One of the key families of aromatic compounds are a group of organic compounds known as terpenes. Most of the primary fragrances used in perfumery and aromatherapy alike are created through the use of terpenes. Unlike aldehydes, terpenes are typically naturally derived from botanical sources.
Structurally, terpenes are hydrocarbons that are comprised of five-carbon isoprene units that are combined to produce a great variety of skeletons. The function of these molecular structures can then be altered by the addition of enzyme groups.
Terpenes are the key flavor and aroma element in everything from perfume, to beer, wine and even cannabis. These highly aromatic compounds are naturally released by many plants as a deterrent for herbivores and parasites. These chemical signals are also believed to be attractive to predators of the insects that feed on the plants that produce them. The traditional use of citronella to repel insects is an excellent examples of their abilities.
In the wild, many forest give off a significant quantity of these chemicals. In fact, the hazy appearance of the Smoky Mountains in the American Southeast is due to a literal cloud of terpenes produced by the trees in the forests. These clouds can be intense enough to be categorized as "natural" air pollution.
Common botanical terpenes
2-Bornanone (camphor - resin of the camphor tree) has a eucalyptus-like scent and supports the micro circulation. It also has cooling, antiseptic effects.
(+)-Carvone (caraway oil, dill oil): releases a caraway-like scent
(-)-Carvone (crisped mint oil): The mirror image of (+)-carvone has a mint-like scent and also a highly allergenic potential
Carvenone (dill oil)
Fenchone (fennel oil, caraway oil)
ß-Ionone with a violet-like scent occurs in various plants
Junionone (juniper berry oil)
Menthone (geranium oil, peppermint oil) has a mint-like scent
Pinocarvone (eucalyptus oil) is the sexual hormone of the pine looper
Piperitone (eucalyptus oil)
Pulegone (pennyroyal oil): peppermint-like scent, irritates the skin
Thujone (thuja oil, sage oil): menthol-like scent
Verbenone (rosemary oil): mint-like scent belongs to the pheromones of the bark-beetle
Citral: is a mixture of citral A (geranial) and B (neral). Both have a lemon-like scent and are contained in lemon and lemongrass oil.
Citronellal (lemon oil, lime oil)
Safranal (saffron oil): is the main component of saffron.
As the list above illustrates, these compounds constitute the bulk of the active ingredients in almost all commonly used essential oils.
These aromatic compounds also contain the potential for therapeutic use as well, even beyond their traditional usage in aromatherapy. A number of terpene compounds have been determined to function as sedatives and anti-inflammatories.