Extraction solvent
Solvent extraction method is used to extract non-volatile essential oils
[44]. The plant materials are placed in a fresh solvent and is
removed non-volatile essential oils of plants. The solvent becomes more
enriched with the oil compounds of plants until extraction is complete,
followed by filtration. Finally, the filtrate is concentrated by solvent
evaporation and a thick residue called ”concentrate” is prepared. then
the concentrate mixed with alcohol to extract the oil compounds. The
alcohol absorbs oil compounds. Followed distillation of alcohol at low
temperatures, the concentrated compound is obtained, which is known as
the ”absolute” and used in perfumery. Solvents used in this method
should have a low boiling point, be free of odors and impurities, and
should also be inert to oil compositions [4, 45, 46]. Different
solvents are used in this method such as: acetone, hexane, petroleum
ether, methanol, or ethanol [47, 48, 49].
The most important advantage of this method is the appropriate and low
temperature (50 oC). Solvent extraction method has
disadvantages such as solvent toxicity in some cases, high solvent
consumption, flammability of solvents and the most important factor is
the solvent remaining in the final product [22].
Sara Lago [50] is reported
improved concentration of citrus essential oil by solvent extraction
with acetate ionic liquids. The results showed a great performance of
these acetate-based ionic liquids. Extraction essential oil of dried
sage (Salvia officinalis) using ethanol–water mixtures have been
studied by Nicola E.Durling [51]. This gave an extract including
6.9% rosmarinic acid (55% recovery), 10.6% carnosic compounds (75%
recovery) and 7.3% essential oil (42% recovery).