K. Hüsnü Can Basher and Gerhard Buchbauer
Essential oils (EOs) are very interesting natural plant products and among other qualities they possess various biological properties. The term "biological" comprises all activities that these mixtures of volatile compounds (mainly mono- and sesquiterpenoids, benzenoids, phenylpropanoids, etc.) exert on humans, animals, and other plants. This book intends to make the reader acquainted with all aspects of EOs and their constituent aromachemicals ranging from chemistry, pharmacology, biological activity, production, and trade to uses, and regulatory aspects. After an overview of research and development activities on EOs with a historical perspective (Chapter 2), Chapter 3 "Sources of Essential Oils" gives an expert insight into vast sources of EOs. The chapter also touches upon agronomic aspects of EO-bearing plants. Traditional and modern production techniques of EOs are illustrated and discussed in Chapter 4. It is followed by two important chapters "Chemistry of Essential Oils" (Chapter 5) and "Analysis of Essential Oils" (Chapter 6) illustrating chemical diversity of EOs, and analytical techniques employed for the analyses of these highly complex mixtures of volatiles.
They are followed by a cluster of articles on the biological properties of EOs, starting with "The Toxicology and Safety of Essential Oils: A Constituent-Based Approach" (Chapter 7). On account of the complexity of these natural products, the toxicological or biochemical testing of an EO will always be the sum of its constituents which either act in a synergistic or in an antagonistic way with one another. Therefore, the chemical characterization of the EO is very important for the understanding of its biological properties. The constituents of these natural mixtures upon being absorbed into the blood stream of humans or animals get metabolized and eliminated. This metabolic biotransformation leads mostly in two steps to products of high water solubility which enables the organism to get rid of these "xenobiotics" by renal elimination. This mechanism is thoroughly explained in Chapter 8, "Metabolism of Terpenoids in Animal Models and Humans." In Chapter 9, "Biological Activities of Essential Oils," "uncommon" biological activities of EOs are reviewed, such as anticancer properties, antinociceptive effects, antiviral activities, antiphlogistic properties, penetration enhancement activities, and antioxidative effects. The psychoactive, particularly stimulating, and sedative effects of fragrances as well as behavioral activities, elucidated, for example, by neurophysi-ological methods, are the topics of Chapter 10 ("Effects of Essential Oils in the Central Nervous Systemd"), Section 10.2. Here, the emphasis is put on the central nervous system and on psychophar-macology whereas Chapter 10, Section 10.1 mainly deals with reactions of the autonomic nervous system upon contact with EOs and/or their main constituents. The phytotherapeutic uses of EOs is another overview about scientific papers in peer-reviewed journals over the last 30 years, so to say the medical use of these natural plant products excluding aromatherapeutical treatments and single case studies (Chapter 11, "Phytotherapeutic Uses of Essential Oils"). Another contribution only deals with antimicrobial activities of those EOs that are monographed in the European Pharmacopoeia. In Chapter 12, "In Vitro Antimicrobial Activities of Essential Oils Monographed in the European Pharmacopoeia 6th Edition," more than 81 tables show the importance of these valuable properties of EOs. Aromatherapy with EOs covers the other side of the "classical" medical uses. "Aromatherapy with Essential Oils" (Chapter 13), is written by Maria Lis-Balchin, a known expert in this field and far from esoteric quackery. It completes the series of contributions dealing with the biological properties of EO regarded from various sides and standpoints.
Chapters 14 and 15 by the world-renown experts Y. Asakawa and Y. Noma are concise treatises on the biotransformations of EO constituents. Enzymes in microorganisms and tissues metabolize EO constituents in similar ways by adding mainly oxygen function to molecules to render them water soluble to facilitate their metabolism. This is also seen as a means of detoxification for these organisms. Many interesting and valuable novel chemicals are biosynthesized by this way. These products are also considered as natural since the substrates are natural.
Encapsulation is a technique widely utilized in pharmaceutical, chemical, food, and feed industries to render EOs more manageable in formulations. Classical and modern encapsulation techniques are explained in detail in Chapter 17, "Encapsulation and Other Programmed Release techniques for EOs and Volatile Terpenes."
EOs and aromachemicals are low-volume high-value products used in perfumery, cosmetics, feed, food, beverages, and pharmaceutical industries. Industrial uses of EOs are covered in an informative chapter from a historical perspective.
"Aroma-Vital Cuisine" (Chapter 18) looks at the possibility to utilize EOs in the kitchen, where the pleasure of eating, the sensuality, and the enjoyment of lunching and dining of mostly processed food are stressed. Here, rather the holistic point of view and not too scientific way of understanding EOs is the topic, simply to show that these volatile natural plant products can add a lot of well-feeling to their users.
EOs are not only appealing to humans but also to animals. Applications of EOs as feed additives and for treating diseases in pets and farm animals are illustrated in Chapter 19, "Essential Oils Used in Veterinary Medicine," that comprises a rare collection of information in this subject.
The EO industry is highly complex and fragmented and the trade of EOs is rather conservative and highly specialized. EOs are produced and utilized in industrialized as well as in developing countries worldwide. Their trade situation in the world is summarized in "Trade of Essential Oils" (Chapter 20), authored by a world-renown expert Hugo Bovill.
Storage and transport of EOs are crucial issues since they are highly sensitive to heat, moisture, and oxygen. Therefore, special precautions and strict regulations apply for their handling in storage and transport. "Storage and Transport of Essential Oils" (Chapter 21) will give the reader necessary guidelines to tackle this problem.
Finally, the regulatory affairs of EOs are dealt with in Chapter 22 in order to give a better insight to those interested in legislative aspects. "Recent EU Legislation on Flavors and Fragrances and Its Impact on Essential Oils" comprises the most up-to-date regulations and legislative procedures applied on EOs in the European Union.
This book is hoped to satisfy the needs of EO producers, traders, and users as well as researchers, academicians, and legislators who will find the most current information given by selected experts under one cover.
2 History and Sources of Essential Oil Research
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