Chapter 1
Bioactive Volatile Compounds from Plants An Overview Roy Teranishi and Saima Kint
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Western Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, 800 Buchanan Street, Albany, CA 94710
Volatiles from plants have been used for perfumes and incense since ancient times. Today, the perfume industry incorporates extensive research on plant volatiles. Flavor chemists also study and use volatiles from plants to improve food quality. The vast information accumulated by perfume and flavor chemists forms an excellent base of knowledge for studying plant-insect interactions. The following is an overview on subsequent chapters which discuss some of the latest methods and equipment in sample preparation, analyses and identifications of volatiles from various flowers, leaves, and fruits. Also, activities other than olfactory responses, such as bacterial growth inhibition and increase or decrease of motor activity, are briefly reviewed. Plants, either directly or indirectly, are probably most important to man as a source of food. Man also depends on plants for sources of medicine (7). Although the human being no longer utilizes chemical communication for survival, in ancient times, volatiles from some plants were used as incense and perfumes and were highly prized, valued as precious as gold. For example, the Wise Men who came to worship the newborn Jesus brought gold, frankincense, and myrrh as gifts (2). Incense was burned on altars to the gods (5). Perfumery was probably started centuries before the Christian era (4). In modern times, perfumery has become a large industry, and the intricate art, science, and technology are described in a recent book (5). The chemistry of perfumes is complex and elegant (J, 6). Early studies on terpenes established a better understanding of chemical bonding and molecular rearrangements in volatile compounds (7). Chemical Communications Most people are pleased with the fragrance of flowers, the smell of grass, the aroma of a pine forest. This human response is an indirect use of odors to
This chapter not subject to U.S. copyright Published 1993 American Chemical Society
In Bioactive Volatile Compounds from Plants; Teranishi, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1993.
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convey a message and is the conceptual basis of the perfume industry. Chemical communication, however, does play an explicit role in lower animal forms: in search for food and mates, and in the avoidance of predators and danger. In the last few decades, much has been learned about chemical communications during insect-insect interactions and about pheromones which evoke responses among insects of the same species (8-16). Now research emphasis is directed towards insect-plant interactions (77, 78). In order to study and identify the volatiles from plants which evoke various responses in insects, we must turn to knowledge gained from perfume and flavor studies. Perfume chemists have identified and catalogued tens of thousands of compounds; flavor chemists, about 5,000 compounds.
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Experimental Some essential oils have aromas which seem to have no relationship to the plants from which they were obtained. In recent years, studies have attempted to identify the numerous compounds emanated from flowers and other parts of living plants (19). Some recent advances in capturing volatiles from living plants are covered in this book. To investigate plant-insect interactions, information from such studies is absolutely necessary. Correlating insect responses to specific compounds requires the knowledge of volatiles released by living plants. It is now known that plants release a range of concentrations of various compounds during different times of the day (20) and at different stages of fruit maturity (27). Upon fruit maceration, some compounds are released completely in a matter of minutes (22, 25). Steam distillation and extraction methods have yielded essential oils from many plants and have generated much useful information. Advances in instrumentation and analytical methods now permit spectral analyses of very small quantities. Headspace volatiles were analyzed as early as 30 years ago by gas chromatography (24). Today, the combination of gas chromatography/mass spectrometry is used routinely. It is now possible to obtain infrared (25) and nuclear magnetic resonance (26) data on material separated with fused silica capillary columns. Results obtained with state-of-the-art separation techniques and instrumentation for sample preparation and analyses are discussed in this book. The differences in aromas obtained by different isolation methods are compared. Discussion Until recently the predominant sources of volatiles for perfumes have been essential oils and synthetic materials. It has been shown that there are considerable differences between volatiles from living and picked material from a certain plant and the essential oils obtained from the same plant by distillation or extraction (19). Because it is the dream of some perfumers to capture the freshness of living flowers, there is a growing interest in headspace analyses of living flowers and in vacuum headspace analyses of freshly cut flowers. Some advantages and disadvantages of such methods are discussed in this book. Citrus fruit juices are freshly squeezed onto some foods for tartness and for
In Bioactive Volatile Compounds from Plants; Teranishi, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1993.
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fresh aroma. Extensive effort has been made to identify the compounds which contribute to this fresh quality. Again, the advent of new methods and equipment permit the investigation of such labile qualities. Studies of several citrus flowers and fruit are described in several chapters of this book. Not only are the differences in volatiles from flowers from different species catalogued and described, but analytical methods have also been developed to such an extent that varietal differences can be characterized. A considerable data base is being developed for chemotaxonomy. The use of attractive aromas from plants is not restricted to human beings. The age of indiscrimate use of non-selective, long lasting poisons for control of insects and weeds is slowly coming to an end after the plea by Rachel Carson (27) to use methods more compatible with the environment in which we live. "Through all these new, imaginative, and creative approaches to the problem of sharing our earth with other creatures there runs a constant theme, the awareness that we are dealing with life — with living populations and all their pressures and counterpressures, their surges and recessions. Only by taking account of such life forces and by cautiously seeking to guide them into channels favorable to ourselves can we hope to achieve a reasonable accommodation between the insect hordes and ourselves..." (27). The use of insect attractants, not just pheromones, is merely beginning. We must find subtle ways to control insects by studying the plant-insect interactions and then intercede at vulnerable steps. To do so, we must study how specific plant volatiles modify the behavior of specific insects. The information accumulated by perfume and flavor chemists serves as a data base for such studies. Information gained from the biosynthesis of terpenes which attract insects is also very valuable. In the world of medicine, it is well known that strong drugs may have detrimental side effects. Perhaps we should rely less on the pharmaceutical industry and use more subtle methods correlated with plant science. The inhibition of bacterial growth by some terpenoid compounds is well known. Plant volatiles have been used since ancient times for soothing and promoting sleep. Now there is quantitative data on some volatile compounds which decrease or increase motor activity. Some interesting information in aromatherapy is given in this book. It would take many volumes to cover all of the bioactivity evoked by plant volatiles. In this volume, we present some of the exciting topics under study on volatiles from flowers and other parts of plants by perfume and flavor chemists, together with the methods developed for isolating volatiles from living plants, and a very brief look at some bioactive aspects of such volatiles. It is hoped that this information will serve as a beginning for plant-insect interaction studies. Literature Cited 1. 2.
Shultes, R. Ε. In Plants in the Development of Modern Medicine; Swain, T., Ed.; Harvard University Press: Cambridge, MA, 1972; pp 103-124. Matthew. In the New Testament, The Holy Bible, American Revision; Thomas Nelson & Sons: New York, NY, 1901; 2, pp 11.
In Bioactive Volatile Compounds from Plants; Teranishi, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1993.
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3. 4. 5. 6. 7.
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Stoddart, D. M. The Scented Ape; Cambridge University Press: Cambridge, MA, 1990; pp 168-206. Roudnitska, E. In Perfumes: Art, Science and Technology; Müller, P. M.; Lamparsky, D., Eds.; Elsevier Applied Science: London, 1991; pp 3-48. Perfumes: Art, Science and Technology; Müller, P. M.; Lamparsky, D.; Eds.; Elsevier Applied Science: London, 1991; pp 658. Ohloff, G. Riechstoffe und Geruchssinn; Springer-Verlag: New York, NY, 1990; pp 233. Ruzicka, L. In Perspectives in Organic Chemistry; Todd, Α.; Ed.; Interscience: New York, NY, 1956; pp 265-314. Jacobson, M. Insect Sex Pheromones; Academic Press, New York, 1972; pp 1-382. Pheromones; Birch, M. C., Ed.; North-Holland Publishing Company: Amsterdam, 1974; pp 1-495. Introduction to Insect Pest Management; Metcalf, R. L.; Luckmann, W. H.; Eds.; John Wiley and Sons: New York, NY, 1975; pp 1-587. Chemicaontrol of Insect Behavior: Theory and Application; Shorey, H. H.; McKelvey, J. J., Jr.; Eds.; John Wiley and Sons: New York, NY, 1977; pp 1-414. Insect Suppression with Controlled Release Pheromone Systems; Kydonieus, A. F.; Beroza, M.; Zweig, G.; Eds.; CRC Press, Inc.: Boca Raton, FL, 1982; vol 1, pp 1-274, vol 2, pp 1-312. Techniques in Pheromone Research; Hummel, H. E.; Miller, Τ. Α.; Eds.; Springer-Verlag, New York, NY, 1984; pp 1-446. CRC Handbook of Natural Pesticides, Volume IV, Pheromones, Part A; Morgan, E. D.; Mandava, Ν. B.; Eds; CRC Press, Inc.: Boca Raton, FL, 1988; pp 1-203. CRC Handbook of Natural Pesticides, Volume IV, Pheromones, Part B; Morgan, E. D.; Mandava, Ν. B.; Eds.; CRC Press, Inc.: Boca Raton, FL, 1988; pp 1-291. Handbook of Insect Pheromones and Sex Attractants; Mayer, M. S.; McLaughlin, J. R.; Eds.; CRC Press, Inc. Boca Raton, FL, 1991; pp 11083. Semiochemicals: Their Role in Pest Control; Nordlund, D. Α.; Jones, R. L.; Lewis, W. J.; Eds.; John Wiley and Sons: New York, NY, 1981; pp 1-306. CRC Handbook of Natural Pesticides: Volume VI, Insect Attractants and Repellents; Morgan, E. D.; Mandava, Ν. B.; Eds.; CRC Press, Inc.: Boca Raton, FL, 1990; pp 1-249. Mookherjee, B. D.; Wilson, R. Α.; Trenkle, R. W.; Zampino, M. J., Sands, K. P.; Flavor Chemistry: Trends and Developments; ACS Sym posium Series 388; American Chemical Society: Washington, DC, 1989; pp 176-187. Loper, G. M.; Berdel, R. L. Crop Science; 1978, vol 17, pp 447-452. Engel, K.-H.; Ramming, D. W.; Flath, R. Α.; Teranishi, R. J. Agric. Food Chem., 1988, vol 36, pp 1003-1006.
In Bioactive Volatile Compounds from Plants; Teranishi, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1993.
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Drawert, F.; Kler, Α.; Berger, R.G. Lebensm.-Wiss. u.-Technol. 1986, vol 19, pp 426-431. Buttery, R. G.; Teranishi, R.; Ling, L. C. J. Agric. Food Chem.; 1987, vol 35, pp 540-544. Teranishi, R.; Buttery, R. G. Volatile Fruit Flavors; International Feder ation of Fruit Juice Producers Symposium, Bern, Switzerland; Juris-Verlag: Zürich, 1962; pp 257-266. Williams, Α.Α.; Tuchnott, O. G.; Lewis, M. J.; May, H.; Wachter, L. In Flavor Science and Technologie; Martens, M.; Dalen, G. Α.; Russwurm, Jr., H.; Eds.; John Wiley & Sons: Chichester, 1987, pp 259-270. Etzweiler, F. J. High Res. Chrom. & Chrom. Comm. 1988, pp 449-456. Carson, R. Silent Spring; Houghton Miffin Co: Boston, MA, 1962; 368 pp.
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In Bioactive Volatile Compounds from Plants; Teranishi, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1993.