2.6.4 Chemical Characteristics of Volatile Oils
It has been observed that plethora of volatile oils are found to be more or less ‘complex mixtures’ essentially comprising of different class of chemical constituents. Therefore, they are found to vary widely in the chemical composition and vis-à-vis their therapeutic applications.
However, there are a few exceptions to the above observation wherein only one chemical entity is solely present in the naturally occurring volatile oil namely:
(a) Oil of Bitter Almond—contains benzaldehyde exclusively, and
(b) Oil of Winter Green—contains methyl salicylate exclusively
In fact, there are more than 500 different chemical compounds that have been duly isolated, purified and identified in volatile oils over the years with the advent of most sophisticated physicochemical methods of analysis, such as: UV-visible spectroscopy, IR-Spectroscopy, NMR – spectrometry, GC – analysis, HPLC–analysis, Mass spectrometry, X-ray diffraction analysis, optical rotary dispersion (ORD) analysis, HPTLC and the like.
The chemical constituents of volatile oils are recognized as ‘terpenes’ that may contain one or several isoprene units as shown below:
A few examples of some terpene hydrocarbons are summarized below:
Phenylpropanoids There is another major class of volatile oil constituents that invariably contains a C6 phenyl ring and an attached C3-propane side chain.
