Extraction And Characterization Of Essential Oil From Thyme (thymus Schimperi L.) Leaves By Using Steam Distillation

Essential oils are very interesting natural plant products, and among other qualities they possessrnvarious biological properties. This study has been carried out to extract the essential oil from thernleaves of thymus schimperi L. using steam distillation. Thyme (thymus schimperi L).is anrnindigenous plant in Ethiopia and is locally called “Tosign’’ (in Amharic). It is among therncommonly occurring thymus species that distributed in different regions of Ethiopia. In thisrnresearch, thyme leaves were collected from debresina, Tarmaber Woreda. First, the leaf of thymernwas dried through partial sun drying. Then the dried thyme leaves were crushed in cross beaterrnmill with sieve size of 2mm and by cutting mill. The sample was sieved using a set of sieves sizes.rnNext to this, the experimental work was carried out by steam distillation set up. A general factorialrndesign was employed to the extraction process using design expert 7.0 software and linearrnregression model. This design helped to identify individual effects of extraction time, and particlernsize, as parameter and their interaction in the entire extraction process. In the extractionrnexperiment, the minimum oil yield of 1.18% was obtained after the extraction time of 60 minutesrnwith particle size of 2 mm and maximum oil yield of 2.12 % was obtained at optimum extractionrntime of 150 minutes with particle size of 0.5 mm. This shows that, increasing extraction timern(optimum of 150 minutes) and decreasing particle size increases the yield of oil. Characterizationrnof the oil was also carried out. Accordingly the yield was found with 1.54 refractive index value,rn0.948rn��rn����3rn specific gravity, and 0.42 degree optical rotation, 6.2 pH, 6.02 mpas dynamic viscosity,rn1870C boiling, 101.512ml/g iodine value, 33.6 ml/g saponification value, 5.18 acid value, 28.42rnml/g ester value and 2.605% free fatty acid. The essential oil was analyzed by combined GasrnChromatography and Mass Spectroscopy unit, and it was found to been reached in monoterpenesrnalcohol and phenolic containing components. Among the major components from the GC-MSrnanalysis were thymol (63.20 %), p-Cymene (11.112%), Carvacrol (8.62%) and Linalool (2.41 %).

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