dc.description.abstract | Aromatic plants are commercially important and find wide use in food and pharmaceutical
industry, because of health benefits related with their antioxidant, antimicrobial, antiinflammatory, cardioprotective, cytotoxic, expectorant, anti-spasmodic and stimulant effects.
Most of phytochemicals are impossible to synthesize, therefore the best option is their extraction
from natural sources. Microwave-assisted extraction offers a rapid delivery of energy to a total
volume of solvent and solid plant material, improving the recovery of polyphenols. In the study,
wild thyme herb was evaluated as a source of polyphenols, which were extracted by the
application of microwaves instead of the traditional extraction techniques. The objective of the
present study was optimization of microwave-assisted extraction process through varying
irradiation time (5-180 s), temperature (60-200°C), particle size (0.3, 0.7 and 1.5 mm), solventto-solid ratio (10:1, 20:1, 30:1 and 40:1) and ethanol concentration in the extraction medium (0-
60%). Extraction efficiency was expressed via total polyphenol content (Folin-Ciocalteu method)
and antioxidant activity (ABTS radical scavenging method). The statistical analysis (one-way
ANOVA and Duncan's post-hoc test) has revealed that irradiation time above 15 s and particle
size have not shown statistically significant influence on polyphenol yield, while there were
significant differences between extracts obtained by various temperatures and solvent-to-solid
ratios. Although the highest polyphenol yield has achieved by using 50% of ethanol, there was
no statistically significant difference between ethanol concentration in the range from 30% to
50%. The highest polyphenol yield and antioxidant activity were achived in the extract with
particle size of 0.3 mm, 30:1 ratio and 50% ethanol, after 15 s, at 200°C (45.11 mg GAE/L and
27.22 µmol/L Trolox). According to the presented results, microwave-assisted extraction may be
used as an efficient and time saving alternative to traditional extraction techniques for extraction
of bioactive polyphenolic compounds from wild thyme. | sr |