Dear Sir;

basing on my short experience with the extraction of  "eugenol" from cloves, I think it depends on the targetted compound. If it is more abundant in one source than another one, it becomes obvious to deal with the highest loading one, of cource taking into account the ease of extraction, separation and purification. Regards

Marketability of essential oils is dictated by their odor and chemical profiles. Both major and minor components add to the odor or organoleptic profile of the essential oil. For some essential oils the market may demand a certain minimum percentage of a compound or compounds e.g. Cymbopogon martinii var. motia (palmarosa) essential oil should contain a minimum of 90% geraniol; Cymbopogon flexuosus (East Indian lemongrass) essential oil 75% citral; Cymbopogon winterianus (citronella) essential oil 35% citronellal and so on. The composition of a essential oil in terms of type of chemicals present and their percentage is affected by genetic, environment, management and other factors, therefore they keep changing in a plant material. Since the aroma profiles are specific to each essential oil, the presence of chemicals responsible for imparting that characteristic aroma is primary and their composition is secondary. However, in nature several chemotypes have been observed in many aromatic plants which may change this scenario. Ultimately it is the end use of the essential oil that dictates which one of the two factors is important for that use. 

Dear Saeid,

You have elaborated your question by giving an example of Rosa damascena essential oil. You wrote that, "we recognize 5 components as main components ( with low percentage), but in others we recognize components with most percentage as a main material."

I wish to share with you that

1. Indian Rose essential oil contained fragrant aroma constituents such as Citronellol, geraniol, nerol, linalool and phenylethanol as major constituents. Besides these, you may also observe other constituents including cis- and trans-rose oxide and some normal alkanes and alkene (due to the waxy appearance of the petals etc.)  in the GC profile with low proportions.

2.In some cases (as discussed by Dr BRR Rao in his answer), aromatic plants contained compounds with very high proportions in the respective essential oils. We can refer them as exclusive components rather than main components.

3. In my opinion, main component usually reflects proportion of a compound with good percentage in entire oil. But cannot be present in low percentage. However, they may be marker components with low percentage. If one has to discuss about the quality, certainly, composition can not be overlooked. Therefore, for better explanation, you may discuss about those five components in your next question.

Best of luck

Dr CS Chanotiya, CSIR-CIMAP, Lucknow, INDIA

Yes, for quality of essential oils  a good fragrance needs presence of eugenol, alkaloids, terpens, Citronellol, geraniol, nerol, linalool and phenylethanol, menthol, sterols, glycosides, acids, citrol or citral in a sizable proportion.