Solvent Extraction
A typical solvent like ethanol, methanol, hexane, petroleum ether, or acetone has been executed by this method to extract delicate or fragile flower materials that cannot be obtained by the application of Supplied steam or heat [2]. Usually, a sample plant is mixed with solvents to be separated by gently heating of mixture, and the solvent’s filtration and evaporation pursue the procedure. The filtrate includes resinoid (a resin), or a mixture essential oil, fragrance and wax. Alcohol is mixed with the mixture of the filtrate to dissolve the essential oil into the alcohol. Which is then separated by distillation at reduced temperature. During the process of distillation, the fragrance is absorbed by alcohol and is evaporated, whereas the absolute aromatic oil leftovers in the residue pot. Comparing to other means, this techniques is more complicated for extraction of essential oils, and accordingly, more expensive and time-consuming [29].
In another research, the researcher evaluated the antioxidant action of Ptychotis verticillata by solvent extraction procedure for the extraction of essential oils. It was revealed the existence of phenolic compounds (48%) and comprised thymol and carvacol (3.4% and 44.6%) respectively as the chief constituents [30].
In other researches, the essential oils were obtained from TPS (Thymus praecox subsp. Skorpilii var. Skorpilii), and its antioxidant potential and chemical components were evaluated by combining the plant extract with numerous solvents like water, methanol and ethanol. This extracts revealed considerable free-radical scavenging potential with o-cymene and thymol (13.66% and 40.31% respectively). These findings also revealed that the extraction procedure applying water as the solvent provides maximum flavonoids and phenolics contrasted to other solvent types [31].