Zaizhi Liu

An approach of ionic liquids/lithium salts based microwave irradiation pretreatment followed by ultrasound-microwave synergistic extraction for two coumarins preparation from Cortex fraxini

Ionic liquids/lithium salts solvent system was successfully introduced into the separation technique for the preparation of two coumarins (aesculin and aesculetin) from Cortex fraxini. Ionic liquids/lithium salts based microwave irradiation pretreatment followed by ultrasound-microwave synergy extraction (ILSMP-UMSE) procedure was developed and optimized for the sufficient extraction of these two analytes. Several variables which can potentially influence the extraction yields, including pretreatment time and temperature, [C4mim]Br concentration, LiAc content, ultrasound-microwave synergy extraction (UMSE) time, liquid-solid ratio, and UMSE power were optimized by Plackett-Burman design. Among seven variables, UMSE time, liquid-solid ratio, and UMSE power were the statistically significant variables and these three factors were further optimized by Box-Behnken design to predict optimal extraction conditions and find out operability ranges with maximum extraction yields. Under optimum operating conditions, ILSMP-UMSE showed higher extraction yields of two target compounds than those obtained by reference extraction solvents. Method validation studies also evidenced that ILSMP-UMSE is credible for the preparation of two coumarins from Cortex fraxini. This study is indicative of the proposed procedure that has huge application prospects for the preparation of natural products from plant materials.

Brönsted acidic ionic liquid based ultrasound-microwave synergistic extraction of pectin from pomelo peels

3-Methyl-1-(4-sulfonylbutyl) imidazolium hydrogensulfate, [HO3S(CH2)4mim]HSO4, was applied as an extractant in an ultrasound-microwave synergistic extraction approach to substitute conventional solvent for the extraction of pectin from the albedo part of pomelo peels. The analysis of variance (ANOVA) test and response surface method were employed for the optimization of the extraction conditions. A pectin yield of 328.64±4.19mg/g was achieved using the obtained optimal conditions, which was significantly higher than yields of conventional methods with reference solvents. Pectin samples extracted with [HO3S(CH2)4mim]HSO4 and hydrochloric acid solutions were tested by ANOVA and showed no significant differences in total carbohydrate content and degree of esterification; while galacturonic acid content was significantly different for the pectin from each extraction solvents. The differences revealed from images of atomic force microscopy and scanning electron microscope, Fourier transform infrared spectroscopy, and thermogravimetric analysis suggested the physiochemical properties of pectin could be affected by the extraction solvent. The [HO3S(CH2)4mim]HSO4 proved to be a promising alternative to conventional solvents and the proposed method is efficient for the extraction of pectin from the albedo of pomelo peels.

Process Optimization of Ultrasonic-Assisted Extraction of Arabinogalactan from Dihydroquercetin Extracted Residues by Response Surface Methodology and Evaluation of Its Antioxidant Activity

Ultrasound was used for the extraction of larch arabinogalactan from Larix 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.

A process to preserve valuable compounds and acquire essential oils from pomelo flavedo using a microwave irradiation treatment

A microwave pretreatment method was developed to preserve pectin, naringin, and limonin contents in pomelo flavedo to allow for longer storage times and subsequent extraction of pomelo essential oil. In terms of the essential oil, microwave pretreatment performed better than hydrodistillation with respect to extraction efficiency (1.88±0.06% in 24min versus 1.91±0.08% in 240min), oxygenation fraction (48.59±1.32% versus 29.63±1.02%), energy consumption (0.15kWh versus 1.54kWh), and environmental impact (123.20g CO2 versus 1232g CO2). Microwave-pretreated samples retained higher amounts of pectin, naringin, and limonin compared with non-pretreated samples. No obvious change in the degree of pectin esterification was observed. This study shows that the proposed process is a promising methodology for both preserving valuable compounds in pomelo flavedo during storage and acquiring essential oils.