赤水绵竹叶黄酮提取工艺方法研究

以芦丁为标准品,以贵州省赤水市绵竹叶为实验对象,对竹叶黄酮的提取进行研究,以乙醇浓度、反应温度、料液比、反应时间为主要考察因素,进行L9（3^4）正交实验,对竹叶黄酮提取条件进行系统研究,确定黄酮最佳提取工艺为乙醇提取浓度75％,反应温度70℃,料液比1：20,反应时间5．5h。     

Hot-pressurized fluid extraction of flavonoids and phenolic acids from Brazilian propolis and their cytotoxic assay in vitro

This work has examined the hot-pressurized fluid extraction of seven flavonoids, caffeic acid phenethyl ester and four phenolic acids from Brazilian propolis lumps generating, during the process, fat- and water-soluble extracts. The solid content of water-soluble extract obtained by hot-pressurized water in the presence of 29% natural surfactant was 35.2 mg/mL and was 44% greater than that obtained without natural surfactant. Furthermore the amount of the seven flavonoids and caffeic acid phenethyl ester in the fat-soluble extract exceeded those in the water-soluble sample while, on the other hand, the amount of the four phenolic acids in the water-soluble extract was more than those in the fat-soluble extract. Our findings show that the total solid content and the amount of these 12 active compounds produced by the emulsified hot-pressurized water are 36% and 7% higher, respectively, than those produced by emulsified water at atmospheric pressure. The EC₅₀ value of the free radical scavenging activity of 1,1-diphenyl-2-picrylhydrazyl of the emulsified hot-pressurized water extract was the lowest, and presented the strongest anti-oxidation ability among all the extracts. In vitro cytotoxicity indicated that the water-soluble extract strongly suppressed the growth of leukemia (HL-60, U937), lung cancer (A549, CH27) and liver cancer (Hep G2, Hep 3B) cells in a concentration-dependent behavior.     

Optimizing color fading effect of cotton denim fabric by enzyme treatment

In this article, the effect of enzyme treatment using neutral cellulase on the color fading property of cotton denim fabric was studied. Four enzyme processing parameters namely treatment temperature, treatment time, pH value, and agitation were considered. To investigate the optimum condition for the enzyme treatment, an orthogonal analysis was used and, based on the K/S summation value (K/S Sum), the optimum condition for enzyme treatment in this study was treatment temperature = 50°C; treatment time = 30 min; pH value = 8; and agitation = 50 steel balls (simulated mild agitation) for the best color fading achievement with desired worn and aged effect. Meanwhile, the level of importance based on the orthogonal analysis was in the order: treatment temperature > treatment time > agitation > pH and the effect of each processing factors was also discussed. In addition, other properties like CIE Lab values, weight loss, and color fastness to laundering and crocking were also evaluated. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of ethanol content on supercritical carbon dioxide extraction of caffeine from tea stalk and fiber wastes

This study presents the effect of ethanol content on supercritical carbon dioxide extraction of caffeine from tea plant wastes. Tea stalk and fiber wastes of Turkish tea plants that have no economical value were evaluated as raw material throughout the caffeine extraction experiments. These wastes were supplied from tea factory marked “Çaykur” in the east blacksea region. They were separately ground, sieved and dried at 105 °C temperature in an oven. Parameters affecting caffeine leaching from tea wastes were determined to be, ethanol flow rate, extraction time, extraction temperature, carbon dioxide flow rate, process pressure and particle size. The maximum yield of caffeine from tea stalk wastes and fiber wastes were 14.95 mg/g tea stalk and 18.92 mg/g tea fiber, respectively. When the supercritical extraction conditions used of ethanol as cosolvent have been compared with the conditions of used only carbon dioxide, approximately the same yield has been reached at 2 h extraction period instead of 7 h. Beside of saving of the time and the amount of carbon dioxide, the supercritical extraction yield with cosolvent increase had been recorded as 62.5% and 63.1%, respectively, in comparison with the chloroform extraction as conventional method of tea stalk and fiber wastes.     

Antioxidant activity of tea extracts in lipids and correlation with polyphenol content

The present study examined the antioxidative activity of water and ethanol extracts of green and black tea leaves against the oxidation of heated sunflower oil and lard. Oxidation was conducted at 110 °C in the Rancimat test. Total polyphenols and catechin contents in tea extracts were measured. The research showed that the total polyphenol content in green and black tea leaves was 205.2 and 148.7 mg/g, respectively. In tea leaves extracts, it ranged between 245.9 mg/g and 837.7 mg/g and depended on the extraction solvent and the kind of tea used (p <0.001). The highest polyphenol content was observed in samples extracted with 95% ethanol, lower contents were found with the use of water. Results showed that the highest antioxidant activity, measured as an induction period, with 1000 ppm green tea ethanol extract, was comparable to á‐tocopherol activity in sunflower oil. In lard, the longest induction period was measured with 500 and 1000 ppm of green tea ethanol extract. Other tea extract concentrations were significantly less active. Statistical analysis of the tea extract antioxidant activity in lipids in the Rancimat test showed an essential influence of the catechin contents. Further statistical analysis also showed an influence of (?)‐epicatechin gallate (ECG), (?)‐epicatechin (EC), and (+)‐catechin (C) contents in the tea extracts on the antioxidant activity in lipids. It was stated that the antioxidant activity was higher in tea extracts containing high levels of ECG, EC, and C.     

A novel process for extraction of tea oil from Camellia oleifera seed kernels by combination of microwave puffing and aqueous enzymatic oil extraction

The objective of this study was to extract the oil from Camellia oleifera seed kernels by aqueous enzymatic oil extraction (AEOE). We describe a novel process for extraction of tea oil preceded by tea saponin extraction from C. oleifera seed kernels. The extraction efficiency obtained with microwave‐assisted extraction (MAE) is very high, which the recovery yield is up to 83% in 30 s and the saponins in camellia seed kernels can be completely removed by the second MAE. Moreover, an important step in the process development has been the pretreatment by microwave puffing of camellia seed kernel residues followed by AEOE increased oil extraction yield from 53% to 95%, which will is comparable to hexane oil extraction yields from plant materials.     

酶辅助提取金银花中绿原酸与多糖的工艺研究

以金银花为原料,进行了酶法辅助同时提取金银花绿原酸与多糖的工艺优化研究,考察提取温度、酶用量、提取时间对提取得率的影响。结果表明,该工艺可以同时实现对金银花绿原酸和多糖这两种活性物质的提取;提取最佳工艺参数为:提取温度50℃,提取时间120 min,酶用量0.5%,金银花绿原酸得率为4.90%,金银花多糖得率为6.58%。     

酶辅助提取金银花中绿原酸与多糖的工艺研究

以金银花为原料,进行了酶法辅助同时提取金银花绿原酸与多糖的工艺优化研究,考察提取温度、酶用量、提取时间对提取得率的影响。结果表明,该工艺可以同时实现对金银花绿原酸和多糖这两种活性物质的提取;提取最佳工艺参数为:提取温度50℃,提取时间120 min,酶用量0.5%,金银花绿原酸得率为4.90%,金银花多糖得率为6.58%。     

Optimization of subcritical water extraction of antioxidants from Coriandrum sativum seeds by response surface methodology

Subcritical water extraction (SWE) of antioxidants from Coriandrum sativum seeds (CSS) was optimized by simultaneous maximization of the total phenolics (TP) and total flavonoids (TF) yield and antioxidant activity, using IC₅₀ value. Box–Behnken experimental design (BBD) on three levels and three variables was used for optimization together with response surface methodology (RSM). Influence of temperature (100–200 °C), pressure (30–90 bar) and extraction time (10–30 min) on each response was investigated. Experimentally obtained values were fitted to a second-order polynomial model and multiple regression. Analysis of variance (ANOVA) was used to evaluate model fitness and determine optimal conditions. Moreover, three-dimensional surface plots were generated from employed mathematical model. The optimal SWE conditions obtained in simultaneous optimization were temperature of 200 °C, pressure of 30 bar and extraction time of 28.3 min, while obtained values of TP and TF yields and IC₅₀ value at this experimental point would be 2.5452 g GAE/100 g CSS, 0.6311 g CE/100 g CSS and 0.01372 mg/ml, respectively. Moreover, good and moderate linear correlation was observed between antioxidant activity (IC₅₀ value) and total phenolics content (R² = 0.965), and total flavonoids content (R² = 0.709) which indicated that these groups of compounds are responsible for antioxidant activity of C. sativum extracts.     

An enzyme module system for the synthesis of dTDP-activated deoxysugars from dTMP and sucrose

A flexible enzyme module system is presented that allows preparative access to important dTDP-activated deoxyhexoses from dTMP and sucrose. The strategic combination of the recombinant enzymes dTMP-kinase and sucrose synthase (SuSy), and the enzymes RmlB (4,6-dehydratase), RmlC (3,5-epimerase) and RmlD (4-ketoreductase) from the biosynthetic pathway of dTDP-beta-L-rhamnose was optimized. The SuSy module (dTMP-kinase, SuSy, +/-RmlB) yielded the precursor dTDP-alpha-D-glucose (2) or the biosynthetic intermediate dTDP-6-deoxy-4-keto-alpha-D-glucose (3) on a 0.2-0.6 g scale with overall yields of 62 % and 72 %, respectively. A two-step strategy in which the SuSy module was followed by the deoxysugar module (RmlC and RmlD) resulted in the synthesis of dTDP-beta-L-rhamnose (4; 24.1 micromol, overall yield: 35.9 %). Substitution of RmlC by DnmU from the dTDP-beta-L-daunosamine pathway of Streptomyces peucetius in this module demonstrated that DnmU acts in vitro as a 3,5-epimerase with 3 as substrate to yield 4 (32.2 mumol, overall yield: 44.7 %). Chemical reduction of 3 with NaBH4 gave a mixture of the C-4 epimers dTDP-alpha-D-quinovose (6) and dTDP-alpha-D-fucose (7) in a ratio of 2:1. In summary, the modular character of the presented enzyme system provides valuable compounds for the biochemical characterization of deoxysugar pathways playing a major role in microbial producers of antibiotic and antitumour agents.     

Improved extraction of metallofullerenes with DMF at high temperature

Gd, Tb, Y, Sm-metallofullerenes were extracted with DMF by high-temperature extraction or by Soxhlet extraction. The extractable residues were then dissolved in toluene for further HPLC separation, respectively. Comparison of the mass spectra and HPLC chromatograms of the toluene solutions from the two extraction methods indicated that the one-step high-temperature-DMF extraction was more effective and convenient. By using the high-temperature-DMF method, the extraction efficiency of Gd@C₈₂ was 15 times higher than that by Soxhlet extraction. The studies of other Gd-monometallofullerenes, Gd-dimetallofullerenes and Tb, Y, Sm-metallofullerenes gave similar results. Some possible reasons are proposed.     

Coimmobilization of malic enzyme and alanine dehydrogenase on organic–inorganic hybrid gel fibers and the production of L‐alanine from malic acid using the fibers with coenzyme regeneration

Malic enzyme (EC 1.1.1.39) and alanine dehydrogenase (EC 1.4.1.1) were entrap‐immobilized on hybrid gel fibers of cellulose acetate (CA) and zirconium (Zr) alkoxide by air‐gap wet spinning. The production of L ‐alanine from malic acid with coenzyme regeneration was examined with the enzymes immobilized on the fibers. The productivity of L ‐alanine of the immobilized enzymes decreased to approximately one‐fifth of that of free enzymes, but the CA–Zr‐fiber‐immobilized enzymes retained a high level of productivity after repeated use. Reduced form of nicotinamide adenine dinucleotide (NADH) recycling also occurred effectively for the enzymes immobilized on the fiber. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

超声波条件下酶法提取鳝鱼皮中胶原蛋白的工艺研究

对鳝鱼皮中胶原蛋白的最佳提取工艺条件进行了研究.以超声提取时间、胰蛋白酶加入量、酶解时间、提取温度、pH 5个因素对提取工艺条件进行了优化,结果表明,最佳提取工艺条件为:酶加入量125 U/g、pH=7.2、温度35 ℃、超声波辅助提取时间3 min、酶解时间7 h,胶原蛋白的提取率达92.4%.利用紫外光谱和傅立叶变换红外光谱对胶原蛋白进行分析,结果表明,胶原蛋白的紫外特征吸收波长为226 nm,结构中含有肽键,羰基,羧基等蛋白质的特征官能团.     

The supercritical carbon dioxide extraction of polyphenols from Propolis: A central composite design approach

The influence of different parameters on the Supercritical Carbon Dioxide (SCO₂) extraction of Italian Propolis were studied with attention to extraction yield and chemical composition of obtained fractions. Operating parameters of SCO₂ were optimized using central composite design. Analysis by multiple regression indicated that pressure and time have a major linear effect on the extraction yield and extract composition.Propolis SCO₂ extracts present different chemical content compared to the ethanolic extract obtained with ultrasound assisted extraction (UAE). SCO₂ extract can be used to perform further UAE ethanol extraction obtaining a flavonoid containing extract. These findings indicate two possible applications of supercritical carbon dioxide for Propolis extraction, one to obtain lipophilic fractions enriched in specific constituents, the other as pre-treatment of the crude material to facilitate the further extraction with ethanol.     

Optimization of extraction of bulk enzymes from spent mushroom compost

The profiling of ligninase, hemicellulase and cellulase of Pleurotus sajor‐caju after inoculation of spawn in bags containing sawdust was done at monthly intervals for a period of 6 months. Xylanase (EC 3.2.1.8) was produced throughout the 6 months studied with the productivity range from 5.60 to 7.51 U g^?1. Cellulase (EC 3.2.1.4) and β‐glucosidase (EC 3.2.1.21) productivities were highest at 4 months, producing 3.31 U g^?1 and 121.13 U g^?1 respectively. Laccase (EC 1.10.3.2) productivity was highest at 2 months with a value of 7.59 U g^?1. Lignin peroxidase (EC 1.11.1.14) productivity was highest at 5 months with a value of 206.20 U g^?1. Total soluble proteins were highest at 4 months with a value of 0.139 mg cm^?3. The profiling of lignin peroxidase in 5‐month‐old spent mushroom compost was monitored over a period of 10 months. It was observed that lignin peroxidase was produced throughout the period but productivity was variable. The average lignin peroxidase productivity ranged from 30 to 110 U g^?1. The activities of the enzymes extracted in tap water at pH 8.4 were comparable to that extracted in 50 mmol sodium citrate buffer at pH 4.8 and distilled water at pH 5.2 at 4 °C using an incubator shaker at 200 rpm for 18 h. The optimum extraction time was 1 h using an incubator shaker at 4 °C. When an incubator shaker was used, there was no significant difference in the recovery of xylanase, cellulase and laccase at different pH values at 4 °C and 28 °C. No significant difference was observed in the recovery of β‐glucosidase using an incubator shaker at different pH values at 4 °C although the enzyme recovery was slightly higher at pH 8.12, with a value of 29.27 U g^?1. The optimum extraction of β‐glucosidase was at pH 4 at room temperature using an incubator shaker. For the lignin peroxidase enzyme, the optimum pH for extraction was 6 at 4 °C and pH 7 at room temperature using an incubator shaker at 200 rpm for 1 h. Homogenization for 8 min at 8000 rpm using tap water at pH 4 had an advantage over the use of the incubator shaker for the extraction as high titers of enzymes were recovered. Copyright © 2003 Society of Chemical Industry     

Negative pressure cavitation accelerated processing for extraction of main bioactive flavonoids from Radix Scutellariae

To enhance the extraction efficiency and reduce the energy consumption, an emerging technology named negative pressure cavitation extraction (NPCE) has been shown to be a feasible option for the extraction of bioactive compounds in agricultural crops and medicinal plants. Meanwhile, it can be applied at the pilot scale as a manufacturing process for edible and medicinal plants. Currently, NPCE was proposed for extraction of baicalin, wogonoside, baicalein and wogonin from Radix Scutellariae on the basis of a central composite design (CCD) and response surface methodology (RSM). With proper optimization (80 mesh of particle size, 40 mL/g of liquid/solid ratio, 75% aqueous ethanol as extraction solvent, 60 min extraction time and −0.07 MPa vacuum degree), NPCE was observed to have good extraction efficiency compared with other conventional extraction methods. Furthermore, the antioxidant activities of crude extracts with different extraction methods were assessed by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging assay. Our results showed that NPCE extract possessed better antioxidant activity with IC₅₀ value of 3.24 μg/mL compared with the UAE, HRE and SE extracts with IC₅₀ values of 7.85, 12.14 and 11.44 μg/mL, respectively.     

Highly simplified preparation of tea flavonoids from surplus tea leaves by the novel three-phase extraction and purification

A novel three-phase extraction and purification procedure was developed to prepare high-quality flavonoids from surplus tea leaves. Flavonoids were selectively extracted in ethyl acetate (EtOAc) by the EtOAc-water-leaf three-phase extraction, with 91.2% extraction efficiency, more than 50% higher than the traditional water extraction. The EtOAc extracts were purified by the EtOAc-water- montmorillonite/charcoal three-phase adsorptive purification at 98% recovery. Highly purified flavonoids were obtained with less than 1.0% caffeine. The overall flavonoid recovery reached 90.3%, more than 40% higher than traditional methods. This procedure highly simplified the processes and significantly increased the recovery of flavonoid production from tea leaves.     

Supercritical fluid extraction of flavonoids from Maydis stigma and its nitrite-scavenging ability

Supercritical fluid carbon dioxide (SF-CO₂) extraction (SFE) of flavonoids from Maydis stigma and its nitrite-scavenging ability were investigated. The effects of extraction time, particle size and co-solvent composition in terms of water content in ethanol were first optimized. Then, a Box-Behnken design combined with response surface methodology (RSM) was employed to study the effects of three independent variables (temperature, pressure and co-solvent amount) on the extraction yield of flavonoids. A maximal extraction yield of flavonoids of approximately 4.24 mg/g of M. stigma by SFE was obtained under optimal conditions (a temperature of 50.88 °C, a pressure of 41.80 MPa, a co-solvent amount of 2.488 mL/g and an extraction time of 120 min with 0.4-mm particle sizes and 20% aqueous ethanol as the co-solvent). Furthermore, the nitrite-scavenging ability of the flavonoid-enriched SFE extracts was assessed using the Griess reagent. The flavonoid-enriched SFE extracts exhibited the highest scavenging ability on nitrite (88.1 ± 3.04%) at the concentration of 500 μg/mL and at pH 3.0. The nitrite-scavenging ability of the extracts appeared to be concentration dependent but negatively correlated with the pH.     

白豆中α-淀粉酶抑制剂的提取及其酶学性质的研究

对白豆中的α-淀粉酶抑制剂进行了提取和酶学性质研究。以淀粉为底物,酶反应的最佳条件为:温度45℃,pH=6.0。该酶在酸性条件下稳定性较差,在pH 5~7时较稳定;在温度低于40℃时稳定,高于70℃时酶活性全部丧失;Fe2+,Co2+,Zn2+,Mn2+,Cu2+对α-淀粉酶抑制剂具有明显的抑制作用。     

Functionalization of oxidases with peroxidase activity creates oxiperoxidases: a new breed of hybrid enzyme capable of cascade chemistry

The covalent flavoprotein alditol oxidase (AldO) from Streptomyces coelicolor A3(2) was endowed with an extra catalytic functionality by fusing it to a microperoxidase. Purification of the construct resulted in the isolation of a synthetic bifunctional enzyme that was both fully covalently flavinylated and heminylated: an oxiperoxidase. Characterization revealed that both oxidase and peroxidase functionalities were active, with the construct functioning as a single-component xylitol biosensor. In an attempt to reduce the size of the oxidase-peroxidase fusion, we replaced portions of the native AldO sequence with the bacterial cytochrome c CXXCH heme-binding motif. By mutating only three residues of the AldO protein we were able to create a functional oxidase-peroxidase hybrid.