Comparison of microwave and ultrasound-assisted extraction techniques for leaching of phenolic compounds from nettle

Abstract

In this study, extraction of phenolic compounds from nettle by microwave and ultrasound was studied. In both microwave and ultrasound-assisted extractions, effects of extraction time (5-20 min for microwave; 5-30 min for ultrasound) and solid to solvent ratio (1:10, 1:20, and 1:30 g/mL) on total phenolic content (TPC) were investigated. Effects of different powers (50 % and 80 %) were also studied for ultrasound-assisted extraction. In microwave-assisted extraction, the optimum TPC of the extracts (24.64±2.36 mg GAE/g dry material) was obtained in 10 min and at 1:30 solid to solvent ratio. For ultrasound-assisted extraction, the condition that gave the highest TPC (23.86±1.92 mg GAE/g dry material) was 30 min, 1:30 solid to solvent ratio, and 80 % power. Extracts obtained at the optimum conditions of microwave and ultrasound were compared in terms of TPC, antioxidant activity (AA) and concentration of phenolic acids with conventional extraction and maceration, respectively. Microwave reduced extraction time by 67 %. AA of extracts varied between 2.95±0.01 and 4.48±0.03 mg DPPH/g dry material among four methods. Major phenolic compounds were determined as naringenin and chlorogenic acid in nettle.

Enhancement of Chlorophyll a Production from Marine Spirulina maxima by an Optimized Ultrasonic Extraction Process

“…Ultrasonic extraction has most often been used to break down cell walls with high efficiency, but without additional heat that could deteriorate heat-labile bioactive substances in the biomass [7,[17][18][19] because a high frequency of ultrasonic vibration with high power input will make many cavitation bubbles in an extraction solvent, and the shock waves and liquid jets generated by breaking the bubbles near the cell walls could effectively destruct hard cell membranes in a shorter time [19,20]. However, there are still several hurdles to employing ultrasonic extraction processes in industrial applications such as relatively large equipment and more process controls as well as the difficulties of continuously combining with other processes such as fermentation and heating processes, etc.…”

Cymbopogon nardus Mediated Synthesis of Ag Nanoparticles for the Photocatalytic Degradation of 2,4-Dicholorophenoxyacetic Acid

“…The large number of the phenolic content may due to the simultaneous ultrasonic-hydrodistillation extraction method that provided much higher yield as compared to conventional aqueous extraction [12]. This results may be explained by the cavitation phenomena and mechanical mixing affect [12,36]. During the propagation of ultrasonic waves in ultrasoundassisted extraction, cavitation bubbles were generated at the surface of the solid matrix and causing a disruption of plant cell walls.…”

The effect of auxiliary energy on rhein, kaempferol and astragalin extraction fromCassia alata

“…MAE has shown to be more efficient for extraction of bioactive components than soxhlet, maceration and UAE because of short operating times [4]. MAE enhances the efficiency of extraction as compared to conventional extraction since microwaves interact with the polar molecules in the extraction media, heat is generated and the internal pressure of the solid material is increased [5,13]. Yet, other bioactive components such as rhein, kaempferol and astragalin are affected by microwave irradiation or high temperature, resulting in degradation [4].…”