Handbook of Essential Oils: Science, Technology and Applications by K. Hüsnü Can Başer and Gerhard Buchbauer. Boca Raton, FL: CRC Press; 2010. Hardcover; 975 pages. ISBN: 978-1-4200-6315-8. $229.95.

This imposing and impressive multi-author tome reviews the intricacies and scientific challenges of essential oils, those ethereal molecules produced by odiferous plants that form the most structurally diverse class of natural products from plants. The book additionally examines the controversial and frequently misunderstood branch of herbal phytotherapy based upon their use.

The editors have assembled an impressive array of authorities, addressing various topics of interest in 21 chapters that cross numerous disciplines. In early chapters, the reader learns a bit of the history of essential oils and their plant sources, indicating an early fascination by our forebears in these scented liquids and how to squeeze them from citrus peels or distill them from “secretory idioblasts” or glandular trichomes in leaves, flowers, bark, or pine needles. The reader discovers that a given species is not only capable of producing myriad chemotypes with different odors and chemical composition, but also that a single plant may demonstrate phytochemical polymorphism in its production of essential oils in different structures. These processes are subject to environmental influences but depend, above all, on the plant’s genetic endowment, thus allowing for the selective breeding or vegetative propagation of plants with better smells and more interesting therapeutic potential.

Chapter 5, written by Charles Sell and focusing on chemistry, is filled with interesting facts, ranging from ancient concepts that essential oils captured the quintessential life force or spirit of plants to their biosynthetic genesis. He subsequently documents the potency of essential oils. Where someone may be impressed by a 1% yield of an alkaloid in a medicinal plant, terpenoid components above a concentration as little as 0.05% may be distinctly active physiologically.

Essential oil safety is covered in a relatively short chapter, although it is reassuring in noting that oils derived from food plants generally have a comfortable presumption of low toxicity. Readers particularly concerned with this subject would be wise to consult a dedicated text.¹ Metabolism, mostly hepatic, via oxidation, reduction, and hydrolysis, is well described.

Gerhard Buchbauer’s chapter on biological activity is a highlight, containing valuable documentation and references on the mechanisms of potential essential oil activity to combat cancer, kill viruses, reduce inflammation, increase skin penetration by other pharmacological agents, reduce lipid peroxidation in foods, and act as general anti-oxidants that potentially may be useful in various diseases of aging

The chapter on central nervous system effects by Eva Heuberger and a group of Brazilian scientists does an able job of tackling the very difficult topic of terpenoid psychopharmacology, previously addressed by others.^2,3,4 Much of this material is not for the faint of heart— trying to assess the pertinence of minor changes contingent negative variation and other neurophysiological tests. Ultimately, there are few hard and fast conclusions. The subjective experience one individual derives from a specific scent exposure may contrast quite markedly from another. One person’s elated memory of childhood summer visits to grandmother’s cottage on Nantucket elicited by lavender scent may be hard to reconcile with another’s bored sedation by the same olfactory stimulus. Past experience and current set and setting figure prominently in the resulting mind states after exposure. Both animal and human clinical data are included. Some evidence is quite compelling: the ability of ambient citrus scent to allow hospitalized patients in Japan to discontinue antidepressant medication⁵ is one striking example of the potential therapeutic power of essential oils.

Bob Harris’ entry on phytotherapeutic uses will be of great interest to HerbalGram readers, providing a very accessible and nicely organized presentation of myriad uses for essential oils, including treatment of ticks and mites, their ability to inactivate enveloped viruses outside the cell, benefits for motion sickness (ginger, lavender, and mints) and menstrual cramps (fennel), and use of 1,8-cineole preparations to allow reduction of prednisone use in asthma.

The antimicrobial activities of terpenoids are handled with an introduction, in which thymol’s (an ingredient in Listerine^®) activity is stated as 10-fold stronger than phenol. This is followed by an astounding 177 pages of tables documenting previous experimental work examining the effects of various agents.

Maria Lis-Balchin provides a masterful critical analysis of the scientific validity or lack thereof in previous aromatherapy publications. The failure of many previous experiments to demonstrate sufficient scientific rigor is discussed, along with the challenges inherent in attempting randomized clinical trials with such agents, due in no small part to difficulties in adequately blinding subjects to interventions with obvious distinctive organoleptic properties, and the ability to evoke strong emotions and regenerate long-lost memories and associations. While some may be disappointed that their treasured beliefs about the healing magic of essential oils may be deflated by such revelations, others will be heartened by appropriate credit given where due, such as in some well controlled studies with benefit of Melissa officinalis (Lamiaceae) on agitation in elderly people with dementia.

Two chapters on in vivo biotransformations (mostly extra-mammalian) of mono- and sesquiterpenoids will be of greatest interest to sub-specialists. Subsequent entries on industrial uses for perfumes, encapsulation and other methods of delivery, use in cuisine (replete with recipes), veterinary application, trade and storage and transport, European Union legislation, and allergenicity round out the volume nicely, and are filled with fun facts ready to cite at your next herbal social opportunity.

Some pros and cons: This is a monumental reference work, and as such, most will pick and choose their areas of greatest interest, with few reading cover to cover. As is frequently the case in edited texts, the writing styles and qualities are uneven at times. The few idiomatically-challenged entries are offset by the highly entertaining prose of the outstanding selections. The book is inconsistent in its presentation of plant species (lower or upper case, Italic or Roman), contains a fair number of typographical errors, and occasional missing references from the text or bibliographies. The alphabetization of the latter is imperfect.

The book’s scope is very effective in covering major aspects of the field, but the discussion draws the line at mono- and sesquiterpenoids, not addressing diterpenoid and higher molecular weight entities. The index is reasonably composed, allowing most subjects of interest to be accessed quickly. The book contains extremely detailed tables with a wealth of information that would be extremely challenging to access elsewhere. I would have liked to see inclusion of a comprehensive listing of major essential oil plants and their range of terpenoid components, but much of this can be extracted by careful review of the contents or in other references.^1,6

Finally, I saw no mention of a key research finding: β-caryophyllene, a sesquiterpenoid common to cannabis, black pepper and Peruvian balsam, that has recently been demonstrated as a potent and highly selective agonist of the CB2 (cannabinoid) receptor,⁷ suggesting its possible utility in a variety of inflammatory and pain conditions, as well as primary treatment of some cancer cell types. This highlights how much we have yet to learn about the peculiar phytochemistry of essential oils and the therapeutic possibilities of these fascinating and alluring scents.

—Ethan Russo,
MD Senior Medical Advisor,
GW Pharmaceuticals
Vashon Island, WA

References

1. Tisserand R, Balacs T. Essential Oil Safety: A Guide for Health Care Professionals. Edinburgh: Churchill Livingstone; 1995.
2. Lawless J. Aromatherapy and the Mind: An Exploration into the Psychological and Emotional Effects of Essential Oils. London: Thorsons; 1994.
3. Russo EB. Handbook of Psychotropic Herbs: A Scientific Analysis of Herbal Remedies for Psychiatric Conditions. Binghamton, NY: Haworth Press; 2001.
4. Bowles EJ. The Chemistry of Aromatherapeutic Oils. 3rd ed. Crow’s Nest, NSW, Australia: Allen & Unwin; 2003.
5. Komori T, Fujiwara R, Tanida M, Nomura J, Yokoyama MM. Effects of citrus fragrance on immune function and depressive states. Neuroimmunomodulation. 1995;2(3):174-80.
6. Lawless J. The Illustrated Encyclopedia of Essential Oils : The Complete Guide to the Use of Oils in Aromatherapy and Herbalism. Shaftesbury, Dorset, [England]; Rockport, MA.: Element; 1995.
7. Gertsch J, Leonti M, Raduner S, et al. Beta-caryophyllene is a dietary cannabinoid. Proc Natl Acad Sci USA. 2008;105(26):9099-104.