Antioxidant Polymers

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Phillip Carmical (pcarmical@scrivenerpublishing.com)

Antioxidant Polymers Synthesis, Properties,

and Applications

Edited by

Giuseppe Cirillo and

Francesca lemma Department of Pharmaceutical Sciences,

University of Calabria, Italy

Scrivener

WILEY

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Cover design by Russell Richardson

Library of Congress Cataloging-in-Publication Data:

ISBN 978-1-118-20854-0

Printed in the United States of America

10 9 8 7 6 5 4 3 2 1

Contents

Preface xv

List of Contributors xix

1. Antioxidants: Introduction 1 Chunhuan He, Yingtning Pan, Xiaowen Ji and Hengshan Wang 1.1 The Meaning of Antioxidant 1 1.2 The Category of Antioxidants and Introduction

of often Used Antioxidants 2 1.2.1 BHT 4 1.2.2 Quercetin 5 1.2.3 BHA 5 1.2.4 2-tert-Butylhydroquinone (TBHQ) 6 1.2.5 Gallic Acid 6 1.2.6 Resveratrol 6 1.2.7 Luteolin 7 1.2.8 Caff eic Acid 7 1.2.9 Catechin 7

1.3 Antioxidant Evaluation Methods 8 1.3.1 DPPH Radical Scavenging Assay 8 1.3.2 ABTS Radical Scavenging Activity 8 1.3.3 Phosphomolybdenum Assay 9 1.3.4 Reducing Power Assay 9 1.3.5 Total Phenols Assay by Folin-Ciocalteu

Reagent 10 1.3.6 Hydroxyl Radical Scavenging Assay 10 1.3.7 ß-carotene-linoleic Acid Assay 11 1.3.8 Superoxide Radical Scavenging Assay 11 1.3.9 Metal Ion Chelating Assay 12 1.3.10 Determination of Total Flavonoid Content 12

v

vi CONTENTS

1.4 Antioxidant and its Mechanisms 13 1.4.1 Mechanism of Scavenging

Free Radicals 13 1.4.2 Mechanism of Metal Chelating Properties 14

1.5 Adverse Effects of Antioxidants 15 References 16

2. Natural Polyphenol and Flavonoid Polymers 23 Kelly C. Heim 2.1 Introduction 23 2.2 Structural Classification of Polyphenols 24

2.2.1 Simple Phenolics 24 2.2.2 Stilbenes 26 2.2.3 Lignin 27 2.2.4 Flavonoids 28 2.2.5 Tannins 29

2.3 Polyphenol Biosynthesis and Function in Plants 34 2.3.1 Biosynthesis 34 2.3.2 Protective Roles 36

2.4 Tannins in Human Nutrition 36 2.4.1 Dietary Sources and Intake 36 2.4.2 Absorption and Metabolism 37

2.5 Antioxidant Activity of Tannins 41 2.5.1 Mechanisms 41 2.5.2 Structure-activity Relationships 44

2.6 Protective Effects of Proanthocyanidins in Human Health 45

2.7 Conclusion 46 Acknowledgements 46 References 47

3. Synthesis and Applications of Polymeric Flavonoids 55 Hiroshi Uyama and Young-Jin Kim 3.1 Introduction 55 3.2 Polycondensates of Catechin with Aldehydes 57 3.3 Enzymatically Polymerized Flavonoids 69 3.4 Biopolymer-flavonoid Conjugates 76 3.5 Conclusion 84 References 84

CONTENTS vii

4. Antioxidant Polymers: Metal Chelating Agents 87 Hiba M. Zalloum and Mohammad S. Mubarak 4.1 Introduction 87

4.1.1 Antioxidants 87 4.1.2 Natural Polymers as Antioxidants 88 4.1.3 Chelating Polymers and Heavy Metal Ions 90

4.2 Chitin and Chitosan 91 4.2.1 Chitin and Chitosan Derivatives 94 4.2.2 Chitin and Chitosan as Chelating Agents 95

4.3 Alginates 96 4.4 Chelation Studies 97

4.4.1 Chitosan Derivatives as Chelating Agents 101 4.4.2 Alginates as Chelating Agents 103

4.5 Conclusions 106 References 107

5. Antioxidant Polymers by Chitosan Modification 115 Jarmila Vinsovâ and Eva Vavfikova 5.1 Introduction 115 5.2 Chitosan Characteristics 117 5.3 Reactive Oxygen Species and Chitosan

as Antioxidant 117 5.4 Structure Modifications 120

5.4.1 N-Carboxymethyl Chitosan Derivatives 120 5.4.2 Quaternary Salts 121 5.4.3 Sulphur Derivatives 122 5.4.4 Chitosan Containing Phenolic Compounds 124 5.4.5 Schiff Bases of Chitosan 127

5.5 Conclusion 129 References 129

6. Cellulose and Dextran Antioxidant Polymers for Biomédical Applications 133 Sonia Trombino, Roberta Cassano and Teresa Ferrarelli 6.1 Introduction 133 6.2 Antioxidant Polymers Cellulose-based 134

6.2.1 Cellulose 134 6.2.2 Antioxidant Biomaterials

Carboxymethylcellulose-based 135 6.2.3 Ferulate Lipoate and Tocopherulate Cellulose 136

viii CONTENTS

6.2.4 Cellulose Hydrogel Containing Trans-f erulic Acid 138

6.2.5 Polymeric Antioxidant Membranes Based on Modified Cellulose and PVDF/cellulose Blends 139

6.2.6 Synthesis of Antioxidant Novel Broom and Cotton Fibers Derivatives 140

6.3 Antioxidant Polymers Dextran-based 142 6.3.1 Dextran 142 6.3.2 Biocompatible Dextran-coated Nanoceria

with pH-dependent Antioxidant Properties 143 6.3.3 Coniugates of Dextran with Antioxidant

Properties 145 6.3.4 Dextran Hydrogel Linking Tnms-ferulic

Acid for the Stabilization and Transdermal Delivery of Vitamin E 146

References 149

7. Antioxidant Polymers by Free Radical Grafting on Natural Polymers 153 Manuela Curcio, Ortensia Ilaria Parisi, Francesco Puoci, Ilaria Altimari, Untile Gianfranco Spizzirri and Nevio Picci 7.1 Introduction 153 7.2 Grafting of Antioxidant Molecules

on Natural Polymers 156 7.3 Proteins-based Antioxidant Polymers 157 7.4 Polysaccharides-based Antioxidant Polymers 164

7.4.1 Chitosan 164 7.4.2 Starch 166 7.4.3 Inulin and Alginate 170

7.5 Conclusions 175 Acknowledgements 176 References 176

8. Natural Polymers with Antioxidant Properties: Poly-/oligosaccharides of Marine Origin 179 Guangling Jiao, Guangli Yu, Xiaoliang Zhao, Junzeng Zhang and H. Stephen Ewart 8.1 Introduction to Polysaccharides

from Marine Sources 180

CONTENTS ix

8.1.1 Polysaccharides from Marine Algae 180 8.1.2 Polysaccharides from Marine Invertebrates 181 8.1.3 Marine Bacteria Polysaccharides 182

8.2 Antioxidant Activities of Marine Polysaccharides and their Derivatives 183 8.2.1 Antioxidant Evaluation Methods 183 8.2.2 Marine Sulfated Polysaccharides 187 8.2.3 Marine Uronic Acid-containing

Polysaccharides 188 8.2.4 Marine Non-acidic Polysaccharides

and their Oligomers 189 8.2.5 Marine Glycoconjugates 189

8.3 Applications of Marine Antioxidant Polysaccharides and their Derivatives 191 8.3.1 Applications in Food Industry 191 8.3.2 Applications as Medicinal Materials 191 8.3.3 Applications as Cosmetic Ingredients 192 8.3.4 Applications in Other Fields 193

8.4 Structure-antioxidant Relationships of Marine Poly- / oligosaccharides 193

8.5 Conclusions 195 Acknowledgements 195 References 195

9. Antioxidant Peptides from Marine Origin: Sources, Properties and Potential Applications 203 Begona Giménez, M. Elvira Lôpez-Caballero, M. Pilar Montero and M. Carmen Gomez-Guillen 9.1 Introduction 204 9.2 Whole Fish Hydrolysates 207 9.3 Marine Invertebrate Hydrolysates 223 9.4 Fish Frames Hydrolysates 227 9.5 Viscera Hydrolysates 228 9.6 Muscle Hydrolysates 232 9.7 Collagen and Gelatin Hydrolysates 240 9.8 Seaweeds Hydrolysates 243 9.9 Potential Applications 245 9.10 Conclusions 249 Acknowledgements 250 References 250

x CONTENTS

10. Synthetic Antioxidant Polymers: Enzyme Mimics 259 Cheng Wang, Gang-lin Yan and Gui-min Luo 10.1 Introduction 260 10.2 Organo-selenium/tellurium Compound Mimics 261

10.2.1 Chemistry of Organo-selenium/tellurium 261 10.2.2 Synthetic Organo-selenium/tellurium

Compounds as GPX Mimics 263 10.2.3 Cyclodextrin-based Mimics 272

10.3 Metal Complex Mimics 281 10.3.1 The Role of Metal Ions in Complexes 282 10.3.2 Manganese Complexes Mimics 283 10.3.3 Other Metal Complex Mimics 293

10.4 Selenoprotein Mimics 295 10.4.1 Strategies of Selenoprotein Synthesis 295 10.4.2 Synthetic Selenoproteins 305

10.5 Supramolecular Nanoenzyme Mimics 312 10.5.1 Advantages of Supramolecular

Nanoenzyme Mimics 313 10.5.2 Supramolecular Nanoenzyme Mimics

with Antioxidant Acitivity 314 10.6 Conclusion 325 References 325

11. Synthetic Polymers with Antioxidant Properties 333 Ashveen V. Nand and Paul A. Kilmartin 11.1 Introduction 334 11.2 Intrinsically Conducting Polymers 335 11.3 Intrinsically Conducting Polymers

with Antioxidant Properties 336 11.4 Synthesis of Antioxidant Intrinsically

Conducting Polymers 337 11.4.1 Chemical Synthesis 337 11.4.2 Electrochemical Synthesis 338 11.4.3 Other Polymerization Techniques 339

11.5 Polymer Morphologies 340 11.5.1 Polyaniline 340 11.5.2 Polypyrrole 342 11.5.3 Poly(3,4-ethylenedioxythiophene) 343

11.6 Mechanism of Radical Scavenging 344 11.7 Assessment of Free Radical Scavenging Capacity 346

11.7.1 DPPH Assay 347 11.7.2 ABTS Assay 347

CONTENTS xi

11.8 Factors Affecting the Radical Scavenging Activity 348 11.9 Polymer Blends and Practical Applications 350 References 351

12. Synthesis of Antioxidant Monomers Based on Sterically Hindered Phenols, a-Tocopherols, Phosphites and Hindered Amine Light Stabilizers (HALS) and their Copolymerization with Ethylene, Propylene or Styrene 355 Carl-Eric Wilén 12.1 Introduction 356 12.2 Synthesis of Antioxidant Monomers to Enhance

Physical Persistence and Performance of Stabilizers 361 12.2.1 Copolymerization of Antioxidants

with oc-Olefins Using Coordination Catalysts 363

12.2.2 Synthesis of Antioxidant Monomers 364 12.3 Phenolic Antioxidant Monomers and their

Copolymerization with Coordination Catalysts 369 12.3.1 Copolymerization of Antioxidant

Monomers with Ethylene or Propylene using Traditional Ziegler-Natta Catalysts 369

12.4 Copolymerization of Antioxidant Monomers with Ethylene, Propylene, Styrene and Carbon Monoxide Using Single Site Catalysts 372 12.4.1 Copolymerization of Phenolic Antioxidant

Monomers 372 12.4.2 Copolymerization of HALS Monomers

using Single Site Catalysts 376 12.5 Conclusions 379 Acknowledgements 380 References 380

13. Novel Polymeric Antioxidants for Materials 385 Ashish Dhawan, Vijayendra Kumar, Virinder S. Partnarand Ashok L. Cholli 13.1 Industrial Antioxidants 386 13.2 Antioxidants Used in Plastics (Polymer) Industry 386

13.2.1 Primary Antioxidants 388 13.2.2 Secondary Antioxidants 389

13.3 Antioxidants Used in Lubricant Industry 389

xii CONTENTS

13.4 Antioxidants Used in Elastomer (Rubber) Industry 390 13.5 Antioxidants Used in Fuel Industry 392 13.6 Antioxidants Used in Food Industry 393

13.6.1 Natural Food Antioxidants 393 13.6.2 Synthetic Food Antioxidants 394

13.7 Limitations of Conventional Antioxidants 395 13.7.1 Performance Issues because of Antioxidant

Efficiency Loss 395 13.7.2 Environmental Issues and Safety Concerns 395 13.7.3 Compatibility Issues 396 13.7.4 Poor Thermal Stability 396

13.8 Trends towards High Molecular Weight Antioxidants 396 13.8.1 Functionalization of Conventional

Antioxidants with Hydrocarbon Chains 397 13.8.2 Macromolecular Antioxidants 397 13.8.3 Polymer-bound Antioxidants 398 13.8.4 Polymeric Antioxidants 401

13.9 Motivation, Design and Methodology for Synthesis of Novel Polymeric Antioxidant Motivation 407 13.9.1 Design of the Polymeric Antioxidants 408 13.9.2 Methodology 408

13.10 Biocatalytic Synthesis of Polymeric Antioxidants 409 13.11 General Procedure for Enzymatic Polymerization 410

13.11.1 Synthesis and Characterization of Polymeric Antioxidants 411

13.11.2 Antioxidant Activity of Polymeric Antioxidants 417

13.11.3 Evaluation of Polymeric Antioxidants in Vegetable Oils by Accelerated Oxidation 420

13.12 Conclusions 421 Acknowledgement 422 References 422

14. Biopolymeric Colloidal Particles Loaded with Polyphenolic Antioxidants 427 Ashok R. Patel and Krassimir P. Velikov 14.1 Introduction 427 14.2 Polyphenols: Antioxidant Properties and Health

Benefits 428

CONTENTS xiii

14.3 Polyphenols: Formulation and Delivery Challenges 429 14.3.1 Solubility 430 14.3.2 Chemical Reactivity and Degradation 430 14.3.3 Stability in Physiological Conditions 430 14.3.4 First Pass Metabolism and

Pharmacokinetics 431 14.3.5 Organoleptic Properties and

Aesthetic Appeal 431 14.4 Polyphenols Loaded Biopolymeric

Colloidal Particles 431 14.4.1 Curcumin Loaded Biopolymeric

Colloidal Particles 433 14.4.2 Silibinin Loaded Biopolymeric

Colloidal Particles 441 14.4.3 Quercetin Loaded Biopolymeric

Colloidal Particles 447 14.5 Conclusion 454 References 455

15. Antioxidant Polymers for Tuning Biomaterial Biocompatibility: From Drug Delivery to Tissue Engineering 459 David Cochran and Thomas D. Dziubla 15.1 Introduction 459 15.2 Oxidative Stress in Relation to Biocompatibility 460

15.2.1 Mechanism of Immune Response 460 15.2.2 Examples in Practice 464

15.3 Antioxidant Polymers in Drug Delivery 467 15.3.1 Uses as Active Pharmaceutical Ingredients 467 15.3.2 Uses as Pharmaceutical Excipients 468

15.4 Antioxidant Polymers in Anti-cancer Therapies 470 15.5 Antioxidant Polymers in Wound Healing

and Tissue Engineering 472 15.5.1 Antioxidant Polymers Incorporated into

Biomaterials 472 15.6 Conclusions and Perspectives 476 References 479

Index 485

Preface

This book is a complete and detailed overview on the recent development in the field of polymeric materials showing antioxidant properties. The research area has grown rapidly in the last decade because antioxidant polymers combine the advantageous properties of both polymeric materials and antioxidants components.

The importance of antioxidant materials in biomedicine, bio-pharmaceutics, cosmetic and nutrition has been highlighted by various scientific reports including research articles, review articles, as well as book chapters, proving the link between oxi-dative stress and the development of several human pathologies such as cancer, cardiovascular and neurodegenerative diseases, atherosclerosis, and so on. On the other hand, advancements in synthesis techniques and processing technologies have trans-formed both natural and synthetic polymers into an integral part of everyday life, with importance from both production and application points of view in innovative technological and engineering processes.

Antioxidant polymers are a topic of great interest for researchers in many industrials fields: a large number of research groups have helped to develop various industrial divisions such as pharmaceu-tical, cosmetic and food industry, plastic materials industries and nano-engineering technology. Furthermore, the strong interest in these materials has stimulated the activity of botanic and marine researchers that have broadened the expertise in this context.

In materials science, antioxidant polymers are studied in terms of innovative and unique physical-chemical properties with particular emphasis to the stability behaviour as well as to the mechanical strength and long-time stability. Recent years have, indeed, witnessed significant progress in the development of effi-cient and tailor-made stabilizer compounds for various plastics, rubbers, elastomers and coatings to meet the needs of the multiple industrial sectors.

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xvi PREFACE

In the biomédical area, antioxidant conjugates of various poly-mers were synthesized in consideration of extension and amplifica-tion of the physiological properties. In particular, novel drugs (e.g. anticancer, synthetic enzymes) or pro-drugs, in which the active ingredient is a molecule showing antioxidant ability, were proposed; furthermore, new polymeric drug delivery systems and tissue scaf-folds have been prepared by co valent and/or non-co valent incor-poration of antioxidant molecules with the aim to increase the bio-compatibility and to reduce the living tissue side-effects. In the last cases, the antioxidant is required to overcome the side-effects recorded after the topic or systemic administration of the device.

Regarding the pharmaceutical and cosmetic industry, the interest in antioxidant polymers is related not only to their biological activity, but also to their ability to protect the whole formulation and its components from degradation. A considerable limitation in the use of some promising pharmaceutical and cosmetic formulation is often ascribed to the short-term stability of their components which leads to the reduction of their efficiency and, even worse, to the development of toxic side-effects.

Last but not least, it should also be mentioned that food science and technology show this to be an important breakthrough area. Antioxidant polymers are studied from both a nutritional and an industrial points of view with respect to new functional foods or materials for food packaging. The growing evidence about specific health benefits of natural polymeric products, coupled with the recent popularity of functional foods, has led to an increased inter-est among food scientists to characterize and incorporate them in food products. The presence of antioxidant compounds in food has a strong impact on human health and nutritional value, contrib-uting to the preservation quality of foods while in storage condi-tions. During storage, the nutritional behaviour of a food could be altered as a consequence of the interaction with atmospheric agents or packaging materials. To overcome these problems, an emerging field is the so-called "intelligent packaging", in which the materials employed for the production of the package are based on antioxi-dant polymers.

The whole of the above-mentioned application fields of antioxi-dant polymers are highlighted in this book. The contributors are researchers from top universities and research and development lab-oratories (from Europe, USA, Asia and Oceania) and their chapters give an exhaustive overview of the synthesis, characterization, and

PREFACE xvii

practical applicability of these materials. In the choice of the chapter contributions and related authors, particular attention has been devoted to cover all the aspects of polymeric antioxidant materials.

After the first chapter which deals with a complete overview of the antioxidant compounds, the book goes in detail with the description of the natural and synthetic polymeric antioxidants, with particular attention to both their chemical and biological properties. The naturally occurring polymeric antioxidant (e.g. polyphenols and flavonoids) are subsequently treated, and the principal synthetic approach based on enzymatic catalysis for their synthesis explored. After this introductory section, polysaccha-ride biopolymers produced by different organisms are analyzed in terms of antioxidant properties and the most significant chemical approaches for their modification with the aim to improve their antioxidant activity are highlighted. The overview on natural poly-mers concludes with the treatment of particular kinds of antioxi-dant polymers (polysaccharides and proteins) from marine origin and to their extraction methodologies.

The section about synthetic antioxidant polymers starts with the description of enzyme mimics and follows with an overview on conducting polymers. Subsequently, a more chemical approach is present in the description of functionalized side-chain polymer with polyphenol moieties.

The final chapters of the book are mainly focused on applica-tions. After an overview of the possible industrial application of the antioxidants in which particular attention is devoted to the differences between the applicability of low- and high-molecular weight antioxidants, as well as to some synthetic approaches for their preparation, the book elucidates the applicability of poly-mers and antioxidants in pharmaceutical and biomédical fields for the preparation of innovative drug delivery devices and tissue scaffolds.

Finally, the editors would like to thank all the contributing authors for their high quality cooperation which is the primary intent of this edited volume.

Giuseppe Cirillo Francesca lemma

March 23,2012

List of Contributors

David Cochran is a PhD candidate under Dr. Thomas Dziubla in Chemical Engineering at the University of Kentucky, Lexington KY. He is also a participant in the Integrative Graduate Education and Research Traineeship (IGERT) program. His research is focused on the development of actively targeted antioxidant polymers for the treatment of inflammation mediated events such as metal particu-late inhalation, ischemia/reperfusion injury, and cancer metastasis.

Manuela Curcio was born in Rossano, Italy and received a degree in Chemistry and Pharmaceutical Technology cum laude from the University of Calabria in 2006. She continued her graduate stud-ies at the University of Calabria and completed her PhD in 2009. Since 2006 she has been engaged in teaching activities as a tutor, and from 2010-2011 as a contract professor. In 2011 she became CEO of Macrofarm s.r.L, a spin-off of the University of Calabria, and received a post-doctoral fellowship.

Thomas Dziubla is an Assistant Professor of Chemical Engineering at the University of Kentucky, Lexington KY. He has authored over 30 publications and 4 patents in the field of drug delivery, antioxidant therapy and biomaterials. He has recently been awarded the Kentucky Commercialization Fund Award for his work with degradable antioxidant polymers.

H. Stephen Ewart completed his PhD in Biochemistry from Memorial University of Newfoundland and post-doctoral studies at Toronto's Hospital for Sick Children and at the University of Calgary. He has focused on the discovery and commercialization of marine-based nutraceuticals and functional food ingredients at Ocean Nutrition Canada Limited and at National Research Council of Canada. Currently he is an independent research consultant.

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xx LIST OF CONTRIBUTORS

M. Carmen Gomez-Guillen is a Doctor of Veterinary Sciences at the Complutense University of Madrid and is a Senior Research Scientist.

Begona Giménez Castillo is a Doctor of Veterinary Sciences at the University of Zaragoza and is a Research Scientist.

M. Elvira Lopez-Caballero is a Doctor of Veterinary Sciences at the Complutense University of Madrid and is a Research Scientist.

M. Pilar Montero Garcia is a Doctor in Biological Sciences at the Complutense University of Madrid and is a Professor of Research.

These 4 authors are affiliated with the Spanish National Research Council (CSIC) at the Institute of Food Science, Technology and Nutrition (ICTAN) in Madrid (Spain), in the Development, Valorisation and Innovation of Fish Products Group. The main research lines are focused on the science and technology of fish products, especially on quality, minimal processing technologies, protein functionality, design and development of functional prod-ucts and valorisation of protein wastes.

Chunhuan He is originally from Guangxi Province, China. He received a BS and MS degree in Organic Chemistry from Guangxi Normal University. He began his independent research career in 2010 as an Assistant Researcher at Guangxi Institute of Chinese Medicine and Pharmaceutical Science. His research interests include the separa-tion and investigation of the biological activity of Chinese medicines.

Xiao wen Ji is originally from Guangxi Zhuang Autonomous Region, China. She received a BS and MS degree in Analytical Chemistry from Guangxi Normal University. She began her independent research career in 2010 as an Assistant Researcher at Guangxi Botanical Garden of Medicinal Plants, the Chinese Academy of Sciences. Her research interests include the investigation of the bio-logical activity of herbs and pharmaceutical analysis.

Guangling Jiao obtained a Bachelor's degree in Pharmacy from Yantai University (China). She has three years' visiting work experi-ence at the Institute for Marine Biosciences-National Research Council of Canada. Currently a PhD candidate at the Ocean University of China, her field of interest is marine polysaccharides-based drugs and functional food studies.

LIST OF CONTRIBUTORS xxi

Paul Kilmartin is an Associate Professor in the School of Chemical Sciences at the University of Auckland, New Zealand. He obtained his PhD from the same department in 1997 in the field of conducting polymer electrochemistry and has continued to undertake research in applications of conducting polymers and in the electrochemistry of beverage polyphenols.

Young-Jin Kim received his BS degree in 1996 and MS degree in 1998 from Kyungpook National University. In 2004, he received his PhD from Kyoto University He joined Nano Practical Application Center as Team Leader in 2005. He moved to the Department of Biomédical Engineering, Catholic University of Daegu as Assistant Professor in 2007. His main interests are biopolymers and biomimetic materials.

Gui-min Luo graduated from the Chemistry Department of Jilin University in 1966. He has proposed a new strategy for generating abzymes and successfully prepared the first selenium-containing abzyme in the world. He has frequently visited the University of Southern California and Columbia University for cooperative research. So far, he has published more than 98 papers collected by SCI.

Mohammad S. Mubarak received his BS and MS degrees in chemis-try from the University of Jordan in 1976 and 1978, respectively and obtained his PhD degree from Indiana University, Bloomington, USA in 1982. His research program is broadly based on synthetic organic chemistry, especially the synthesis of compounds with expected biological activity, in addition to work that involves syn-thesis and sorption properties of chelating polymers. He is the author and coauthor of more than 100 research papers.

Ashveen V. Nand obtained his BS and MS degrees in Chemistry from the University of the South Pacific, Fiji Islands. Currently, he is working on his PhD thesis at the University of Auckland under the supervision of Prof. Paul Kilmartin. He is investigating the application of intrinsically conducting polymers as antioxidant materials.

Yingming Pan is originally from Jiangxi Province, China. He received a BS degree in Organic Chemistry from Gannan Normal University, a MS degree from Guangxi University, and his PhD

xxii LIST OF CONTRIBUTORS

from Xiamen University. In 2009, he became full Professor in Organic Chemistry in Guangxi Normal University. His research interests include the separation, synthesis, and investigation of the biological activity of natural compounds.

Ashok Patel is a former Marie Curie International Incoming Fellow and is currently working as a Research Scientist (under NanoNextNL consortium) at Unilever R&D Vlaardingen, the Netherlands.

Sonia Trombino graduated in Pharmacy at the University of Calabria (Italy), where in 2003 she also specialized in Clinical Pathology. Since 2006 she has been a researcher at the Faculty of Pharmacy of the same university. Her research activity involves the synthesis of hydrogels made from natural polymers such as pro-teins and polysaccharides; the preparation and characterization of micro- and nanoparticles for drug delivery; the chemical modifica-tion of natural fibers, and; the evaluation of antioxidant activity of natural and synthetic polymers.

Hiroshi Uyama received his BS degree in 1985 and MS degree in 1987 from Kyoto University. In 1988, he joined the Department of Applied Chemistry, Tohoku University, as Assistant Professor. In 1997 he moved to the Department of Materials Chemistry, Kyoto University. In 2004, he was appointed as a full Professor at Osaka University. His main interests are biomass plastics and functional biopolymers.

Krassimir Velikov is an Expertise Team Leader /Science Leader at Unilever R&D, the Netherlands and Adjunct Assistant Professor at Debye Institute for Nanomaterials Science, Utrecht University, the Netherlands.

Jarmila Vinsovâ, Prof. RNDr. and PhD, works at the Department of Organic and Inorganic Chemistry, Faculty of Pharmacy in Hradec Krâlové, Charles University in Prague (the Czech Republic). Her research area is the design and synthesis of new compounds with antimicrobial activities, especially antimycobacterial and antifun-gal activity and prodrug modelling. She is a Vice-Chairman of The Czech Chemical Society.

Cheng Wang received his MS in Biochemistry in 2006 from the Inner Mongolia University of Science and Technology and is currently pursuing his PhD at the Key Laboratory of Molecular Enzymology

LIST OF CONTRIBUTORS xxiii

and Engineering of the Ministry of Education in Jilin University. His current research interests include selenium-containing abzyme with antioxidant activity.

Hengshan Wang was born in Beijing, China in 1965. He received a MS degree in Phytochemistry in 1990 and a PhD in Biochemistry from Lanzhou University in 2000. In 2001, he became full Professor in Organic Chemistry at Guangxi Normal University. His research interests involve the fields of bioactive natural products in regard to new synthetic methods and some aspects of medicinal chemistry.

Carl-Eric Wilén is currently Professor of Polymer Technology at Âbo Akademi University, Finland. He is also a partner of the Finnish Center of Excellence for Functional Materials (FUNMAT). His main research interests are functional polymers, plastic addi-tives and printable electronics. He has published more than 60 peer-reviewed papers and is an inventor in over 15 issued or pending patent applications.

Gang-lin Yan received his BS in Chemistry in 1977 from Jilin University. After graduation, he joined the faculty of the Key Laboratory for Molecular Enzymology and Engineering of the Ministry of Education in Jilin University. His main research inter-ests include chemical synthesis and biosynthesis of antioxidant enzyme mimics.

Guangli Yu completed his PhD in Medicinal Chemistry from Ocean University of China. His focus is the study of marine carbohydrate-based drugs and functional foods at the school of Medicine and Pharmacy, Ocean University of China. He is currently a Professor and Vice-Director of Key Laboratory of Marine Drugs, Ministry of Education of China.

Hiba Zalloum is a researcher at Hamdi Mango Center for Scientific Research at the University of Jordan and holds a Master degree in Chemistry. Her practical research dealt with the syn-thesis, chelation and sorption properties of chelating polymers. Recently, her research interest is turning to molecular modeling and the drug discovery field.

Junzeng Zhang obtained a PhD in Natural Products Chemistry from the Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, and a MBA from

xxiv LIST OF CONTRIBUTORS

Saint Mary's University. His post-doctoral research experience was at Peking University, Rutgers University and Institut Armand-Frappier (Quebec). He then joined Ocean Nutrition Canada Limited to work on the discovery and commercialization of marine-based nutraceuticals and functional food ingredients. He is currently a research officer at the Institute for Nutrisciences and Health, National Research Council of Canada.

Xiaoliang Zhao obtained a Bachelor's degree in Biotechnology from Northwest Normal University (China). He then worked at Tarim University (China) on bioactive polysaccharides research. Currently a graduate student of Ocean University of China, he is studying the structure-activities of marine poly-/oligosaccharides using glycoarray technology.

1 Antioxidants: Introduction

Chunhuan He1'2, Yingming Pan1, Xiaowen Ji1, Hengshan Wang1

1Key Laboratory for the Chemistry and Molecular Engineering of Medicinal Resources (Ministry of Education of China), School of Chemistry & Chemical

Engineering of Guangxi Normal University, Guilin, P. R. China 2Guangxi Institute of Chinese Medicine & Pharmaceutical Science, Nanning,

P R. China

Abstract It is well known that reactive oxygen species (ROS) are involved in a variety of physiological and pathological processes. ROS are continu-ously balanced by antioxidative defense systems in healthy individu-als. However, when the physiological balance between pro-oxidants and antioxidants is disrupted in favor of the former, oxidative stress occurs ensuing in potential damage for the organism. Therefore in recent years, the role and beneficial effects of antioxidants against various disorders and diseases induced by oxidative stress have received much attention. An antioxidant is a substance which when present at low concentrations compared to those of oxidizable substrates, significantly delays or inhibits oxidation of that substrate. The main content of this chapter includes the meaning of antioxidant, categories of antioxidants, antioxidant evaluation methods, and their functional mechanisms and adverse effects.

Keywords: Antioxidant, category, evaluation methods, mechanisms, adverse effect

1.1 The Meaning of Antioxidant Lipid oxidation in food and biological systems is responsible for a multitude of adverse effects and implications in the food indus-try as well as in human health. Oxidation may occur in foods during harvesting, processing, and storage. It is responsible for

Giuseppe Cirillo and Francesca lemma (eds.) Antioxidant Polymers, (1-22) © Scrivener Publishing LLC

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2 ANTIOXIDANT POLYMERS

rancid odors and flavors of foods, with a consequent decrease in nutritional quality and safety caused by the formation of second-ary, potentially toxic compounds, thus making the lipid or lipid-containing foods unsuitable for consumption [1]. It has also been reported that oxidation in vivo is associated with pathophysiology of human health problems such as carcinogenesis, inflammation, atherosclerosis, and aging [2-5]. Among the methods employed for preventing lipid oxidation, the addition of antioxidants is the most effective, convenient, and economical strategy for stabilizing food and non-food commodities [6]. The common definition of an antioxidant is any substance that significantly delays or prevents oxidation of that substrate when present at low concentrations compared with those of an oxidizable substrate [7]. In the field of foods, antioxidants are classified as compounds that are able to delay, retard or prevent autooxidation processes [8, 9]. In terms of the effects in the human body, an antioxidant is a substance in foods that significantly decreases the adverse effects of reactive species, such as reactive oxygen and nitrogen, on normal physi-ological functions, as defined by the Institute of Medicine [10]. Antioxidants such as butylated hydroxyanisole (BHA), butylated hydroxutoluene (BHT), and propyl gallate (PG) have been used by food manufacturers worldwide to retard food lipid oxidation and thus prevent quality deterioration and improve the shelf-life of products [11].

1.2 The Category of Antioxidants and Introduction of often Used Antioxidants

According to the pathways of antioxidant production, there are natural antioxidants, synthetic antioxidants and nature-identical antioxidants [12]. The most widely encountered way of antioxi-dant formation is natural antioxidant, which is synthesized by various microorganisms, fungi, and even animals, but most often by plants. Synthetic antioxidants are produced by human experts by way of synthesis or biosynthesis in the industry. And nature-identical antioxidants are found in foods, but synthesized in the industry.

Lipid oxidation is one of the major reasons for deterioration of food products during processing and storage. Its mechanism is shown in Figure 1.1 [13, 14]. A large number of synthetic and

ANTIOXIDANTS: INTRODUCTION 3

R-H ► FT+H-

R-OOH ► R-0-+-OH R* + 0 2 ► R-02

#

► R-OOH + H' 2R•R-0•R-02•

[1a] [1b] [1c] [1d]

-> Stable products [1 e]

Figure 1.1 Mechanism of lipid oxidation [13,14].

OH OH OH OH (CH3)3C^L.C(CH3)3 ,A^C(CH3)3 A ^ C ( C H 3 ) 3 H O ^ L ^ O H

CH3

BHT OCH3

3-BHA OH TBHQ

C00CH2CH2CH3

PG

COOH

Resveratrol Caffeic acid

HO

COOH

HO OH

Gallic acid

OH OH O

Quercetin OH

Catechin

OH O Luteolin

OH OH O

Kaempferol

Figure 1.2 The frequently encountered antioxidants.

OH OH Epigallocatechin

natural antioxidants have been shown to induce beneficial effects on food storage. The most frequently encountered antioxidants are listed in Figure 1.2. According to the mechanism of lipid oxi-dation, several types of inhibitors of lipid oxidation are available:

4 ANTIOXIDANT POLYMERS

inhibitors of free-radical oxidation reactions (also called preven-tive antioxidants), inhibitors interrupting the propagation of the autoxidation chain reaction (called chain-breaking antioxidants), singlet oxygen quenchers, synergists of proper antioxidants, reducing agents, metal chelators, and inhibitors of pro-oxidative enzymes [12].

There is a growing interest in natural antioxidants found in plants from a safety point of view. Polyphenols comprise a large class of antioxidants and include flavonoids, anthocyanins, phenolic acids, lignans, and stilbenes. They have been receiving increasing inter-est from consumers and manufacturers in the past few decades because of numerous health benefits such as their antibacterial, anti-inflammatory, antiallergic, hepatoprotective, antithrombotic, antiviral, anticarcinogenic, and vasodilatory actions [15, 16]. We will present a brief introduction of some frequently encountered phenolic antioxidants including synthetic antioxidants and natural antioxidants in the following part.

1.2.1 BHT

Butylated hydroxy toluene (BHT), namely 2,6-bis(l,l-dimethylethyl)-4-methylphenol or 3,5-di-tert-butylhydroxy-toluene, is a synthetic, highly lipid-soluble antioxidant, which is commonly used in the manufacture of plastics, elastomers, oils, lubricants, vitamins and fragrances, as well as in the field of preservation of human foods, cosmetics and other lipid-con-taining products [17-19]. BHT is allocated an acceptable daily intake (ADI) of 0-0.3 m g / k g body weight. It is able to terminate lipid peroxidation chain reactions before the spoilage of food by donating hydrogen-atoms of phenol hydroxyl groups and sta-bilizing the peroxyl radicals [20]. It was reported that adminis-tration of BHT to animals can not only prevent sugar-induced cataract and inhibit cholesterol-induced atherosclerosis, but also diminished tumor development in rats exposed to cancerogenic compounds [18]. Considering the increased usage of BHT in our foods, concern over the safety of BHT has been growing and its biological activities have been investigated in the past few decades. BHT exacerbates a chronic urticaria in an early clinical study [21]. Lung inflammation is induced in mice by BHT admin-istration and hepatic toxicity in rats has been found when admin-istered orally [22-24]. Moreover, BHT acts as a tumor promoter