essential oils, volatile oils that occur in plants and in general give to the plants their characteristic odors, flavors, or other such properties. Essential oils are found in various parts of the plant body (in the seeds, flowers, bark, or leaves) and are also concentrated in certain special cells or groups of cells (glands). Because of their properties, they are widely used in perfumes, flavorings, and medicines. Their chemical composition differs: A great many, for example, are principally terpenes, compounds of carbon and hydrogen. Others contain aldehydes, ketones, or phenols. Oxygen, sulfur, and nitrogen are present in compounds in others. In general, they are complex mixtures. They are obtained from the plant in various ways, depending upon the nature of the part in which they occur—by compression, by distillation with steam, by dissolving the oils out (extraction) or absorbing them, and by pressure and maceration. Among the plants notable for their essential oils are members of the following plant families: carrot (e.g., anise, dill, angelica), ginger (cardamom), heath (wintergreen), laurel (cinnamon and camphor), mint (pennyroyal, peppermint, spearmint, thyme), myrtle (clove and eucalyptus), olive (jasmine and lilac), orchid (vanilla), pulse (acacia and sweet pea), rose (attar of roses and almond), and rue (lemon and other citrus plants).
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.