Usage of microwave and ultrasound in the extraction of essential oils and phenolic compounds

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2011
İnce, Alev Emine
The objective of this study is to extract phenolic compounds from nettle and melissa by using microwave and ultrasound and to compare these methods with conventional extraction and maceration, respectively. Extraction of melissa essential oil was also studied. In extraction of phenolics, effects of extraction time (5-20 min for microwave; 5-30 min for ultrasound) and solid to solvent ratio (1:10, 1:20, 1:30 g/ml) on total phenolic content (TPC) were investigated for microwave and ultrasound extractions. Different powers were also studied for ultrasound extraction. In addition, effect of solvent type (water, ethanol, ethanol-water mixture at 50:50 v/v) was analyzed and water was found as better solvent. Optimum conditions for microwave extraction of phenolics were determined as 10 min and 1:30 solid to solvent ratio for nettle, and as 5 min and 1:30 solid to solvent ratio for melissa. TPC at these conditions for nettle and melissa extracts were 24.6 and 145.8 mg GAE/g dry material, respectively. Optimum conditions for ultrasound extraction was 30 min, 1:30 solid to solvent ratio, and 80% power for nettle and 20 min, 1:30 solid to solvent ratio, and 50% power for melissa. TPC at these conditions for nettle and melissa were 23.9 and 105.5 mg GAE/g dry material, respectively. Major phenolic acids were determined as naringenin in nettle and rosmarinic acid in melissa. Major aromatic compounds in melissa essential oil were found as limonene, citral, and caryophyllene oxide. Yields of essential oil obtained by microwave and hydrodistillation were 4.1 and 1.8 mg oil/g dry sample, respectively.
Citation Formats
A. E. İnce, “Usage of microwave and ultrasound in the extraction of essential oils and phenolic compounds,” M.S. - Master of Science, Middle East Technical University, 2011.