up a large and fascinating family.

Our intention is to provide the reader with an overview of this family of
compounds that will show their diversity and provide a basis for continued
investigations. The target audience is intended to include phytopathologists,
botanists, agronomists, entomologists, and people with a general interest in
plant biochemistry. This book will also be a valuable resource when used as
a textbook in a course on phenolic compounds, aimed at advanced
undergraduate or beginning graduate students in the life sciences. While
writing this book we assumed the reader would have basic knowledge of
organic chemistry, biochemistry of DNA, RNA, proteins and lipids, and cell
physiology. At the end of the chapters we have provided some additional
references for further reading, either to obtain background information, or to
obtain more details.

The focus of this book is centered on structure, nomenclature and
occurrence of phenolic compounds (Chapter 1), and their chemical
properties (Chapter 2). Chapter 3 describes the biosynthetic pathways
leading to the major classes of phenolics. This chapter presents an up-to-date
overview of the genetic approaches that have been used to elucidate these
pathways. Chapter 4 presents an overview of methods for the isolation and
identification of plant phenolic compounds. Given that much of the recent
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