Methods in Polyphenol Analysis

by Santos-Buelga, Celestino; Williamson, G.

• ISBN13: 9780854045808
• ISBN10: 0854045805
• Format: Hardcover
• Copyright: 2003-05-01
• Publisher: Royal Society of Chemistry

Summary

Polyphenols make a vital contribution to the colour, tanning, taste and astringency of so many of society's favourites - from the unique taste of the British cup of tea to a glass of red wine. Found widely in many foods of plant origin, polyphenols are also becoming increasingly recognised as antioxidants in the body, with action on long-term health and reduction in the risk of chronic disease. Due to the importance of polyphenols, it is vital to conduct accurate and sensitive analysis. Providing detailed state-of-the-art research, presented in a practical and effective way, Methods in Polyphenol Analysis looks at the latest techniques in this developing field and includes, among others: * New modern techniques, such as LC-MS, LC-NMR and LC-coulometric detection * Chemical and enzymatic synthesis of polyphenol conjugates * Characterization of oligomeric and polymeric tannins and complex polyphenols This timely publication is written by highly experienced practitioners in this field and will be invaluable to all academics and industrialists involved in phytochemistry, biochemistry and food science.

Table of Contents

Polyphenol Extraction from Foods	p. 1
Introduction	p. 1
Solvent Extraction	p. 1
Factors that Influence the Efficiency of Solvent Extraction	p. 2
Sample Preparation	p. 2
The Extraction Process	p. 3
Solvent Extraction Using Different pH Values	p. 4
Solvent Extraction of Anthocyanins	p. 5
Solvent Extraction of Flavan-3-ols	p. 5
Auxiliary Operations	p. 7
Microwave-assisted Extraction	p. 7
Solid-phase Extraction	p. 8
Fractionation of Phenolic Compounds	p. 8
Solid-phase Extraction of Anthocyanidins	p. 9
Solid-phase Extraction of Proanthocyanidins	p. 10
Supercritical Fluid Extraction	p. 11
Pressurized Liquid Extraction	p. 12
References	p. 12
Methods of Polyphenol Extraction from Biological Fluids and Tissues	p. 17
Introduction	p. 17
Primary Considerations	p. 18
Polyphenol Extraction	p. 18
Solvent Extraction	p. 18
Comparing Solvents for Extraction of Quercetin Conjugates	p. 18
Solid-phase Extraction	p. 32
Hydrolysis	p. 32
Acid Hydrolysis	p. 32
Enzymic Hydrolysis	p. 43
Particular Problems with Sulfate determination	p. 44
Storage of Samples	p. 45
Summary	p. 45
References	p. 46
Application of LC-MS for the Identification of Polyphenols	p. 48
Introduction	p. 48
Analysis of Anthocyanins and Derived Pigments	p. 49
Methodology	p. 50
Results	p. 51
Analysis of Catechins and Proanthocyanidins	p. 54
Methodology	p. 55
Results	p. 55
Analysis of Flavonols and Flavonol Metabolites	p. 57
Methodology	p. 58
Results	p. 58
Acknowledgements	p. 60
References	p. 60
The Use of HPLC with Coulometric Detection in the Analysis of Flavonoids in Complex Matrices	p. 63
Introduction	p. 63
Basics of Electrochemistry	p. 64
Principle of Coulometric Array Detection	p. 68
Determination of Analysis Conditions	p. 69
Sensitivity in Coulometric Detection	p. 71
Analysis of Flavonoids Using HPLC with Coulometric Array Detection	p. 72
Voltammetric Characteristics of Flavonoids	p. 73
Conditions of Analysis for Each Class of Flavonoid	p. 75
Specific Applications of Coulometric Array Detection in the Field of Flavonoid Bioavailability	p. 81
Specific Applications of Coulometric Array Detection in the Field of Food Analysis	p. 86
Use of Fingerprints	p. 86
Estimation of the Overall Antioxidant Capacity	p. 87
Conclusions	p. 90
Acknowledgements	p. 90
References	p. 90
On-line Identification of Flavonoids by HPLC Coupled to Diode Array Detection	p. 92
Introduction	p. 92
Anthocyanins	p. 95
RP-HPLC Elution Characteristics	p. 95
Spectral Characteristics	p. 99
Flavan-3-ols (Catechins, Proanthocyanidins, Condensed Tannins)	p. 102
Flavones and Flavonols	p. 109
Chromatographic Behaviour	p. 110
UV-visible Spectroscopy	p. 113
Flavanones, Dihydroflavonols and Isoflavonoids	p. 118
Flavanones	p. 118
Dihydroflavonols	p. 120
Isoflavonoids	p. 120
Chalcones and Aurones	p. 121
Chalcones	p. 121
Aurones	p. 122
Dihydrochalcones	p. 123
References	p. 124
Application of LC-NMR in the Structure Elicidation of Polyphenols	p. 128
Introduction	p. 128
Principle of Operation of LC-NMR	p. 131
Solvent Suppression	p. 131
Operation in the On-flow Mode	p. 131
Operation in the Stop-flow Mode	p. 133
Sensitivity	p. 134
Limitations	p. 134
Hardware Set-up	p. 134
Generalities on the [superscript 1]H-NMR of Polyphenols	p. 135
Strategies for the On-line Identification of Polyphenols	p. 136
Stop-flow LC-[superscript 1]H-NMR of the Flavonoids and Xanthones from Gentiana ottonis	p. 138
Stop-flow LC-[superscript 1]H-NMR with 2D Correlation Experiments for the Structure Elucidation of a Flavanone of Monotse englerii	p. 142
On-flow LC-[superscript 1]H-NMR Characterisation of the Isoflavone and Isoflavanone Constituents of Erythrina vogelii	p. 146
Preliminary LC-UV-DAD and High Resolution LC-APCI-Q-TOF-MS-MS Analyses	p. 147
Low-flow LC-NMR with Microfractionation	p. 147
LC-UV-DAD with Post-column Derivatisation	p. 148
Interpretation of the On-line Data	p. 148
Other Applications of LC- NMR for the Study of Polyphenols	p. 152
Conclusions	p. 153
References	p. 154
Polyphenols: Measurement and Calculation of Their Physical Chemistry Properties	p. 157
Introduction	p. 157
Free Radical Chemistry of Flavan-3-ols	p. 158
Generation of Phenoxyl Radical by Pulsed Radiolysis and Flash Photolysis	p. 158
Radiolytic Experiments on Simple Phenols	p. 160
Radiolytic Experiments on Flavan-3-ols	p. 161
Flash Photolysis Experiments on Selectively Protected Flavan-3-ols	p. 164
Acid-Base Properties of Flavan-3-ols	p. 167
Redox Properties of Flavan-3-ols	p. 169
Determination of Redox Potential of Phenol by Pulse Radiolysis	p. 169
Simple Phenols	p. 170
Polyphenols	p. 171
Determination of Redox Potential by Fast Cyclic Voltammetry on Selectively Protected Flavan-3-ols	p. 173
Conclusion and Perspectives: A New Insight into Antioxidative Properties of Flavan-3-ols	p. 174
References	p. 175
Enzymatic Synthesis of Quercetin Glucosides and Glucuronides	p. 177
Introduction	p. 177
Production of Quercetin Glycosides	p. 178
Preparation of Crude Onion Enzyme Extract	p. 178
Preparation of Crude Leek Enzyme Extract	p. 179
Enzymatic Synthesis of Quercetin Glycosides	p. 179
Enzymatic Synthesis of Radio-labelled Quercetin Glycosides	p. 181
HPLC Analysis for Flavonoids	p. 181
Production of Quercetin Glucuronides	p. 182
Production of Pig Liver Extract	p. 182
Enzymatic Synthesis of Flavonoid Glucuronides	p. 182
Enzymatic Synthesis of Radio-labelled Quercetin Glucuronides	p. 182
Liquid Chromatography-Mass Spectrometry (LC-MS)	p. 183
HPLC Analysis for Flavonoids	p. 185
Concluding Remarks	p. 185
Acknowledgements	p. 185
References	p. 185
Chemical Synthesis of Flavonoid Conjugates	p. 187
Introduction	p. 187
Strategies for the Preparation of Flavonoid Conjugates	p. 188
The Total Synthesis of Basic Structures	p. 188
The Hemisynthesis of Conjugates	p. 191
Typical Experimental Procedures	p. 204
2,4-Dihydroxyphenyl-4-hydroxybenzyl Ketone	p. 204
2,4,6-Trihydroxyphenyl-4-hydroxybenzyl Ketone	p. 204
Daidzein	p. 205
[omega]-Methoxyphoracetophenone	p. 205
3,4-Dihydroxybenzoyl Chloride	p. 205
3-Methylquercetin	p. 206
Daidzein 7-Sulfate Potassium Salt	p. 206
Quercetin 3-Sulfate	p. 207
Quercetin 3'-Sulfate	p. 207
Quercetin 7-[beta]-D-Glucuronide (and Quercetin 4'-[beta]-D-Glucuronide)	p. 207
Daidzein 7-Glucuronide	p. 208
Quercetin 3-O-[beta]-D-Glucuronide	p. 209
Isorhamnetin	p. 210
Rhamnetin	p. 210
4'-Methylcatechin and 3'-Methylcatechin	p. 211
References	p. 212
Quantitative Determination of Flavonols in Plant Foods and Biological Fluids	p. 214
Introduction	p. 214
Flavonols in Plant Foods	p. 215
UV Detection of Total Flavonols after Acid Hydrolysis	p. 215
UV Detection of Individual Flavonol Glycosides	p. 217
Flavonols in Biological Fluids	p. 220
Fluorescence Detection of Total Flavonols after Acid Hydrolysis	p. 221
Electrochemical Detection of Conjugated Flavonols and of Total Flavonols after Enzymatic Hydrolysis	p. 223
References	p. 227
Analysis and Purification of Catechins and Their Transformation Products	p. 229
Introduction	p. 229
Catechin and Related Compound Isolation	p. 229
Extraction	p. 230
Separation Protocols	p. 231
Physical Properties of Fresh Leaf Flavan-3-ols and Related Compounds	p. 233
NMR Spectroscopy of Fresh Leaf Flavan-3-ols and Related Compounds	p. 236
Flavan-3-ol Dimeric Oxidation Products	p. 238
Extraction	p. 239
Separation Protocols	p. 240
Physical Properties of Black Tea Dimeric Flavonoid Oxidation Products	p. 241
Flavan-3-ol Polymeric Oxidation Products	p. 246
Roberts Fractionation	p. 249
Theafulvin Fractionation	p. 254
Black Tea Fraction by Solvent Precipitation	p. 255
Determination of Total Polyphenols in Tea Using the Folin-Ciocalteu Reagent	p. 258
Reagents	p. 258
Apparatus	p. 258
Preparation of test sample	p. 259
Procedure	p. 259
HPLC Conditions for Flavan-3-ol Dimeric Oxidation Products	p. 261
Structures of Flavan-3-ol Dimeric Oxidation Products	p. 262
References	p. 265
Analysis and Purification of Proanthocyanidin Oligomers	p. 267
Introduction	p. 267
Extraction and Purification of Proanthocyanidin Oligomers	p. 269
Extraction	p. 270
Purification	p. 270
Characterization of Proanthocyanidin Oligomers	p. 271
Thiolysis	p. 271
Mass Spectrometry	p. 272
NMR	p. 273
Quantification of Proanthocyanidin Oligomers	p. 275
Colorimetric Methods	p. 275
Reversed-phase HPLC	p. 276
Normal-phase HPLC	p. 276
Detection	p. 278
Conclusion	p. 279
References	p. 279
Analysis of Polymeric Proanthocyanidins and Complex Polyphenols	p. 284
Introduction	p. 284
Structure of Proanthocyanidin Polymers and Tannin-like Compounds	p. 285
Proanthocyanidins	p. 285
Tannin-like Compounds	p. 286
Analysis and Characterization	p. 291
Extraction from Plant Tissues	p. 291
Sample Clean-up by Liquid-liquid or Solid-phase Extraction	p. 292
Fractionation According to Molecular Weight	p. 293
Quantitation and Characterization of Polymeric Tannins	p. 295
Conclusion	p. 306
References	p. 307
The Analysis and Characterization of Chlorogenic Foods and Other Cinnamates	p. 314
Introduction	p. 314
The Cinnamate Conjugates	p. 314
The Chlorogenic Acids	p. 314
Other Cinnamate Conjugates	p. 316
Cinnamate Transformation Products	p. 316
Analysis and Characterization	p. 317
Structure and Hydrophobicity	p. 317
Extraction from Plant Tissues	p. 318
Extraction from Animal Tissues	p. 319
Sample Clean-up by Solvent Partition and Solid-phase Adsorption	p. 320
Artefacts	p. 321
Hydrolysis/Saponification	p. 321
Availability of Authentic Standard Compounds	p. 321
Chromatography	p. 324
Spectroscopic and Other Physical Properties	p. 328
Mass Spectroscopy	p. 333
References	p. 333
Analysis of Anthocyanins	p. 338
Introduction	p. 338
Chemistry	p. 339
Structure	p. 339
Stability	p. 341
Methods of Analysis	p. 343
Extraction	p. 343
Isolation and Purification	p. 345
Detection and Identification	p. 349
Techniques of Hydrolysis	p. 352
References	p. 353
Analysis and Purification of Flavanones, Chalcones and Dihydrochalcones	p. 359
Introduction	p. 359
Extraction	p. 360
Chemical Transformation	p. 364
Chromatographic Analysis	p. 365
Isolation and Purification	p. 365
UV Spectroscopy	p. 366
Flavanones	p. 366
Chalcones	p. 367
Dihydrochalcones	p. 367
[superscript 1]H NMR Spectroscopy	p. 368
Flavanones	p. 368
Chalcones	p. 368
Dihydrochalcones	p. 368
HPLC-ESI (Electrospray Ionization) Mass Spectrometry	p. 368
References	p. 371
Subject Index	p. 372
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