The production of glucuronic acid (GA) directly from actual biomass via chemocatalysis is of great significance to the effective valorisation of biomass for a sustainable future. Herein, we have developed a one-step strategy for the conversion of cellulose in corncob residue into GA with the cooperation of Au/CeO2 and maleic acid, achieving a 60.3% yield. Experimental and density functional theory (DFT) results show that maleic acid is effective in the fractionation of cellulose from corncob residue and the depolymerisation of cellulose fragments to glucose, on account of the good capacity for proton migration. Au/CeO2 is responsible for the selective oxidation of glucose to GA, in which the formation of glucaric acid is restrained, due to the weak capacity of Au/CeO2 on the proton transfer without the occurrence of the ring-opening reaction of glucose. Therefore, the relay catalysis of Au/CeO2 and maleic acid enables the production of GA via the complex cascade reactions. This work may provide insight regarding the conversion of actual biomass to targeted products.

The accumulation of β-amyloid (Aβ) in the brain plays an important role in the pathogenesis of Alzheimer’s disease (AD). The lack of estrogen is one of the risk factors for AD. Quercetin is a phytoestrogen with a chemical structure similar to that of estrogen. However, the mechanism by which quercetin prevents AD is unclear. PC12 cells were cultured with Aβ25–35 for 24 h. Then the cells were further treated with 17β-estradiol, genistein, and quercetin for another 24 h, respectively. Next, ICI182780 and U0126 were used to study the mechanisms of estrogen-like neuroprotection. Methyl thiazolyl tetrazolium (MTT) assay was performed to detect cell survival. The protein expression was analyzed by immunofluorescence and western blot. The survival of PC12 cells induced by Aβ25–35 was increased by quercetin. The levels of estrogen receptor α (ERα) and p-extracellular signal-regulated kinase (ERK)1/2 were improved by quercetin, but not those of ERβ. On the contrary, Bcl-2/Bax was increased and the expression of Caspase-3 was decreased. When the cell was pretreated with ICI182780, the p-ERK1/2 and Bcl-2/Bax ratio was decreased, but Caspase-3 expression was increased. In addition, pretreatment with U0126 would reduce Bcl-2/Bax ratio and increase Caspase-3 protein expression. Conclusively, quercetin plays a neuroprotective role through the ER pathway and the mitogen-activated protein kinase (MAPK) pathway. The MAPK signaling pathways could also be activated by quercetin via the mediation of ERα.

Gliadin was reacted with citric acid under weak acidic and weak alkaline conditions in both wet and dry states and the reaction mechanism was studied. The low morphological stability in an aqueous environment and inferior mechanical properties have restricted the applications of plant proteins, although these materials possess a unique structure, biocompatibility and biodegradability. Carboxylic acids such as citric acid are inexpensive and nontoxic chemicals and are preferred for crosslinking proteins and cellulose to improve the desired properties of the materials. In this study, gliadin was chosen as a model of plant proteins because it contained relatively more amine side groups that can react with a carboxylic acid crosslinker than other plant proteins, e.g. zein and soy proteins. In order to avoid using toxic chemicals and experiencing strength loss and/or yellowing of the crosslinked materials, alkaline catalyzed crosslinking of gliadin powders in aqueous citric acid solutions at low temperatures was employed. However, previous research only provided limited evidences, such as improvement in mechanical properties to support the presence of the acylation reaction. To explore the reaction mechanism, titration method was used to investigate the influences of pH, citric acid concentration and reaction temperature on both carboxyl and amine group changes during the reaction. The kinetic parameters of both reaction states have been obtained at different temperatures. Additionally, to further improve the crosslinking degree, a dry state crosslinking of gliadin films with citric acid was also studied. A relationship between the mechanical properties and the crosslinking degree has also been developed.

Alkali-extracted tea polysaccharide conjugates, termed TPC-A, are obtained from the residue derived from tea after water extraction. Oil-in-water emulsions stabilized by different concentrations of TPC-A (0.5 wt%, 1.0 wt %, 1.5 wt %, 2.0 wt %, and 3.0 wt%) were prepared using medium chain triglycerides (MCT). The optimal concentrations of TPC-A were 2.0 wt % and 3.0 wt %. We investigated the effects of the storage time of 10 days, pH 2.0-10.0, and metal ions (Na+ and Ca2+ ) on the emulsion stabilized using 2.0 wt % TPC-A at 25 degrees C. During the 10-day storage period, the mean particle diameter (MPD) (d(32)) of the emulsion stabilized using 2.0 wt % TPC-A slightly increased from 0.31 mu m to 0.37 mu m, and the absolute value of the zeta potential increased from 44.9 mV to 41.4 mV. Under neutral or alkaline conditions, the emulsion stabilized using TPC-A had the MPD (d(32)) of less than 0.30 mu m and the absolute value of the zeta potential ranging from 40.52 to 41.53 mV. The MPD (d(32) ) of the emulsion in different Na+ concentrations from 0 mmol/L to 500 mmol/L, increased from 0.30 mu m to 2.80 mu m, and their absolute value of zeta potential decreased from 41.0 mV to 37.7 mV. The emulsion stabilized using TPC-A had a favorable protective effect on EGCG and EGC, and the retention rates of EGCG and EGC during the 10 days were 7 and 6 times higher than those without TPC-A emulsion protection, respectively. TPC-A extracted from tea residue, which is abundantly available and cheap, can be used as a natural emulsifier, in order to develop a milky food or beverage products with excellent health benefits.

Dihydromyricetin is a natural flavonoid and principal component of the Chinese herbal tea, Ampelopsis grossedentata, with numerous health-promoting bioactivities. Response surface methodology (RSM) was employed to optimize the extraction of dihydromyricetin from Ampelopsis grossedentata leaves using dynamic microwave assisted multi-stage countercurrent extraction. The influence of temperature, pH, time and solvent/material ratio on the yield of extraction was investigated. It was found that the extraction data were sufficiently fitted into a second-order polynomial model (R-2 = 0.9992). The extraction parameters of temperature, pH and solvent/material ratio, the quadrics of time, temperature and pH, and the interaction between each two of the four extraction parameters had a significant effect on the yield. The optimal conditions for extracting dihydromyricetin were predicted to be: temperature, 96.8 degrees C; time, 8.8 min; solvent/material ratio, 26.4/1 and pH, 5.3. Under those conditions, the predicted yield was 92.3% of dihydromyricetin in the leaves.

Dihydromyricetin is the principle component of the Chinese herbal tea Teng-cha and a promising ingredient for functional food and nutraceuticals, but its low solubility limits its application potentials. This study explored enzymatic acylation of dihydromyricetin to improve its solubility in lipid systems. Acylation was achieved with several lipases with the synthesis of a major (>86%) product and a minor product. Isolation and purification of the products by preparative HPLC followed by LC-MS, (13)C NMR, (1)H NMR and 2 D-HSQC NMR analyses showed that the major product was a dihydromyricetin monoester with the acylation site at the 3-OH group of C ring. Quantum chemical calculations revealed that the 3-OH had the lowest antioxidant activity, and therefore acylation at this site was expected to have minimum impact on the antioxidant activity. Several factors, including solvent, acyl donor, enzyme origin, molar ratio of substrates and reaction temperature and time, exhibited significant effects on the initial rate, conversion yield and regioselectivity of the reaction. Acylation occurred only with vinyl acetate as the acyl donor, and highest conversion yields were achieved with immobilized Penicillium expansum lipase and Novozyme 435 with DMSO and acetonitrile being the best solvents. In general, the acylation results were found to be superior to previous reports on acylation of aglycone flavonoids with respects to conversion yield and regioselectivity.

在单因素试验的基础上,对乙醇浓度、提取时间、液固比和提取温度4因素进行Box-Behnken组合试验设计并通过响应面分析,优化黑三棱中黄酮类化合物的提取工艺.结果表明:提取黑三棱中黄酮类化合物的最佳工艺参数为乙醇体积分数66％、提取时间61min、液固比40:1,提取温度81℃.在此条件下,黄酮类化合物的实际提取率为33.79mg/g,与预测值33.77mg/g基本一致.在4个因素中,乙醇体积分数对提取率影响最大,其次是提取温度,而提取时间、液料比对黄酮类化合物提取率影响较小,并且提取时间和提取温度的交互作用对黄酮提取率有较小影响,其他的因素间无交互作用.

The optimal ultrasonic extraction technology and antioxidant activities of flavonoids from Polygonum perfoliatum L. and Sonchus oleraceus L. were studied and compared. The optimal flavonoids extraction conditions were acquired with single factor experiment and orthogonal experiment. The optimal extraction condition was solid-liquid ratio 1:50, ethanol 65%vol, and ultrasonic extraction time 50min. Under this condition, the flavonoids yield of P. perfoliatum and S. oleraceus were 70.77mg/g and 18.54mg/g, respectively. The inhibition rate of two kinds of flavonoides on·OH were different in different system, the scavenging activity of flavonoids from S. oleraceus was higher than flavoniods from P. perfoliatum, and they were 7.9 and 1.35 times than that of rutin and Vc in salicylic acid system, respectively. While in phenanthroline system, the inhibition rate of flavonoides from P. perfoliatum was higher than flavoniods from S. oleraceus, and the inhibition activity on·OH were approximately 2.5 times than rutin and VC.

Pomegranate peel is the main byproduct of pomegranate juice manufacture and is rich in phenolic acids, but most of which exist in the bound form with low bioavailability. A simple, low-cost procedure for releasing phenolic acids from pomegranate peel was developed, which uses a mild alkaline treatment of the peel at room temperature. Results showed that when the peel was treated with 0.5mM NaOH for 3h, the concentration of ellagic acid, one of the two main phenolic acids present, almost doubled, while gallic acid, the other main phenolic, which was not found in the free form, was released at a concentration almost twice as high as that of ellagic acid. With the release of the two phenolic acids, the extract of the pomegranate peel showed remarkable increases in their antioxidant activity measured by three different essays. However, more severe alkaline treatment either by extending the hydrolysis time to 6h or longer, or by using a higher concentration of NaOH (2mM), resulted in decreases in the phenolic acids, possibly as a result of alkaline-induced degradation, with corresponding decreases in antioxidant activities. These results showed that the mild alkaline treatment process could be a low cost but efficient method that can be used to increase the level of phenolic acids and hence the potential value of pomegranate peel extract.PRACTICAL APPLICATIONSPomegranate peel is the main byproduct of pomegranate juice manufacture and is rich in phenolic acids, but most of which exist in the bound form with low bioavailability. A simple, low-cost procedure for releasing phenolic acids from pomegranate peel was introduced in this article, which uses a mild alkaline treatment of the peel at room temperature. The method was practical and the extract could be used as antioxidant and active supplement.

The formation of supramolecular inclusion complexes between luteolin and five cyclodextrins namely β-cyclodextrin (β-CD), methyl-β-cyclodextrin (M-β-CD), hydroxyethyl-β-cyclodextrin (HE-β-CD), hydroxypropyl-β-cyclodextrin (HP-β-CD) and glucosyl-β-cyclodextrin (G-β-CD) was investigated. Results from phase-solubility studies showed that luteolin formed 1:1 stoichiometric inclusion complexes with these cyclodextrins with the G-β-CD complex displaying the greatest stability constant. The supramolecular structure of the luteolin/G-β-CD complex was investigated by ultraviolet–visible spectroscopy (UV), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and X-ray diffractometry (XRD). Results showed clearly the formation of a supramolecular complex in which the guest molecule, luteolin, was entrapped inside the cavity of the host, G-β-CD. The close association between luteolin and G-β-CD resulted in changes in some of the characteristic spectral, phase transitional and morphological properties of luteolin. Furthermore, molecular docking study showed that the complex was formed with the B ring of luteolin inserted into the cavity of G-β-CD.

The inclusion complexation of (2-hydroxypropyl)-cyclodextrins with flavanones was investigated by phase solubility measurements, as well as thermodynamic and quantum chemical methods. Inclusion complexes were formed between (2-hydroxypropyl)-α-cyclodextrin (HP-α-CD), (2-hydroxypropyl)-β-cyclodextrin (HP-β-CD), (2-hydroxypropyl)-γ-cyclodextrin (HP-γ-CD) and β-cyclodextrin (β-CD) and four flavanones (naringenin, naringin, hesperetin and dihydromyricetin) in aqueous solutions and their phase solubility was determined. For all the flavanones, the stability constants of their complexes formed with different CDs followed the rank order: HP-β-CD (MW 1540) > HP-β-CD (MW 1460) > HP-β-CD (MW 1380) > β-CD > HP-γ-CD > HP-α-CD. Experimental results and quantum chemical calculations showed that the ability of flavanones to form inclusion complex with (2-hydroxypropyl)-cyclodextrins was determined by both the steric effect and hydrophobicity of the flavanones. For flavanones that have similar molecular volumes, the hydrophobicity of the molecule was the main determining factor of its ability to form inclusion complexes with HP-β-CD, and the hydrophobicity parameter Log P is highly correlated with the stability constant of the complexes. Results of thermodynamic study demonstrated that hydrophobic interaction is the main driving force for the formation process of the flavanone–CD inclusion complexes. Quantum chemical analysis of the most active hydroxyl groups and HOMO (the highest occupied molecular orbital) showed that the B ring of the flavanones was most likely involved in hydrogen bonding with the side groups in the cavity of the CDs, through which the inclusion complex was stabilised.

Purpose: To improve the aqueous solubility of phloridzin by complexing it with hydroxypropyl-β-cyclodextrin (HP-β-CD).Methods: The complex of phloridzin with HP-β-CD was prepared by freeze-drying method. The physicochemical properties of the complex were investigated by ultraviolet-visible spectrometry (UV), infrared spectrometry (IR), differential scanning calorimetry (DSC) and x-ray diffractometry (XRD). The antioxidant activity was examined by DPPH and ABTS radical-scavenging activities.Results: Phloridzin in the complex was molecularly dispersed in HP-β-CD matrix. The complex was an effective scavenger of DPPH and ABTS radicals. At a concentration of 0.8 mg/mL and 30 μg/mL, DPPH and ABTS radical scavenging activities of the complex were 83.7 and 74.9 %, respectively.Conclusion: By forming inclusion complex with HP-β-CD, the solubility of phloridzin in water was significantly enhanced. The complex showed strong DPPH and ABTS radical scavenging activities.Keywords: Phloridzin, Hydroxypropyl-β-cyclodextrin, Complex, Antioxidant

A novel microwave assisted multi-stage countercurrent extraction (MAMCE) technique was developed for the extraction of dihydromyricetin from Chinese rattan tea, Ampelopsis grossedentata. The technique combined the advantages of microwave heating and dynamic multi-stage countercurrent extraction and achieved marked improvement in extraction efficiency over microwave assisted batch extraction. Analysis of dihydromyricetin concentrations in the solvent and matrix throughout the extraction process showed that by dividing the extraction into multiple stages and exchanging of solvents between stages, steady and substantial concentration gradients were established between the matrix and solvent, thus enabling the achievement of high extraction efficiency. The yield of dihydromyricetin was significantly affected by temperature, pH, solvent/material ratio and extraction time, and optimal extraction conditions were found to be 80-100°C, at acidic pH with a solvent/material ratio of 25-30 to 1 and extraction time of 5-10 min. With the high extraction efficiency and low usage of extraction solvent, MAMCE could prove to be a promising extraction technique which can be applied to the extraction of dihydromyricentin and other bioactive substances from natural materials.

The extraction of flavonoids from Pteris multifida was optimized to maximize flavonoid yield in this study. A central composite design of response surface methodology involving time, temperature, ratio of liquid to solid and ethanol concentration was used, and second-order model for flavonoid yield was employed to generate the response surface. The optimum condition for flavonoid extraction was determined as follows: temperature 65.6 degrees C, ethanol concentration 58.1%, ratio of liquid to solid 20, time 90 min. The predicted yield at the optimum condition was 2.70%. Experimental verification gave values of 2.66%.

The optimization of acylation of quercetin was studied in this study. Through response surface methodology, the optimum condition was determined as following: molar ratio of quercetin to acetic anhydride 15, addition of pyridine drop 1.00, reaction temperature 45 °C and reaction time 106.59 min. Under this condition, the yield was as high as 0.3814 g with 0.32 g quercetin as raw material.

In the title compound, C(27)H(24)O(14), also known as 2,3-di-acetoxy-5-[(2RS,3RS)-3,5,7-triacetoxy-4-oxochromen-2-yl]phenyl acetate, the heterocyclic ring adopts a distorted half-chair conformation, with two C atoms displaced by 0.1775 (16) and -0.5950 (16) Å from the mean plane of the other four atoms. The dihedral angle between the aromatic rings is 57.81 (8)°. In the crystal, the mol-ecules inter-act by C-H⋯O bonds, aromatic π-π stacking [centroid-centroid separation = 3.6206 (9) Å] and C-H⋯π inter-actions.

Studies on the structure and functions of membrane proteins are impeded by their lability, hydrophobicity, difficulty in purification and low yields. Human chemokine receptor 3 (CCR3) is a G protein-coupled receptor related to allergic diseases. A Triton X-100/PEG20000 two-phase system was employed for enrichment separation of CCR3 over-expressed in E. coli. Optimal CCR3 partitioning with partition coefficient around 8 was obtained at pH 7.0, ionic strength of 0.3 mol/kg and 3 h equilibration time. Total recovery of CCR3 reached 102 ± 15%, which was much higher than 32 ± 5% of the normally used ultracentrifugation method. The recovered CCR3 was finally purified by two chromatography steps giving a final protein of 87 kDa.

This study analyzed 11 Chinese cultivars of marigold to determine their major phytochemical contents and antioxidant activities. Dried marigold flowers were extracted with ethanol, ethyl acetate, and n-hexane and the extracts were analyzed by high-performance liquid chromatography-mass spectrometry and chemical methods to determine their lutein esters, phenolic and flavonoid contents, and antioxidant activity, respectively. The different cultivars of marigold showed considerable variations in their lutein ester contents, ranging from 161.0 to 611.0 mg/100 g of flower (dry basis). The lutein esters in marigolds consisted predominantly of six all trans-diesters, but small amounts of cis isomers of the respective diesters were also present. The different cultivars of marigold also showed marked variations in total phenols and flavonoids, as well as antioxidant and radical-scavenging activities. Ethanol was confirmed to be the best solvent for extracting both phenols and flavonoids from marigold flowers, while n-hexane was the worst. The ethanolic extracts also exhibited the highest antioxidant and radical-scavenging activities. The cultivar Xinhong had the highest phenolic and flavonoid contents and radical-scavenging activity, as well as one of the highest lutein contents and antioxidant activities.

Microwave-assisted extraction (MAE) technique in combination with multi-stage countercurrent extraction (MCE), namely microwave multi-stage countercurrent extraction (MMCE), was evaluated for the extraction of dihydromyricetin (DMY) from Ampelopsis grossedentata. Ethanol, methanol and water were used as extract solvents in the MMCE method. Of the three solvents used, water was found to be the best in extracting DMY from Ampelopsis grossedentata because it had a good extraction. yield and is inexpensive, non-toxic and environmentally friendly The optimal conditions of MMCE for the extraction of DMY can be determined to be the ratio of the extraction solvent to plant material of 30:1, the extraction time of 5 min, the extraction temperature of 110 degrees C and the microwave power of 600 W. In addition, the extraction efficiency of the MMCE method was compared with that of the microwave static batch extraction (MSBE) under the optimum extraction conditions. It was found that the MMCE method offered higher extraction efficiency than the MSBE method. Thus, the study suggests that the MMCE method provides an alternative technique in terms of both cost and efficiency.