Water Extraction of Bioactive Compounds

From Plants to Drug Development

Herminia Dominguez, Maria Jesus Gonzalez Munoz

• Publisher: Elsevier
• Year: 2017
• Print ISBN: 9780128093801
• eBook ISBN: 9780128096154
• Topic: Scienze fisiche
• Subtopic: Chimica

Water Extraction of Bioactive Compounds: From Plants to Drug Development draws together the expert knowledge of researchers from around the world to outline the essential knowledge and techniques required to successfully extract bioactive compounds for further study. The book is a practical tool for medicinal chemists, biochemists, pharmaceutical scientists and academics working in the discovery and development of drugs from natural sources.The discovery and extraction of bioactive plant compounds from natural sources is of growing interest to drug developers, adding greater fuel to a simultaneous search for efficient, green technologies to support this. Particularly promising are aqueous based methods, as water is a cheap, safe and abundant solvent. Water Extraction of Bioactive Compounds: From Plants to Drug Development is a detailed guide to the fundamental concepts and considerations needed to successfully undertake such processes, supported by application examples and highlighting the most influential variables.Beginning with an introduction to plants as sources of drugs, the book highlights the need for a move towards both more rational and greener techniques in the field, and presents multiple innovative water-based strategies for the discovery and extraction of bioactive constituents of botanicals. A broad range of available techniques are reviewed, including conventional and pressurized hot water extraction techniques, intensified processes such as microwave-assisted, ultrasound-assisted processes, and enzyme assisted extraction, and processes using combined techniques.- Covers the theoretical background and range of techniques available to researchers, helping them to select the most appropriate extraction method for their needs- Presents up-to-date and cutting edge applications by international experts- Highlights current use and future potential for industrial scale applications- Offers a thorough introduction to plants as sources of drugs, highlighting strategies for the discovery of novel bioactive constituents of botanicals

Chapter 1

Introduction

Beatriz Díaz Reinoso, María Jesús González Muñoz, and Herminia Domínguez González Universidade de Vigo (Campus Ourense), Ourense, Spain

Abstract

Numerous industrial sectors such as the food, nutraceutical, cosmetic, and pharmaceutical have increasingly changed to the natural plant-based active molecules in detriment of synthetic compounds. This chapter presents a survey of the major components in vegetal materials, with special emphasis on bioactives, the fundamentals of solid-liquid extraction processes, and the physical and biotechnological strategies proposed to enhance the process performance and the product quality, as well as the possibility of utilizing the by-products in a biorefinery approach.

Keywords

Botanical bioactives; Extraction; Intensification

1. Botanical Therapy

1.1. Plant Constituents and Biological Actions

Several classifications of plant constituents can be established depending upon the particular criteria used. Approaches based on biosynthetic pathways or chemically related structures and on pharmacological or toxicological effects are not coincident (Bernhoft, 2010). According to a commonly used categorization, plant chemicals can be classified depending on their role in plant metabolism in (1) primary metabolites, aimed at growth and development, such as carbohydrates, aminoacids and proteins, and lipids, and (2) secondary metabolites, involved in specific functions, often produced in a phase subsequent to growth, and may have survival function in defense against predators, pathogens, and abiotic stresses like UV light, ozone, and herbicides (Harborne, 1993; Croteau et al., 2000).

Secondary plant metabolites, which have key functions, can be divided into three major groups: terpenoids, phenolic compounds, and alkaloids. Phenolics protect against free radicals generated during photosynthesis; terpenoids may attract pollinators or inhibit competing plants; alkaloids ward off herbivores or insect attacks. Other secondary metabolites act as cellular signaling molecules or have other functions in the plants (Bernhoft, 2010). Secondary metabolites are often formed as mixtures of closely related members of a chemical family, biosynthesized from primary substances, such as amino acids and carbohydrates through methylation, hydroxylation, and glycosylation (Korkina and Kostyuk, 2012). There are four major pathways for synthesis of secondary metabolites: (1) shikimic acid pathway, (2) malonic acid pathway, (3) mevalonic acid pathway, and (4) non-mevalonate pathway (Tiaz and Zeiger, 2006; Azmir et al., 2013). Alkaloids are produced by aromatic amino acids (from shikimic acid pathway) and by aliphatic amino acids (from tricarboxylic acid cycle), whereas phenolic compounds are synthesized through shikimic acid pathway and malonic acid pathway. Phenolic compounds contain phenol groups and can be simple or complex structures. Flavonoids consist of a central three-ring structure and can be found polymerized as proanthocyanidins. Both groups of compounds can occur as glycosides. Condensed tannins are large polymers of flavonoids and hydrolysable tannins are polymers composed of a carbohydrate whose hydroxyl groups are partially or totally esterified with phenolic groups, gallic acid in gallotannins, and ellagic acid in ellagitannins. Terpenoides are synthesized via the five-carbon building block isoprene. These compounds are lipophilic, and have strong odors and flavors. Monoterpenoids consist of two isoprene units and sesquiterpenoids of three units. They are referred to as low-molecular-weight terpenoids and represent a highly diverse category of plant constituents. Glycosides are bound to a mono- or oligosaccharide or to uronic acid. The main groups of glycosides are cardiac glycosides, cyanogenic glycosides, glucosinolates, saponins, and anthraquinone glycosides. The glucosinolates present sulfur-containing, pungent amino acid-derived aglycones. Alkaloids are heterocyclic nitrogen containing compounds, usually with potent activity and bitter taste. They are of limited distribution in the plant kingdom and have diverse clinical properties.

The typical definitions of bioactive compounds in plants refer to secondary plant metabolites eliciting pharmacological or toxicological effects in man and animals (Gry et al., 2007; Bernhoft, 2010). The presence of bioactives can largely explain the epidemiological evidence for the health benefits derived from a diet rich in fruit and vegetables, correlated with reduced risk of the development of chronic disorders, such as cardiovascular diseases and cancer. Although some nutrients show these effects when ingested at high dosages (e.g., vitamins and minerals), and other constituents, such as carbohydrates, peptides and lipids, have important bioactivity, nutrients in plants are generally not included in the term bioactive plant compound (Aluko, 2012). Most examples presented in this book are related to secondary metabolites, but also to those with nutritional function and confirmed beneficial effects, such as carbohydrates, peptides, and lipids.

1.2. Strategies in the Discovery of Novel Botanical Bioactives

Natural products have contributed substantially to drug discovery and health benefits; among them, plants are a rich source of botanical ingredients, with long tradition as medicine and health supplements used both in food and feed (Vinatoru, 2001; Aburjai and Natsheh, 2003; Schmidt et al., 2007; Risht...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• List of Contributors
• Foreword
• Preface
• Chapter 1. Introduction
• Chapter 2. Therapeutic Compounds From Plants Using Subcritical Water Technology
• Chapter 3. Hydrolysis of Biopolymers in Near-Critical and Subcritical Water
• Chapter 4. Subcritical Water Extraction and Neoformation of Antioxidants
• Chapter 5. Extraction of Oligosaccharides With Prebiotic Properties From Agro-Industrial Wastes
• Chapter 6. Microwave-Assisted Water Extraction
• Chapter 7. Microwave-Assisted Water Extraction of Carbohydrates From Unutilized Biomass
• Chapter 8. Microwave-Assisted Extraction of Flavonoids
• Chapter 9. Microwave-Assisted Extraction of Betalains
• Chapter 10. Microwave-Assisted Pressurized Hot Water Extraction of Alkaloids
• Chapter 11. Fundamentals of Ultrasound-Assisted Extraction
• Chapter 12. Ultrasound-Assisted Extraction of Bioactive Carbohydrates
• Chapter 13. Enzyme-Assisted Aqueous Extraction Processes
• Chapter 14. Enzyme-Assisted Extraction of Phenolic Compounds
• Chapter 15. Silymarin Extraction From Silybum marianum L. Gaertner
• Chapter 16. Potential of Novel Technologies for Aqueous Extraction of Plant Bioactives
• Chapter 17. Combination of Water-Based Extraction Technologies
• Index