Abstract
Ultrasound was used for the extraction of larch arabinogalactan fromLarix gmelinii. The optimal conditions for ultrasound extraction were determined by response surface methodology. Specifically, the Box-Behnken design was employed to evaluate the effects of three independent variables: ultrasound time, temperature, and liquid-solid ratio. The highest arabinogalactan yield (11.18%) was obtained under the optimal extraction condition (extraction temperature 41.5°C, extraction time 24.3 min, and liquid-solid ratio 40 mL/g). In addition, the antioxidant activity of arabinogalactan that was extracted from dihydroquercetin extraction residues exhibited a moderate and concentration-dependent hydroxyl radical-scavenging capacity, ferric-reducing power, and reducing power. The wood material was characterized before and after processing by scanning electron microscopy and Fourier-transform infrared spectroscopy.
Highlights
Larix gmelinii is a medium-sized, deciduous coniferous tree primarily distributed in Greater and Lesser Khingan of China, north Sakhalin, and east Siberia [1]
When the liquid-solid ratio was fixed at 40 mL/g, the arabinogalactan yield decreased with increasing extraction temperatures over the range 40–60∘C
The Ultrasound-assisted extraction (UAE) conditions were optimized in detail and were found to be an extraction temperature of 41.5∘C, an extraction time of 24.3 min, and a liquid-solid ratio of 40
Summary
Larix gmelinii is a medium-sized, deciduous coniferous tree primarily distributed in Greater and Lesser Khingan of China, north Sakhalin, and east Siberia [1]. It has been reported that it contains valuable bioflavonoids such as dihydroquercetin (taxifolin) [2] and polymeric procyanidins [3] These bioactive components in L. gmelinii residues could be extracted for an economical utilization. In the conventional process of dihydroquercetin production, ethanol has been used as the extraction solvent, and large amounts of remainder residues have been produced and discarded [4–6]. The preliminary experiments undertaken in the present study have shown that the extract residues in the production of dihydroquercetin contain large amounts of arabinogalactan. Ultrasound-assisted extraction (UAE) is one way to solve this problem [21–23] It offers high reproducibility, short extraction times, simple manipulation, low solvent consumption, low temperatures, and low energy input [24–26]. The objective here is to develop an effective and environmentally friendly UAE approach for the extraction of the arabinogalactan from the extract residues in the production of dihydroquercetin. The antioxidant activities of the extracted arabinogalactan were evaluated by its hydroxyl radical-scavenging capacity, its ferric-reducing antioxidant power, and its reducing power
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