ABSTRACT
Essential oils are odorous principles stored in special plant cells—glands, glandular hairs, oil ducts or resin ducts—situated in any part of a plant or its exudations. These oils are responsible for the distinctive aromas associated with individual plant species. Essential oil composition can vary according to geographic and genetic factors, even though the same botanic species is involved—a phenomenon known as chemical polymorphism. When this occurs a terminology can be used where the Latin name is followed by the name of the chemical component most characteristic for that particular race of the plant, that is, its chemotype, for example Thymus vulgaris linalol, Thymus vulgaris thymol. Essential oils are readily absorbed into the body and across the blood–brain barrier because of their small molecular size and strong lipophilic nature. Compared to other compounds the therapeutic action of essential oils can be anticipated by knowledge of their chemistry—based primarily on the functional groups.
