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Abstract
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The genus Stachys is a member of the Lamiaceae family. These are important medicinal
plants which grow all over the world and are known for their flavoring and therapeutic
effects and Stachys lavandulifolia is an endemic species of Iran. To acquire high-quality
essential oil (EO), drying technique was implemented which is an essential part of this
process. The present study designed to evaluate the influences of different drying
techniques (fresh sample, shade, sunlight, freeze-drying,
microwave, and oven-drying
(40, 60, and 80°C) on EO yield and composition of S. lavandulifolia. The results indicated
that the maximum EO yield was obtained by the shade-drying
method. The
main compounds found in the fresh samples were spathulenol, myrcene, β-pinene,
δ-cadinene,
and α-muurolol,
while spathulenol, cyrene, δ-cadinene,
p-cymene,
decane,
α-terpinene,
β-pinene,
and intermedeol were found to be the dominant compounds
in the dry samples. Drying techniques were found to have a significant impact on the
values of the main compositions, for example, monoterpene hydrocarbons such as
α-pinene,
β-pinene,
myrcene, and β-phellandrene
were significantly reduced by microwave
drying, oven-drying
(40, 60, and 80°C), and sunlight-drying
methods. Drying
techniques increased the antioxidant activity of S. lavandulifolia EOs especially those
acquired by freeze-drying
with the half-maximal
inhibitory concentration (IC50) values
101.8 ± 0.8 mg/ml in DPPH assay and 315.2 ± 2.1 mg/ml in decreasing power
assay. As a result, shade-,
sun-,
and oven-drying
(40°C) were found to be the most
important techniques for attaining maximum yields of EO.
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