Abstract Schisandra chinensis is a plant with high medicinal value, which contains many medicinal ingredients, including 5‐hydroxymethylfurfural. In the present study, an efficient method based on high‐speed counter‐current chromatography was established for the preparation of 5‐hydroxymethylfurfural from Schisandra chinensis . Petroleum ether–ethyl acetate–methanol–water (2:5:2:5, v/v) was selected as the solvent system for high‐speed counter‐current chromatography. In order to improve the yield of single separation, the sample size was continuously optimized and improved. The results showed that 1,250 mg was the most suitable sample size, and 41 mg of the target compound with 97% purity was obtained in a single run. To further improve the yield, consecutive high‐speed counter‐current chromatography was introduced and compared with the results of a high‐speed counter‐current chromatography single run. The results showed that although the purity was reduced to 92%, 430 mg of the target compound was obtained from 12.5 g of ethanol extract within 670 min after 10 consecutive injections. This indicated that consecutive separation not only increased the yield of the target compound, but also saved the separation time and greatly improved the separation efficiency of high‐speed counter‐current chromatography.
Abstract Brookite TiO 2 is a metastable crystalline phase, which is difficult to prepare manually. In this study, brookite TiO 2 with controllable morphology was synthesized by a simple hydrothermal method. The prepared brookite TiO 2 was a complete rice‐like granular particle with a smooth surface and sharp edges at the tip of both ends. And the diameter of an individual brookite TiO 2 was approximately 200 nm. Then, to improve the photocatalytic degradation performance of brookite TiO 2 , we prepared Bi 2 O 3 /brookite TiO 2 nanocomposites. After Bi 2 O 3 composite, the crystalline phase of brookite TiO 2 did not change, and still maintained high purity and crystallinity. The Bi 2 O 3 nanoparticles were dispersed on the surface of brookite TiO 2 , forming heterogeneous structures in close contact. The Bi 2 O 3 /brookite TiO 2 nanocomposite exhibited a significantly higher degradation rate of ofloxacin (20 mg L −1 ) under visible light (300 W Xenon lamp, λ ≥ 400 nm) compared to pure brookite TiO 2 . The photocatalytic activity of 5 mol% Bi 2 O 3 /brookite TiO 2 was the best, the degradation rate of OFX reached 90.7%. The enhancement of photocatalytic activity of Bi 2 O 3 /brookite TiO 2 nanocomposites was attributed to the formation of Bi 2 O 3 /brookite TiO 2 heterojunction, which accelerated the photogenerated charge‐hole separation. This study provided theoretical support for efficient photocatalytic degradation of pollutants.
Coprinus comatus is an edible mushroom and its fermented product possesses antioxidant activity. In this study, to further enhance the antioxidant activity and improve the reusability of the strain, calcium alginate hydrogel was used as the carrier for embedding and immobilizing Coprinus comatus. The effects of CaCl2 concentration, sodium alginate concentration, microsphere diameter, and the amount of magnetic particle on the antioxidant activity of fermented products were investigated. The results showed that the magnetic immobilized microsphere prepared by 2.50% CaCl2, 2.00% sodium alginate and 0.50% Fe3O4 had the best fermentation antioxidant activity (EC50 was 0.43 ± 0.01 mg/mL) when the diameter was 5 mm, which increased by 24.56% compared to the initial activity. Besides, the microsphere showed strong reusability, the antioxidant activity was still better than the free strain after being used five times. This study not only enhanced the antioxidant activity of Coprinus comatus fermented product through immobilization, but also provided an effective method for microbial fermentation.
Ellagic acid is one of the most representative natural antioxidants, and is rich in pomegranate peel. In this study, a consecutive countercurrent chromatographic (CCC) separation method was established to improve the preparative efficiency of ellagic acid from pomegranate peel. By optimizing the solvent system, sample size and flow rate, 280 mg of ellagic acid was obtained from 5 g of crude sample from pomegranate peel by CCC after six consecutive injections. Moreover, the values of EC50 for ellagic acid in scavenging ABTS·+ and DPPH· were 4.59 ± 0.07 and 10.54 ± 0.07 μg/ml, respectively, indicating a strong antioxidant activity. This study not only established a high-throughput method for the preparation of ellagic acid, but also provided a successful example for the development of and research on other natural antioxidants.
Coprinus comatus is an edible and medicinal fungus. In this study, the antioxidant activity of the fermentation product of C. comatus was investigated through optimization of fermentation process. The results indicated that the fermentation product of C. comatus had obvious scavenging ability for 2,2'-Azino-bis(3-ethylbenzothiazoline)-6-sulphonic acid (ABTS) free radical. The EC50 of the n-butanol extract from the fermentation product on ABTS·+ was 0.65 ± 0.02 mg/mL. On this basis, the liquid fermentation conditions of C. comatus were optimized through single factor and response surface optimization experiments according to the scavenging ability of ABTS·+ to improve the antioxidant capacity of the fermentation product. The results showed that when the 14% of C. comatus was fermented in a culture medium with a C/N ratio of 48:1 for 6 days, the ABTS·+ scavenging ability was the strongest, and the EC50 of n-butanol extract was 0.57 ± 0.01 mg/mL, which was 12.31% higher than the initial activity. This study laid the foundation for the development of C. comatus.
Robinia pseudoacacia flowers have attracted much attention because of numerous bioactivities. In this study, its extract showed the potential scavenging ability for 2,2′‐azinobis‐(3‐ethylbenzthiazoline‐6‐sulphonate) and 1,1‐diphenyl‐2‐picrylhydrazyl free radicals. Under the guidance of antioxidant activity, the antioxidant extract was enriched by liquid‐liquid extraction. The partition coefficients of the two main components in antioxidant extracts differed greatly, so in this study, elution‐extrusion counter‐current chromatography with the solvent system of n ‐hexane‐ethyl acetate‐methanol‐water (2.5:5:2.5:5, v/v) was used to enhance the separation efficiency, and the two main components were successfully obtained. Among them, kaempferol showed strong antioxidant activity, which can be responsible for the activity of the extract. In order to deeply understand the antioxidant mechanism of kaempferol, the thermodynamics, frontier molecular orbital, and kinetics of scavenging free radicals were investigated by density functional theory. The results showed that 4′‐OH in kaempferol was the most active group, which can scavenge free radicals by hydrogen atom transfer in non‐polar solvents and activate 3‐OH to generate double hydrogen atom transfer in the gas phase. But in polar solvents, it was more inclined to clear radicals through single electron transfer and proton transfer. The kinetic result showed that kaempferol needed 9.17 kcal/mol of activation energy to scavenge free radicals.
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