Extraction of Volatile Oils

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Chapter: Pharmacognosy and Phytochemistry : Drugs Containing Volatile Oils

Volatile oils are prepared by means of several techniques and those techniques are discussed here


EXTRACTION OF VOLATILE OILS

 

 

Volatile oils are prepared by means of several techniques and those techniques are discussed below:

 

Extraction by Distillation

 

The distillation is carried out either by water or steam. The volatile oils from fresh materials are separated by hydrodistillation, and volatile oils from air dried parts are separated by steam distillation. However it is better to use fresh materials in either case.

 

Extraction by Scarification

 

This method is used for the preparation of oil of lemon, oil of orange, and oil of bergamot. These oils are found in large oil glands just below the surface in the peel of the fruit. The two principal methods of scarification are the sponge and the ecuelle method.

 

a. Sponge Process: In this process the contents of the fruit are removed after making longitudinal or transverse cut, and the peel is been immersed in water for a short period of time. Then it is ready for expression. The operator takes a sponge in one hand and with the other presses the softener peel against the sponge, so that the oil glands burst open and the sponge absorbs the exuded oil, which is transferred to a collecting vessel. The turbid liquid consisting of oil and water is allowed to stand for a short time, whereupon the oil separates from water and is collected. The whole of the above process is carried out in cool, darkened rooms to minimize the harmful effects of heat and light on the oil.

 

b. Ecuelle Process: In this process, the rinds are ruptured mechanically using numerous pointed projections with a rotary movement and the oil is collected.

 

Extraction by Non-Volatile Solvent

 

A nonvolatile solvent, for example, a fine quality of either lard or olive oil, is used in this process. After saturation with the floral oil the lard or olive oil is sometimes used as a flavouring base for the preparation of pomades, brilliantine, etc., or converted to a triple extract. In the latter instance the lard or oil is agitated with two or three successive portions of alcohol, which dissolve the odorous substances. The mixed alcoholic solutions so obtained constitute the ‘triple extract’ of commerce.

 

There are three chief methods that come under this; they are enfleurage, maceration and a spraying process.


1.     Enfleurage: In this a fatty layer is prepared using lard and the flower petals are spreaded over it, after the imbibitions is over the fatty layer is replaced with fresh petals. After the saturation of fatty layer the odorous principles are removed by treating with alcohol and a triple extract then prepared. When oil is used as a solvent the flowers are placed on an oil-soaked cloth supported by a metal grid enclosed in a frame. Fresh flowers are added as required, and finally the oil is expressed from the cloths. It may then be used as perfumed oil, or extracted with alcohol to produce a triple extract.

 

2.     Maceration: This is also used to extract the volatile matters of flowers. The lard or oil is heated over a water bath, a charge of flowers added and the mixture stirred continuously for some time. The exhausted flowers are removed, pressed, the expressed fluid returned to the hot fat, fresh flowers, added and the process continued until defined weights of flowers and solvent have been used. Again, a triple extract is prepared by extracting the perfumed lard or oil with alcohol.

 

3.     Spraying: In this process a current of warm air is sprayed through a column of the flowers. Then oil or melted fat is sprayed over this oil-laden air which absorbs and dissolves most of the perfume, the collected oil or fat is then extracted with alcohol as described above.


Extraction by Volatile Solvent

 

In this the flowers are extracted by using the solvent light petroleum and the latter is distilled off at a low temperature, leaving behind the volatile oil.

 

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