Terpenes are among the main constituents of essential oils. However they may contain also other chemical classes, such as phenylpropanoids (i.e. eugenol, estragol, etc.) and aliphatic compounds. All of these classes may be formed by different functionalized structures, i.e. hydrocarbons, alcohols, aldehydes, ketones, esters, etc.
Terpenes are among the main constituents of essential oils. However they may contain also other chemical classes, such as phenylpropanoids (i.e. eugenol, estragol, etc.) and aliphatic compounds. All of these classes may be formed by different functionalized structures, i.e. hydrocarbons, alcohols, aldehydes, ketones, esters, etc.
Yes, I agree completely with Prof. Guido's answer. Ethers can be in the form of Furan derivatives.
Terpenoids, derived from Mevalonic acid pathway, are the major constituents of essential oils. Among the terpenoids monoterpenoids and sesquiterpenoids are common in essential oils, while diterpenoids are also distributed rarely. Phenyl propanoids, derived from Shikimic acid pathway, are the next major class of compounds. Aliphatic hydrocarbons are another class of volatile compounds in essential oils.
From GC-FID, you can easily get an idea, whether your sample is predominant with monoterpenoids or sesquiterpenoids; monoterpenoids were eluted in the first half of the chromatogram, while the less volatile sesquiterpenoids were eluted in the last half of the chromatographic run. from GC-MS the monoterpenoids can easily be identified based on the molecular ion peak at 136 (C10H16) or nearby, while sesquiterpenoids give 204 (C15H24) or nearby molecular ion peaks. Further the monoterpenoids and sesquiterpenoids possess characteristic fragmentation patterns, by which one can easly distinguish them.
Essential oils are complex mixtures, constituted by terpenoid hydrocarbons, oxygenated terpenes and sesquiterpenes. They originate from the plant secondary metabolism and are responsible for their characteristic aroma.
Or it can be said that, "Essentials oils are composed of Terpenes and their oxygenated derivatives".
The term ‘terpene’ was given to the compounds isolated from terpentine, a volatile liquid isolated from pine trees. The simpler mono and sesqui terpenes are chief constituent of the essential oils obtained from sap and tissues of certain plant and trees. The di and tri terpenoids are not steam volatile. They are obtained from plant and tree gums and resins. Tertraterpenoids form a separate group of compounds called ‘Carotenoids’
The term ‘terpene’ was originally employed to describe a mixture of isomeric hydrocarbons of the molecular formula C10H16 occurring in the essential oils obtained from sap and tissue of plants, and trees. But there is a tendency to use more general term ‘terpenoids’ which include hydrocarbons and their oxygenated derivatives.
By the modern definition: “Terpenoids are the hydrocarbons of plant origin of the general formula (C5H8)n as well as their oxygenated, hydrogenated and dehydrogenated derivatives.”
Each essential oil is made up of numerous different organic molecules. What gives every essential oil its uniqueness is not just one of its constituents, but the whole, delicate and complex admixture. The individual perfume of each oil depends on this balance; the therapeutic value of each oil depends on it too. It is the number of constituents of an oil which make it almost impossible to reproduce exactly with synthetic ingredients. The reaction between these constituents and their component molecules gives the oil its therapeutic value, which is why man-made imitations never have the same power to heal as their natural counterparts.
From the chemical point of view, the essential oil composition frequently changes in different parts of the plant. Quite often, between the different organs of the plant, phytochemical polymorphism can be produced.
GC is an effective solution for essential oil analysis.
Essential oils consist to mono, sesqui and acro-terpenes, its a secondary metabolites may convert from type to type. it depends on molecular wight
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