Polysaccharides E-Book
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- Herausgeber: John Wiley & Sons
- Kategorie: Fachliteratur
- Sprache: Englisch
This book provides the whole spectrum of polysaccharides from basic concepts to commercial market applications. Chapters cover various types of sources, classification, properties, characterization, processing, rheology and fabrication of polysaccharide-based materials and their composites and gels. The applications of polysaccharides include in cosmetics, food science, drug delivery, biomedicine, biofuel production, marine, packaging, chromatography and environmental remediation. It also reviews the fabrication of inorganic and carbon nanomaterials from polysaccharides. The book incorporates industrial applications and will fill the gap between the exploration works in the laboratory and viable applications in related ventures.
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Veröffentlichungsjahr: 2021
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Table of Contents
Cover
Title Page
Copyright
Preface
1 Natural Polysaccharides From Aloe vera L. Gel (Aloe barbadensis Miller): Processing Techniques and Analytical Methods
1.1 Introduction
1.2 Applications of A. vera Mucilaginous Gel or Fractions
1.3 Aloe vera Gel Processing
1.4 Analytical Methods Applied
1.5 Conclusion
References
2 Cell Wall Polysaccharides
2.1 Introduction to Cell Wall
2.2 Plant Cell Wall Polysaccharides
2.3 Algal Cell Wall Polysaccharides
2.4 Fungal Cell Wall Polysaccharides
2.5 Bacterial Cell Wall Polysaccharides
References
3 Marine Polysaccharides: Properties and Applications
3.1 Introduction
3.2 Polysaccharide Origins
3.3 Properties
3.4 Applications of Polysaccharides
3.5 Conclusions
References
4 Seaweed Polysaccharides: Structure, Extraction and Applications
4.1 Introduction
4.2 Conclusion
References
5 Agars: Properties and Applications
5.1 History and Origin of Agar
5.2 Physical Properties of Agar Producing Seaweeds
5.3 Agar Manufacturing
5.4 Structure of Agar
5.5 Heterogeneity of Agar
5.6 Physico-Chemical Characteristics of Agar
5.7 Chemical Characteristics of Agar
5.8 Factors Influencing the Characteristics of Agar
5.9 Uses of Agar in Various Sectors
5.10 Conclusion and Discussion
References
6 Biopolysaccharides: Properties and Applications
6.1 Structure and Classification of Biopolysaccharides
6.2 Uses and Applications of Biopolysaccharides
6.3 Conclusion
References
7 Chitosan Derivatives: Properties and Applications
7.1 Introduction
7.2 Properties of Chitosan Derivatives
7.3 Applications of Chitosan Derivatives
7.4 Conclusions
Acknowledgement
References
8 Green Seaweed Polysaccharides Inventory of Nador Lagoon in North East Morocco
8.1 Introduction
8.2 Nador Lagoon: Situation and Characteristics
8.3 Seaweed
8.4 Polysaccharides in Seaweed
8.5 Algae Polysaccharides in Nador Lagoon’s Seaweed
8.6 Conclusion
References
9 Salep Glucomannan: Properties and Applications
9.1 Introduction
9.2 Production
9.3 Composition and Physicochemical Structure
9.4 Rheological Properties
9.5 Purification and Deacetylation
9.6 Food Applications
9.7 Health Benefits
9.8 Conclusions and Future Trends
References
10 Exudate Tree Gums: Properties and Applications
10.1 Introduction
10.2 Nanobiotechnology Applications
10.3 Minor Tree Gums
10.4 Conclusions
Acknowledgment
References
11 Cellulose and its Derivatives: Properties and Applications
11.1 Introduction
11.2 Main Raw Materials
11.3 Composition and Chemical Structure of Lignocellulosic Materials
11.4 Cellulose: Chemical Backbone and Crystalline Formats
11.5 Cellulose Extraction
11.6 Cellulose Products and its Derivatives
11.7 Main Applications
11.8 Conclusion
References
12 Starch and its Derivatives: Properties and Applications
12.1 Introduction
12.2 Physicochemical and Functional Properties of Starch
12.3 Modification of Starch
12.4 Application of Starch and its Derivatives
12.5 Conclusion
References
13 Crystallization of Polysaccharides
13.1 Introduction
13.2 Principles of Crystallization of Polysaccharides
13.3 Techniques for Crystallinity Measurement
13.4 Crystallization Behavior of Polysaccharides
13.5 Polymer/Polysaccharide Crystalline Nanocomposites
13.6 Conclusion
References
14 Polysaccharides as Novel Materials for Tissue Engineering Applications
14.1 Introduction
14.2 Types of Scaffolds for Tissue Engineering
14.3 Biomaterials for Tissue Engineering
14.4 Polysaccharide-Based Scaffolds for Tissue Engineering
14.5 Current Challenges and Future Perspectives
Acknowledgements
References
15 Structure and Solubility of Polysaccharides
15.1 Introduction
15.2 Polysaccharide Structure and Solubility in Water
15.3 Solubility and Molecular Weight
15.4 Solubility and Branching
15.5 Polysaccharide Solutions
15.6 Conclusions
Acknowledgments
References
16 Polysaccharides: An Efficient Tool for Fabrication of Carbon Nanomaterials
16.1 Introduction
16.2 Aerogels
16.3 Graphene-Like Materials and Nanotubes Produced From Polysaccharides
16.4 Biocarbon Quantum Dots
16.5 Membranes Containing Carbon Nanoparticles Derived From Cellulose
16.6 Conclusions
References
17 Rheology and Structural Properties of Polysaccharides
17.1 Introduction
17.2 General Structural Features of Polysaccharides
17.3 Main Types of Polysaccharides and Their Structural Properties
17.4 Rheological Behavior of Polysaccharides
17.5 Conclusions
References
18 Gums-Based Bionanostructures for Medical Applications
18.1 Plants and Their Bioactive Compounds
18.2 Natural Gums—Physicochemical Features
18.3 Sources of Natural Gums
18.4 Classification of Gums
18.5 Composition of Natural Gums
18.6 Extraction and Purification of Natural Gums
18.7 Modification and Hydrolysis of Natural Gums
18.8 Medical Applications of Gums-Based Bio-Nanostructures
18.9 Conclusions
References
19 Alginates: Properties and Applications
19.1 Introduction
19.2 Properties of Sodium Alginate (Na-Alg)
19.3 Chemical Properties
19.4 Applications
19.5 Conclusions and Prospects
Acknowledgments
Abbreviations
References
20 Marine Polysaccharides: Properties and Applications
20.1 Introduction
20.2 Marine Bacteria That Produce Polysaccharides
20.3 Marine Fungi That Produce Polysaccharide
20.4 Production, Extraction and Purification of Polysaccharides
20.5 Characterization via Molecular, Biochemical and Cultural Characterization of Marine Polysaccharides
20.6 Conclusion and Future Recommendation to Knowledge
References
21 Polysaccharides: Promising Constituent for the Preparation of Nanomaterials
21.1 Introduction
21.2 Preparation of Polysaccharide-Dependent Nanomaterials
21.3 Biocompatibility of Carbon-Based Nanomaterials
21.4 Conclusions and Summary
References
22 Anticancer Potential of Polysaccharides
22.1 Introduction
22.2 Mode of Action
22.3 Polysaccharides in Cancer Treatment
22.4 Polysaccharides in Conventional Therapies
22.5 Concluding Remarks and Future Trends
References
23 Polysaccharide-Based Membrane for Packaging Applications
23.1 Introduction
23.2 Polysaccharides as Biomaterials for Biodegradable Packaging
23.3 Properties of Polysaccharide-Based Packaging Film or Coating
23.4 Polysaccharides-Based Nanocomposites Packaging
23.5 Polysaccharides-Based Films and Coatings in Food Packaging Applications
23.6 Conclusion and Prospects
References
24 Applications of Polysaccharides in Cancer Treatment
24.1 Introduction
24.2 Types of Polysaccharides Used in Cancer Treatment
24.3 Mechanism of Polysaccharides as Anticancer Agent
24.4 Usage of Polysaccharides in Preclinical and Clinical Models of Cancer
24.5 Conclusion and Future Perspectives
References
25 Application of Chitosan-Based Catalysts for Heterocycles Synthesis and Other Reactions
25.1 Introduction
25.2 Recent Research Reports
25.3 Conclusion
References
26 Preparation and Applications of Polysaccharide-Based Composites
26.1 Introduction
26.2 Types
26.3 Importance
26.4 Fabrication and Applications of Polysaccharide-Inorganic-Based Composites
26.5 Recent Applications
26.6 Conclusion
References
27 Polysaccharide-Based Liquid Crystals
27.1 Introduction
27.2 Polysaccharides-Based Liquid Crystals
27.3 Conclusion
References
28 Patents on Polysaccharide Applications
28.1 Introduction
28.2 Polysaccharides in Medical Application
28.3 Polysaccharides in Cosmetic Application
28.4 Polysaccharides in Battery Components
28.5 Polysaccharides in Paper Manufacture
28.6 Conclusion
References
29 Applications of Polysaccharides in Controlled Release Drug Delivery System
29.1 Introduction
29.2 Polysaccharides From Plant Sources and Their Derivatives
29.3 Gums
29.4 Polysaccharides From Algal Sources
29.5 Polysaccharides From Fungal Sources
29.6 Polysaccharides From Animals Sources and Their Derivatives
29.7 Polysaccharides From Microorganisms
References
30 Applications of Polysaccharides in Nutrition and Medicine
30.1 Introduction
30.2 Sources of Polysaccharides
30.3 Role of Polysaccharides in Nutrition
30.4 Biomedical Applications of Polysaccharides
30.5 Conclusion
References
31 Synthetic Polysaccharide-Based Vaccines: Progress and Achievements
31.1 A Brief History of Vaccination
31.2 The Leverage of Synthetic Polysaccharide-Based Vaccines Over Natural Polysaccharide-Based Vaccines
31.3 The Principles of Synthetic Polysaccharide-Based Vaccines
31.4 The Opportunities and Prospects of Synthetic Polysaccharide-Based Vaccine Technologies
References
32 Polysaccharides Derived From Natural Sources: A Panacea to Health and Nutritional Challenges
32.1 Introduction
32.2 Different Types of Polysaccharides Derived From Different Natural Sources
32.3 Production, Extraction and Purification of Polysaccharides
32.4 Specific Examples of Polysaccharides and Their Various Applications in Nutrition and Medicine
32.5 Conclusion and Recommendation to Knowledge
References
Index
End User License Agreement
List of Tables
Chapter 1
Table 1.1 Process for obtaining mucilaginous gel, polysaccharide fraction, oligo...
Table 1.2 Methods of chemical characterization of mucilaginous gel and its deriv...
Chapter 3
Table 3.1 Types, sources, monomers, and linkages found in common polysaccharides...
Chapter 4
Table 4.1 Composition of fucoidans from different seaweed species.
Chapter 5
Table 5.1 Classification of the taxa of agarophytes [9].
Table 5.2 Types of different agars, their applications and their respective agar...
Table 5.3 Region-wise global agar applications [31].
Table 5.4 Different types of agar medium with respective uses and description.
Chapter 7
Table 7.1 Structures of selected chitosan derivatives.
Table 7.2 Applications of carboxymethyl chitosan derivatives in bone marrow appl...
Table 7.3 Antimicrobial applications of auaternized ammonium chitosan.
Table 7.4 Chitosan based derivatives for encapsulation of nutrients.
Chapter 8
Table 8.1 The global estimate of the three polysaccharides (Agar, Alginates, Car...
Chapter 9
Table 9.1 Rheological results of the food systems containing salep.
Table 9.2 The methods to separate polysaccharides or increase/isolate glucomanna...
Chapter 10
Table 10.1 The specifications for various food grade exudate tree gums as per Bu...
Table 10.2 The other minor exudate gums produced by trees belonging to different...
Chapter 11
Table 11.1 Natural resources from different origins and the content, in wt%, of ...
Table 11.2 Cellulose and cellulose derivatives used in building products.
Chapter 12
Table 12.1 Botanical sources of starch and their corresponding amylose/amylopect...
Chapter 13
Table 13.1 Different features of important members of polysaccharide family [8].
Table 13.2 Cl of celluloses determined by four different methods by the authors.
Table 13.3 Unit cell symmetry and dimension of cellulose polvmorphs.
Chapter 14
Table 14.1 The different types of biomaterials/polymers employed in tissue engin...
Chapter 15
Table 15.1 Various polysaccharides and their solubility in water.
Chapter 16
Table 16.1 The content, mass %, of components in plant cellulose and its crystal...
Table 16.2 Residual content of BCC impurities (%) after each purification stage ...
Table 16.3 Specific capacitance of different types of carbon-based electrodes (b...
Chapter 19
Table 19.1 Various types of alginate-based film for wound dressing materials.
Table 19.2 Various types of alginate-based hydrogels and fibres for wound dressi...
Table 19.3 Alginate-based adsorbents for ion removal from water.
Chapter 20
Table 20.1 Typical examples of marine microorganisms that produce polysaccharide...
Chapter 22
Table 22.1 Different types of cancers and polysaccharides studies for their anti...
Chapter 23
Table 23.1 Characteristics of polysaccharide-based materials extracted from plan...
Table 23.2 Characteristics of polysaccharide-based materials synthesized by micr...
Chapter 26
Table 26.1 Examples of polysaccharides [4].
Table 26.2 Functions of different polysaccharides.
Table 26.3 Synthesis approaches and properties of different inorganic fillers [2...
Chapter 28
Table 28.1 Example of polysaccharides derivatives.
Table 28.2 List of patents for drug delivery, wound dressing and tissue engineer...
Table 28.3 List of patents for cosmetic application.
Chapter 32
Table 32.1 Polysaccharides from different natural sources.
Table 32.2 The naturally occurring herbal polysaccharides.
Table 32.3 Animal derived polysaccharides.
Table 32.4 Microbial derived polysaccharides.
Table 32.5 List of several homoglycans from different sources.
Table 32.6 Glycosaminoglycans (GAGs) and other heteroglycans.
Table 32.7 List of mucopolysaccharidoses.
Guide
Cover
Table of Contents
Title Page
Copyright
Preface
Begin Reading
Index
End User License Agreement
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Scrivener Publishing100 Cummings Center, Suite 541JBeverly, MA 01915-6106
Publishers at ScrivenerMartin Scrivener ([email protected])Phillip Carmical ([email protected])
Polysaccharides
Properties and Applications
Edited by
Inamuddin, Mohd Imran Ahamed
Rajender Boddula
and
Tariq Altalhi
This edition first published 2021 by John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA and Scrivener Publishing LLC, 100 Cummings Center, Suite 541J, Beverly, MA 01915, USA © 2021 Scrivener Publishing LLC For more information about Scrivener publications please visit www.scrivenerpublishing.com.
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Library of Congress Cataloging-in-Publication Data
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Preface
Polysaccharides are versatile and abundant biopolymers derived from natural resources which have emerged as a sustainable and eco-friendly alternative to conventional polymers or traditional plastics. Due to their unique properties, such as good stability, safety, low tox-icity, low cost, hydrophilicity, supramolecular structure, gelation ability, biodegradability and flexibility, polysaccharides have been the subject of multidisciplinary research in the fields of chemistry, physics, food science, materials science and biology. This book presents the entire spectrum of polysaccharide-related topics—from basic concepts to commercial market applications. The chapters cover various sources, classifications, properties, charac-terizations, processing methods, rheologies and fabrications of polysaccharide-based mate-rials and their composites and gels. Also covered are the applications of polysaccharides in cosmetics, food science, drug delivery, biomedicine, biofuel production, the applications, packaging, chromatography and environmental remediation. In addition to incorporating industrial applications and filling in the gap between exploratory works in the laboratory and viable applications in related ventures, this book also reviews the fabrication of inor-ganic and carbon nanomaterials from polysaccharides.
Since recent developments in the field are highlighted and real examples of polysaccha-rides in practice are provided along with key references, this book is an invaluable resource for both industry professionals and entrepreneurs in the field. As can be seen from the range of topics covered in the chapters summarized below, the book is also essential read-ing for industrialists, scientists, university professors, lecturers, researchers, doctoral and master students working in the fields of polymer science and technology, material science, chemistry, biology, and medicine.
Chapter 1 describes the composition of aloe vera mucilaginous gel, its major polysac-charides and their applications. The processes for obtaining the mucilaginous gel and its polysaccharide fractions, as well as the analytical methods applied for the quantification of total carbohydrates, oligosaccharides, acemannan, and free sugars are addressed.
Chapter 2 provides details about the cell wall of plant, algae, fungi and bacteria as the best reservoir of polysaccharides. Different types of polysaccharides like cellulose, hemi-cellulose and pectin representing the most prominent component of the cell wall are dis-cussed. Furthermore, various applications of polysaccharides in living organisms ranging from their structure to biological signaling are described. Additionally, various commercial applications of polysaccharides in pharmaceutical, paper, cosmetic and food industries are highlighted.
Chapter 3 primarily concentrates on the major marine polysaccharides, which in light of their diversity and complexity are addressed along with their underlying fundamental principles.
Chapter 4 provides details on the seaweed polysaccharides—agar, alginate, carrageenan, fucoidan, laminarin and ulvan—which have profound applications in food, pharmaceutical and many other chemical fields. Chemical structures and properties of polysaccharides are also discussed. Additionally, procedures for seaweed polysaccharides’ extraction and appli-cation areas are presented in detail.
Chapter 5 deals with all aspects of polysaccharide. It also discusses variable methods to alter agar characteristics according to the type of work, the heterogeneity, synergies, physico-chemical and chemical properties along with mass spectroscopic, NMR, and XRD analyses.
Chapter 6 addresses the major properties and classifications of natural polysaccharides and deals with the applications of these green and sustainable resources in many different fields and industries, including biomedicine, food, cosmetics, textiles, wastewater treat-ment, and energy production.
Chapter 7 discusses the properties of chitosan enhanced by the addition of various functional groups. The understanding of chitosan derivatives for various biomedical, envi-ronmental, and food applications which can help in the development of other novel appli-cations are also discussed.
Chapter 8 discusses six different types of green seaweed containing a large amount of high-value polysaccharides (sulfated galactans, ulvan, sulfated arabinans, sulfated arab-inogalactans and mannans) in their biomass composition. Additionally, these extracted natural carbohydrates have important physiological and biological roles such as having anti-inflammatory, immunomodulation, antioxidant, anticoagulant, and anti-tumor effects in the human body.
Chapter 9 reveals the specific functional properties and nutritional value in the food applications of salep powder produced from tubers of the Orchidaceae family, an important glucomannan source. The production, cultivation, purification, deacetylation and depo-lymerization of glucomannan show new functional properties, which are summarized in detail.
Chapter 10 provides concise information on the properties and applications of exudate gums in different fields and industries, such as food, pharmaceutical, textile, paper, paint, cosmetic, nanobiotechnology, and non-food, due to their renewability, low cost, nontoxic-ity, biocompatibility and biodegradability. Also, minor tree gums and their applications are briefly covered.
Chapter 11 deals with cellulose types and configurations. Plant- and animal-based sources are listed and explained. Also, mechanical and chemical methods for plant decon-struction are discussed. Moreover, different cellulosic derivatives are discussed in detail, encompassing their properties and applications.
Chapter 12 provides a detailed discussion on starch structure, its physicochemical prop-erties and application of starch and its derivatives. Also, methods of starch modification are briefly discussed.
Chapter 13 discusses the crystallization behavior of polysaccharides and techniques used in the determination of their crystallization. Applications of crystalline polysaccharides for packaging and biomedical needs are specifically outlined.
Chapter 14 describes the significance of polysaccharides employed for tissue engi-neering applications. The principles involved, the biomaterials used, and different scaf-fold fabrication techniques employed are discussed. Emphasis is given to the applications of different polysaccharide-based scaffolds. The necessity to improve the efficiency of polysaccharide-based scaffolds is described.
Chapter 15 discusses the structure of polysaccharides and how structural integration plays a pivotal role in governing the polysaccharide dissolution in water. Polysaccharide solubility is explained based on various factors such as intermolecular forces, molecular weight, branching, and chemical modification of biopolymer.
Chapter 16 is devoted to nanomaterials, such as aerogels, graphene sponge, quantum dots and nanotubes, produced from natural polysaccharides: plant and bacterial cellulose, chitosan, and alginate. The effect of carbonization conditions on the morphology and func-tional properties of biocarbon is considered with a focus on the practical application of the nanomaterials.
Chapter 17 presents the main structural properties of the most relevant types of poly-saccharides. Significant investigations on the rheological behavior of polysaccharides and complex systems derived from them are discussed in regards to the polymer chemical structure, including the applicability of such materials.
Chapter 18 elaborates the use of novel gum-based nanocomposites with particular emphasis on their biomedical applications. In contrast to their synthetic counterparts, the naturally occurring gum polysaccharides and their derived nanostructured materials exhibit a range of applications in the biomedical sector owing to their exceptional struc-tures, physicochemical properties, and functionalities.
Chapter 19 discusses the crucial physical and chemical properties of alginate. It also summarizes the important applications of alginate in biomedical fields such as bone tissue engineering, and in pharmaceutical applications such as wound dressing, protein delivery, and delivery of vaccines.
Chapter 20 provides detailed information about the biological function, modes of action, and the application of marine-derived functional polysaccharide as a sustainable solution that could mitigate several challenges affecting mankind.
Chapter 21 discusses various polysaccharide-based nanostructured materials and nanoparticles and their importance in food industries. It also includes fabrication of nano- and microparticles using various methods such as electrospinning, dip coating, film cast-ing, and physical mixing, layer-by-layer assembly, colloidal assembly and co-precipitation, in-situ nanoparticles preparation and ionotropic gelation. The biocompatibility of carbon-based nanomaterials is also discussed.
Chapter 22 describes the anticancer potential of polysaccharides and their utilization in anticancer therapy. Several modes of action of polysaccharides to treat cancer are elab-orated. Also discussed are the applications of anticancer polysaccharides in different types of cancers and the anticancer effects of polysaccharides in traditional therapies such as chemotherapy.
Chapter 23 discusses the various sources of polysaccharides-based biomaterials and their properties that are beneficial for the development of membranes. The application of polysaccharides membranes in food packaging is also discussed in detail. The advantage of using nano-based polysaccharides materials in improving the physical and mechanical properties of membranes are also explained.
Chapter 24 details different sources of natural polysaccharides with potent anticancer activity. It also explains the mechanism of action, cell signaling and immunomodulatory effects of natural polysaccharides. Additionally, it covers information regarding the preclin-ical and clinical applications of polysaccharides in cancer treatment.
Chapter 25 showcases some of the recent research findings where chitosan, a natural bio-polymer and its derived materials, are applied as catalysts in various synthetic approaches towards various heterocyclic scaffolds.
Chapter 26 elaborates on the different types of polysaccharides derived from plants, ani-mals, and bacteria. Various polysaccharide-based composites using organic or inorganic fillers are discussed. The fabrication protocols, the interaction of the fillers with the matrix, and the properties are highlighted. Finally, the applications in diverse industrial sectors are presented.
Chapter 27 focuses on the preparation, structure, and properties of different types of liq-uid crystals from polysaccharidal materials such as cellulose, cellulose derivatives, amylose, dextrin, chitin, and schizophyllan. The effect of the addition of different substances on the thermal and photonic properties of liquid crystals is also covered.
Chapter 28 highlights international patents on the utilization of polysaccharides either in their pristine form or in their derivatives in the pharmaceutical, cosmetic, battery, and paper industries. This chapter also discusses the practical exploration of new poly-saccharide derivatives and demonstrates the need for developing technologies involving polysaccharides.
Chapter 29 discusses the use of different polysaccharides in controlled release drug deliv-ery system. These polysaccharides obtained from different plant, animal, microorganism, fungal and algal sources and their application in the development of modified release oral, transdermal, buccal and ocular drug delivery system are extensively discussed.
Chapter 30 discusses the different types and sources of polysaccharides—from micro-organisms to plants and animals—and also explains their important role in human health and nutrition. Additionally, the major health benefits of polysaccharides showing antiviral, antimicrobial, anti-inflammatory, anticancer, anti-obesity, antioxidant, and neuroprotec-tive effects, and their role in wound healing and wound dressing are discussed.
Chapter 31 presents the fundamentals of semi-synthetic and fully synthetic polysac-charide vaccine platforms and their advantages over common polysaccharide vaccines. Following a brief presentation of important historical achievements in vaccinology, the current synthetic polysaccharide vaccine pipelines, novel preclinical and clinical trials, and forthcoming opportunities in the field are also reflected.
Chapter 32 provides detailed information on the application of polysaccharides in the area of biomedicine and nutrition. The various types and modes of action of polysaccha-rides derived from numerous sources as well as their function are highlighted.
The Editors March 2021
1Natural Polysaccharides From Aloe vera L. Gel (Aloe barbadensis Miller): Processing Techniques and Analytical Methods
Silvana Teresa Lacerda Jales1,2, Raquel de Melo Barbosa3,4*, Girliane Regina da Silva5, Patricia Severino6,7 and Tulio Flávio Accioly de Lima Moura1,4
1Program on Development and Technological Innovation in Medications, Federal University of Rio Grande do Norte, Natal, Brazil
2Department of Pharmaceutical Sciences, Federal University of Paraíba, João Pessoa, Brazil
3Visiting scholar at MIT Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, USA
4Laboratory of Drug Development, Department of Pharmacy, Federal University of Rio Grande do Norte, Natal, Brazil
5Department of Chemistry, Federal Rural University of Pernambuco, Recife, Brazil
6University of Tiradentes (Unit), Aracaju, Brazil
7Institute of Technology and Research (ITP), Nanomedicine and Nanotechnology Laboratory (LNMed), Aracaju, Brazil
Abstract
Aloe vera L. (Aloe barbadensis Miller) from Asphodelaceae (Liliaceae) family, is a medicinal plant frequently used in medicines, cosmetics, and food products. Seventy-five potentially active compounds have already been identified from A. vera extract, among them: enzymes, minerals, lignin, saponins, salicylic acids, amino acids, sugars, and vitamins. In this chapter, the authors highlight the mucopolysaccharide acemannan (an acetylated glucomannan), extracted from the mucilaginous gel leaves. Acemannan has a backbone of β(1–4)-linked mannose units, partially acetylated, interspersed by glucose units, and some galactose side-chains. However, several of its structural characteristics, such as degree of acetylation, presence of glucose monomers, and its molecular weight, are always quantified because they present inconsistencies and disparities. Growing conditions of the plant and harvesting period, different processes for obtaining the gel, and its derivatives, besides the many different analytical methods applied, contribute to the lack of standardization of A. vera gel and its derivatives. Therefore, this chapter aimed to present the different techniques used for processing mucilaginous gel along with the various analytic methods applied in recent years.
Keywords: Acemannan, acetylated glucomannan, Aloe vera, polysaccharides, polymer
1.1 Introduction
Aloe vera L. (Aloe barbadensis Miller) is a medicinal plant belonging to the Liliaceae family, currently defined as Asphodelaceae by the Angiosperm Phylogeny Group III System—APG III of 2009 [1]. Of the over 300 species of Aloe, A. vera is the most widely used in medicines, cosmetics and food products. Numerous therapeutic activities, including antiviral, antibacterial, radiation protection, antioxidant, anti-inflammatory, anticancer, antidiabetic, antiallergic, immunostimulant, and ultraviolet (UV) protection have been attributed to the plant, particularly to its polysaccharides [1–7].
The leaves of A. vera can be divided into two main fractions, a thick epidermis, or outer green rind, including the vascular bundles, and an inner colorless pulp called A. vera gel. The bitter yellow exudate from the cells surrounding the vascular bundles is rich in derivatives of 1,8-dihydroxyanthraquinone and its glycosides, whereas the pulp contains proteins, lipids, amino acids, vitamins, enzymes, inorganic compounds, small organic compounds, besides different carbohydrates (soluble sugar and polysaccharides) [6].
The inner most part of the leaves (leaf pulp) of A. vera contains parenchymatous cells which produce a mucilaginous liquid referred to as A. vera pulp, among other terms such as inner gel, leaf parenchyma, mucilaginous gel and/or simply A. vera gel [4]. Water is the main constituent, ranging from 98.5 to 99.5% in the fresh plant, while around 60% of the remaining solid material is made up of polysaccharides [8, 9].
Several reports have identified acemannan as the major polysaccharide in the mucilaginous gel of A. vera. It is composed of large quantities (>60%) of partially acetylated mannose units, followed by glucose (approximately 20%) and, in lower amounts, galactose (<10%) [3, 9–11]. The acetyl groups are the only ones that are not functional groups present in sugars and appear to play a fundamental role not only in terms of physicochemical properties but also in the biological activity of A. vera [12–14].
Acemannan is highly unstable and readily degraded by different physicochemical factors including high temperatures, pH changes, microbiological factors like bacterial contamination, or by enzymatic action, such as from the mannases present in the gel [15, 16]. Studies have shown that the effects of deacetylation, i.e., removal of the acetyl group, reduce the bioactivity of the polysaccharides. Thus, the acetyl group may have functional control of acemannan affecting, at least in part, its physical properties and biological activity [14].
Controlling the chemical, functional, and physical properties of A. vera during its processing remains a significant challenge. This is due to the microbial, mechanical, enzymatic, and structural changes which take place under different climatic and processing conditions [9, 17, 18]. Thus, the choice of method for obtaining the gel is an essential factor, given that A. vera gel is often sold in concentrated powder forms [19].
Given the high activity of water in A. vera gel and its major carbohydrate composition, its shelf life is only 3–4 days at room temperature, requiring the use of stabilization processes to preserve most of the active ingredients and extend its usable life. Thus, stabilization is done to reduce the amount of water in the gel by concentrating and/or drying it, where freeze drying is the most used process [13, 20–28].
However, the conditions applied during the drying process can irreversibly modify A. vera polysaccharides, particularly acemannan, affecting its chemical structure and promoting changes in physiochemical, physiological and pharmacological properties attributed to the plant [20, 29]. A number of studies report that the drying process promotes deacetylation of the acemannan polymer [28, 30, 31], leading to a considerable reduction in its biological effect [14].
A. vera gel obtained from poor quality raw materials using non-standardized processing techniques are used to make commercial A. vera products [24, 25]. This situation creates a need for establishing standardized and validated analytical methods to guarantee the quality of products containing A. vera gel.
Bozzi et al. [19] emphasized that contamination represents a significant concern for the A. vera market, where historically, the most commonly used substance to adulterate A. vera gel is maltodextrin. Consequently, many methods have been developed for detecting contamination and establish the authenticity of A. vera gel powders, including the analyses of carbohydrates. However, in this case, the only adulteration with sugars (glucose, saccharose) or polysaccharides (i.e., maltodextrin) can be revealed [32].
Numerous different analytical methods for characterizing and quantifying A. vera gel components, such as acemannan, have been reported. Techniques used include high-performance liquid or size-exclusion chromatography, spectroscopic techniques, or colorimetric assays. However, some studies have used a more comprehensive analytical approach involving several methods concomitantly to create a profile of the material to overcome some difficulties and establish specifications.
1.1.1 Gel Composition from A. vera
Knowledge on the characteristics of A. vera allows a better understanding of the biochemical changes which take place during plant cultivation, processing and storage of its products. The gel consists predominantly of water (>98%) and polysaccharides, such as glucomannan, acemannan (acetylated glucomannan), mannose derivatives, pectins, cellulose, hemicellulose, of which acemannan is considered the main component [19]. Of the soluble sugars present in the gel, glucose accounts for over 95% [9].
According to Ni et al. [4], the sugar composition profile of the cell wall fibers, the micro-particles (degenerated organelles) and liquid gel was distinct. The mucilaginous gel, or simply gel, cannot be considered a homogenous entity, because it has three different structural components each with different chemical compositions. Galacturonic acid has been detected in the cell wall, suggesting the presence of high levels of pectin and pectic substances, the microparticles contained galactose-rich polysaccharide, and liquid gel containing mannose.
Two main types of polysaccharides present in A. vera gel are mannan-rich polysaccharides and pectic substances [33], where mannan polymer is the most studied polysaccharide from the pulp. And the liquid gel was considered the structural component owing to its viscosity and greater amount in terms of weight and volume, besides its contribution to the succulent nature of the plant. The mannan present in the gel is a soluble polysaccharide which confers the gel its viscoelastic characteristics [4].
The presence of mannose in the purified acemannan from fresh A. vera fillets ranged from 78.3 to 81.9% of the total monosaccharides, similar to data found by Chang et al. [34]. Glucose and galactose accounted for 10.1–11.7% and 4.8–6.8%, respectively (7).
However, Bozzi et al. [19] found that the fresh A. vera gel contained mainly fructose and glucose as free sugars (5.3 and 11.9 g/100 g of dry material, respectively) at a fructose:glucose ratio of 1:2. The gel also contained small amounts of free mannose, most likely from the degradation of the polysaccharide acemannan.
Chang et al. [34] conducted analyses of the amount of carbohydrate in the fractions of the skin, flowers and gel of A. vera, concluding that these fractions differ significantly, where gel contained 58.3% carbohydrate, the skin extract 37.3% and the extract from the flowers 23.4%. In 2013, Campestrini et al. [13] determined the composition of sugar in the crude extract of the pulp, where the glucose corresponded to 60.7% and mannose 28.7% as the main neutral monosaccharides, whereas for the polysaccharide fraction, glucose content was 3.9% and mannose 94.2%. The percentage of total uronic acid was 4.5 and 1.5% for the crude extract of pulp and polysaccharide fraction, respectively.
Chokboribal et al. [14] reported that the polysaccharide extracted was composed predominantly of mannose (57%), glucose (22%) and galactose (17%). Acemannan isolated from A. vera consists of a chain of tetrasaccharide of repeated units: O-(acetyl-D-mannose)O-(acetyl-D-mannose)-O-(D-glucose)-O-(acetyl-D-mannose) with a simple chain galactose at C6 of the second acetylated mannose residue [11].
Acemannan is a polysaccharide composed of β(1–4)-linked mannose residues, with acetylated C2, C3 and some galactose side-chains at C6, a feature leading to the acemannan denomination [9, 35]. On average, each mannose has one acetyl group in one of the three remaining ring positions (Figure 1.1) [10, 36].
Kiran & Rao in 2016 [37] found a higher amount of carbohydrates (72% wt/v) than polysaccharide (62% wt/v) in the fibrous fraction of mucilage, and confirmed that the major constituent in the composition of A. vera powders was polysaccharide. In their studies, Flores-López et al. [26] reported that the sum of carbohydrates and lignin found in the gel, liquid fraction and bagasse, corresponded to 57.45, 40.09 and 56.86% of the total of components present in A. vera. The authors also reported that, in all the fractions analyzed, glucose and mannose were found to be the major constituents at a ratio of 1:1. These sugars have been reported at various proportions as components of the polysaccharides of A. vera gel. They also reported the presence of a high amount of uronic acid and low amounts of galactose, confirming the occurrence of pectin polysaccharides in the gel and bagasse. Ray and collaborators [24, 25] reported that the concentration of polysaccharides varied with plant age and that plants cultivated for three years contained the highest concentration of polysaccharides, followed by the 4-year-old crop. Content also varied with time of harvest, with lower carbohydrate content during the rainy seasons.
According reported, the fluctuations in polysaccharide composition are most likely explained by seasonal influences on crop growth and by different levels of irrigation, given that the mannosyl residues are derived from the parenchyma store [9]. Thus, knowledge on how functional and bioactive properties vary with growth stage, including seasonal variation and age of plant, is of paramount importance [24, 25].
Figure 1.1 Chemical structure of mucopolysaccharide acemannan.
1.2 Applications of A. vera Mucilaginous Gel or Fractions
A. vera mucilaginous gel is considered to be a potential source of natural polymers, having numerous applications in food, medicines and cosmetic products due to the presence of seventy-five potentially bioactive molecules, such as polysaccharides, proteins and glycoproteins [18, 29].
Acemannan alone was used in wound care pharmaceuticals and alveolar osteitis patients as Acemannan Hydrogel™ [4, 10] as well as Acemannan immunostimulantTM, used in fibrosarcoma treatment in cats and dogs [4, 21], and also in other products like Immuno-10 [38, 39], Alcortin® [38], and Mole-Cure® [40].
In this context, due the Aloe polysaccharides having the ability to swell, water retention capacity, or ability to adsorb organic molecules such as fatty acids [7, 20], represents a potential microencapsulation agent through spray drying process to produce functional food containing bioactive labile compounds, such as gallic acid and curcumin [41, 42].
The use of edible films in fruit has been applied to substitute fungicides, consisting of single biopolymers or combinations to other biopolymers, lipids, polysaccharides and proteins. These films can reduce the loss of water and respiration rate, besides showing antioxidant effects and potentially reducing the occurrence of damage and pathogens. There are several studies with A. vera mucilaginous gel as edible coating applied to fruit, such as bananas, apricots, strawberries, raspberries and papayas, maintaining quality and increasing their shelf life [43–45].
A. vera has also been extensively explored, along with other biomaterials, for application to tissue engineering. A. vera polymers have potential use as biomaterial due to advantages such as biodegradability, oxygen permeability, and antioxidant activity, as well as regeneration and cell proliferation stimulant properties. These extracts are also economical and show low toxicity [46].
Based on the previously mentioned properties, recent research on the use A. vera gel investigate its use conjugated to natural and synthetic polymers in order to produce 2D and 3D matrices, such as hydrogels, microspheres, sponges, nanofibers and functional films [47–50]. A large part of these biomaterials has been prepared by combining A. vera gel with cellulose, chitosan, alginates, gellan gum, tragacanth gum, poly(e-caprolactone), jelly, collagen and glucan [50–59].
1.3 Aloe vera Gel Processing
The process of obtaining the mucilaginous gel of A. vera entails essentially the same procedure, with one or two variations. The standard procedure includes: harvesting the leaves, washing, removal of the rind (skin), elimination of the yellow sap (exudate), filleting, homogenization (grinding, pressing or extrusion), followed by filtration or centrifugation to remove fibrous material, and stabilization of the gel, through concentration by rotary evaporation, drying and sterilization (Table 1.1).
Table 1.1 Process for obtaining mucilaginous gel, polysaccharide fraction, oligosaccharides, |and acemannan.
Raw material
Techniques applied
References
Mucilaginous gel
Homogenization
Filleting
[7, 9, 20, 22, 30]
Pressing
[13, 26–28, 63]
Grinding
[4, 7, 14, 24–26, 30, 34, 37, 60, 61, 72–75]
Extrusion
[9]
Separation of insoluble fibers
Filtration
[26, 27, 34, 66, 75]
Centrifugation
[4, 13, 14, 37, 63, 72, 75]
Sterilization
Pasteurization
[7, 26]
High hydrostatic pressure treatment
[60, 61]
Drying
Concentration by rotary evaporation
[26–28, 34]
Freeze drying
[13, 20–22, 24–28, 75]
Spray drying
[27, 28, 72]
Hot-air drying
[20, 22, 26]
Refractance window-drying and radiant zone-drying
[27, 28]
FIR radiation and HVEF assisted hot air drying
[30]
Polysaccharide Fraction
Alcohol precipitation
[4, 7, 67, 9, 13, 20, 22, 27, 34, 37, 66]
Dialysis
[13, 68, 70]
Freeze drying
[4, 22, 37, 68]
Hot air drying
[13, 34]
Grinding
[5, 13]
Ammonium sulfate precipitation
[67]
Purified acemannan
Alcohol precipitation
[5, 14, 30, 69]
Dialysis
[5, 7, 20, 27, 30, 34, 69]
Freeze drying
[14, 20, 30, 34, 69]
Anion-exchange chromatography
[5, 34]
Gel-permeation chromatography
[7, 20, 27, 34]
Ionic liquid-based aqueous two-phase system
[69]
Aqueous two-phase system
[71]
Membrane separation
[71]
Oligosaccharides
Homogenization
[76]
Centrifugation
[76]
Dialysis
[40]
Freeze drying
[40]
Membrane fractionation
[76]
Size-exclusion chromatography
[11]
Gel-permeation chromatography
[40, 76]
A. vera rapidly degrades and therefore suitable techniques should be applied after harvesting to prolong the half-life of the product, such as preserving and transporting the leaves at low temperatures [24, 25]. Better results are achieved when the plant is processed immediately after harvesting. This is because the steady decomposition of the gel commences with natural enzymatic reactions, as well as microbial growth, due to the presence of oxygen [17].
The filtering process can involve filtration with activated charcoal filters, intended to decolorize the gel and remove anthraquinones, especially if the gel is intended for internal use, owing to the laxative properties of these substances [17, 34]. Several filtration steps ensue which may involve course screening filters (400–800 µm) and finer filters (25–100 µm) [27] to remove insoluble fibrous material.
Sterilization and stabilization techniques are used [17, 29] to prevent oxidation, decomposition, and loss of active substances. Sterilization can be performed by means of cold processes, using enzymes, UV light and microfiltration, or hot processes, such as pasteurization [17].
