Extraction and Use of Terpenoids

Terpenoids are also put to uses for which their physical or chemical properties suit them but which are not the uses for which nature originally intended them. Rubber is a polymer of isoprene which is produced in the rubber tree as a defensive secretion but is widely used by humans because of its elastic properties. Turpentine has a long history of use as a solvent, particularly for paints and, similarly, lac resin as varnish. Nowadays, turpentine is also used as a feedstock for the synthesis of other materials of commercial interest, in addition to a wide variety of fragrance ingredients. 

The methods used to extract perfume ingredients from their natural sources have changed over time as technology in general has advanced. However, both old and new methods fall into four basic classes tapping, expression, distillation and solvent extraction. 

Many plants, particularly trees, exude resins when their bark is damaged. Deliberate damage and subsequent collection of the resin is known as tapping. This method is used to collect latex for rubber production and for gum turpentine. It is also used to produce frankincense (also known as olibanum), myrrh and other similar fragrance materials although in these cases there is usually further processing of the resin after collection. 

When oils are forced out of the natural source by physical pressure, the process is referred to as expression and the product is called an expressed oil. If you squeeze a piece of orange peel, you will see the oil bearing glands burst and eject a fine spray of orange oil. Many commercially available citrus oils, bergamot in particular, are prepared in this way. 

Hydrodiffusion is a relatively new technique. It is essentially a form of steam distillation. However, it is steam distillation carried out upside down since the steam is introduced at the top of the pot and the water and oil taken off as liquids at the bottom. The plant materials diffuse through the cell membranes into the steam and are carried to the bottom of the still by the descending flow of condensate. This technique therefore saves energy because it is not necessary to vaporise the oil. 

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