Case Studies With Plant Fragrances

8.4.1 Sources of Plant Fragrances

Plant fragrances from flowers attract various kinds of pollinators, and other fragrances that come from both flowers and vegetative parts of plants deter predators (see Chapter 2). Many of these same fragrances from plants have utilitarian uses by humans, namely, perfumes, herbal teas, sachets, herbal wreaths, and insect repellents. We grow many fragrance herbs both commercially and in the home garden. Organic gardeners grow some of the insect-repelling herbs as companion plants with flowers and vegetables to repel insect predators. These plants include tansy (Tanacetum vulgare), chives (Allium schoenoprasum), and marigolds (Tagetes patula). The fragrances, themselves, have their origin from scent-producing cells in flower petals and other flower parts as well as from glandular hairs (trichomes) found on leaves, stems, and floral bracts.

8.4.2 Uses of Plant Fragrances

8.4.2.1 Sachets

Sachets are made of dried flowers and are placed in loosely woven cloth so that the fragrance can be smelled. They are used in bathrooms and bedrooms (e.g., in bedding) to provide pleasant smells, and in linen closets to repel moths that destroy wool and other cloth garments. Dried rose (Rosa spp.) petals are often used in sachets to provide pleasant aromas. Dried lavendar (Lavandula offici-nalis) flowers have essential oils that not only smell nice and clean (hence, their use in soaps and perfumes), but also, destroy bacteria that cause tuberculosis and typhoid fever.24

8.4.2.2 Pest Repellents

Classical pest repellents from plants come from rotenone (from roots of Derris sp.), pyrethrum flowers (a Chrysanthemum sp.), lemon grass (Cymbopogon citratus and C. flexuosus), tobacco (Nicotiana tabacum) that contains nicotine (now banned by the EPA because it is carcinogenic to humans), and garlic and chives (Allium sativum and A. schoenoprasum, respectively). In the home garden, organic gardeners use teas made from garlic juice or juice from chive plants to control insect pests.

8.4.3 Essay on Extraction and Analysis of Essential Oils from Lavendar (Lavandula officinalis)*

The objectives of this section are to gain background information on the medicinal and pesticidal properties of the herb Lavandula officinalis, Lavender, to form working hypotheses about its uses and to test these hypotheses. The hypotheses are as follows: (1) the essential oil of lavender works both as an insecticide and as a natural herbicide in the lavender plant; (2) mixed with another oil or cream, the essential oil works as an antibacterial ointment. Background information needed to formulate these hypotheses was obtained on the essential oil of lavender as used in traditional herbal medicine, the human uses of the essential oil in the lavender plant, the plant's ability to synthesize the essential oil, documentation of the constituents of the oil, and growing the lavender plant.

The essential oil of lavender is the main product of the plant that is used in herbal medicine. In traditional herbal medicine, the lavender oil is used as an antispasmodic, a carminative, a diuretic, a sedative, a stimulant, a stomachic, and a tonic to treat such ailments as acne, colic, flatulence, giddiness, migraines, nausea, rheumatism, spasms, sprains, toothache, and vomiting.25 Preparations of

* This section was prepared by Matthew Perry (Figures 8.11 and 8.12). Copyright © 1999 CRC Press, LLC.

the lavender oil to treat these ailments include infusions with water and mixtures with other oils or creams.

Lavender oil is also used as the component of several prepared sedatives and such as Sedatruw, Neroflux, Beruhigungstee Satus, Nerven-Schlaf-Tee, and Chol-truw.26 The greatest market for these products and the essential oil is in western Europe.

Lavender grows well and in abundance in western Europe, mainly France, Germany, and England. Lavender grows well in warm climates with sandy soil or soil that drains well. The plant does not need much water. However, it is necessary for lavender to have a cold season with freezing temperatures before it flowers again. Flowering usually occurs in late June to early July depending on the length of the winter. At this time, the essential oil, which is produced in the flowers, can be obtained.

The essential oil of lavender contains over 100 compounds, most of which are volatile and some of which are toxins or narcotics. Soxhlet extraction was used with hexane to obtain a mixture of hexane and essential oil from the flowers. A Shimadzu gas chromatograph was then used to document the constituents of the essential oil in lavender flowers (Figure 8.13). The documented chemicals (Table 8.3) concur with the chemicals listed in The Encyclopedia of Common Natural Ingredients Used in Food, Drugs, and Cosmetics (1996) by Albert Leung and Stephen Foster27 as constituents of the essential oil in lavender.

With the amount of toxins in lavender, the following hypotheses were formulated: (1) The essential oil of lavender works as an insecticide and as a natural herbicide in the lavender plant; and (2) mixed with another oil or cream, the essential oil could be used as an antibacterial ointment.

To test the second hypothesis, pure essential oil was needed from the flowers. To obtain this, steam distillation was used. This procedure resulted in a mixture of water and the essential oil. The mixture was then frozen to separate the water from the essential oil. The frozen mixture would then be melted with a hand or body lotion or cream and placed in a culture of bacteria to test the essential oil's ability to kill bacteria.

The result of the freezing, however, did not lead to the bacteria testing. The frozen mixture appeared to be two separate liquids, albeit both were clear. Unfortunately, a test tube of frozen water had an identical appearance to the frozen mixture of oil and water. Therefore the mixture could not be separated.

To test the first hypothesis, it would be necessary to place a number of plants in a controlled room with a large number of plant-eating insects. However, this hypothesis was never tested for lack of plants.

Since neither hypothesis was ever actually tested, no real conclusions can be made. However, the essential oil from lavender is known to be used as an antiseptic to treat eczema and cold sores.28 Also, it was observed in the greenhouse in which the lavender was kept, that the surrounding plants were covered with aphids and the lavender was untouched. Given this qualitative observation and the information provided in The Complete Medicinal Herbal,28 it can be inferred that these hypotheses are probably correct but further experimentation would be necessary.

FIGURE 8.11 Undergraduate student Matthew Perry holding a plant of lavendar, Lavandula officinalis; ca. 1/10 normal size. (Photo courtesy of David Bay.)
FIGURE 8.12 Undergraduate student Matthew Perry sitting next to a Shimadzu gas chromatograph/mass spectrometer used to analyze constituents in the essential oils he extracted from flowers of lavendar, Lavandula officinalis. (Photo courtesy of David Bay.)

From this point, there is much work that could be done. The first hypothesis could be fully tested. A way could be found to produce pure essential oil from the flowers of lavender. Then, the antibacterial ability of the essential oil could ill" " " ~ mwwH

FIGURE 8.13 Gas chromatography mass spectrometer trace of essential oil constituents (see Table 8.3) in flowers of lavendar, Lavandula officinalis.

FIGURE 8.13 Gas chromatography mass spectrometer trace of essential oil constituents (see Table 8.3) in flowers of lavendar, Lavandula officinalis.

be tested. It would be advantageous to obtain the required number of plants before beginning any experimentation. It would also be helpful to have a knowledge of the plants and their chemistry before starting any new experiments.*

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