Extraction and Characterization of Essential oil from Thyme (Thymus Schimperi L.) Leaves by using Steam Distillation
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Date
2019-06
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Addis Ababa University
Abstract
Essential oils are very interesting natural plant products, and among other qualities they possess
various biological properties. This study has been carried out to extract the essential oil from the
leaves of thymus schimperi L. using steam distillation. Thyme (thymus schimperi L).is an
indigenous plant in Ethiopia and is locally called “Tosign’’ (in Amharic). It is among the
commonly occurring thymus species that distributed in different regions of Ethiopia. In this
research, thyme leaves were collected from debresina, Tarmaber Woreda. First, the leaf of thyme
was dried through partial sun drying. Then the dried thyme leaves were crushed in cross beater
mill with sieve size of 2mm and by cutting mill. The sample was sieved using a set of sieves sizes.
Next to this, the experimental work was carried out by steam distillation set up. A general factorial
design was employed to the extraction process using design expert 7.0 software and linear
regression model. This design helped to identify individual effects of extraction time, and particle
size, as parameter and their interaction in the entire extraction process. In the extraction
experiment, the minimum oil yield of 1.18% was obtained after the extraction time of 60 minutes
with particle size of 2 mm and maximum oil yield of 2.12 % was obtained at optimum extraction
time of 150 minutes with particle size of 0.5 mm. This shows that, increasing extraction time
(optimum of 150 minutes) and decreasing particle size increases the yield of oil. Characterization
of the oil was also carried out. Accordingly the yield was found with 1.54 refractive index value,
0.948
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specific gravity, and 0.42 degree optical rotation, 6.2 pH, 6.02 mpas dynamic viscosity,
1870C boiling, 101.512ml/g iodine value, 33.6 ml/g saponification value, 5.18 acid value, 28.42
ml/g ester value and 2.605% free fatty acid. The essential oil was analyzed by combined Gas
Chromatography and Mass Spectroscopy unit, and it was found to been reached in monoterpenes
alcohol and phenolic containing components. Among the major components from the GC-MS
analysis were thymol (63.20 %), p-Cymene (11.112%), Carvacrol (8.62%) and Linalool (2.41 %).
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Keywords
Composition, essential oil, extraction, GC-MS, thymus schimperi L., steam distillation, yield