Effects of microwave and ultrasonic extraction methods on total phenolic content of nettle (Urtica diocia)

Ince, Alev Emine
Şahin, Serpil
Sumnu, Gulum
Abstract. Effects of different extraction methods at different conditions on total phenolic content (TPC) of nettle (Urtica diocia) were investigated. Water was used as solvent. TPC analysis was performed according to Folin-Ciocalteu method. In microwave extraction, heating was achieved using microwaves at 407W power level. Effects was obtained as 1:30 solid-to-solvent ratio for 10min. Extraction was also performed conventionally at 1:30 solid-to-solvent ratio for 30min for comparison. There was no significant difference between microwave and conventional extractions with respect to TPC but extraction time was reduced by about 67% in of different solid-to-solvent ratios (1:10, 1:20 and 1:30g/ml) and times (5, 10, 15, and 20min) were studied. The best extraction condition microwave extraction. Extractions using ultrasonic probe were performed in two different power levels (50% and 80% power) at 50% pulser mode and at 40±5°C temperature. Maximum power of ultrasound was 300W. Different solid-to-solvent ratios (1:10, 1:20 and 1:30) and time levels (5, 10, 20, and 30min) were experienced. Solid-to-solvent ratio of 1:30, 30min and 80% power were determined as optimum condition in ultrasonic extraction. Extraction was also performed with maceration using 1:30 solid-tosolvent ratio at 40°C for 24h for comparison. There was no significant difference between ultrasonic extraction and maceration with respect to TPC. TPC of nettle by different extraction methods changed in the range of 19.7- 28.8 mg GAE (Gallic Acid Equivalent)/g dry material. TPC of extracts obtained by microwaves and ultrasound were not significantly different from each other but extraction time was reduced significantly in microwave extraction