超临界CO_2萃取桑叶总黄酮工艺的研究

采用超临界CO2萃取桑叶总黄酮,以得率为指标,对萃取压力、萃取温度、夹带剂乙醇的浓度和流量等影响因素进行正交试验。结果表明最佳工艺条件为:萃取压力35 MPa,温度55℃,乙醇质量分数90%,乙醇流量0.01 mL/min。此条件下桑叶总黄酮得率2.28%。该方法简便、可靠、选择性高,适于工业化生产。     

银杏叶中硒与多糖的季节分布

银杏叶中总硒和各种溶解形态硒含量随着季节而变化,实验研究了不同采摘期银杏叶中总硒及不同溶解态硒含量分布.7月、9月和霜降之后采摘的银杏叶总硒的含量分别为1.873,2.136,0.815 mg·kg-1,硒的形态以水溶态硒为主.银杏叶粗多糖含量分布依次为9月＞7月＞11月.7月份采集的银杏叶中得到粗多糖为棕褐色固体粉末...     

High performance hybrid reinforcement of nitrile rubber using short pineapple leaf fiber and carbon black

Rubber composites with very high moduli at low elongation, high elongation at break and high ultimate breaking strength have been developed. The matrix was acrylonitrile butadiene rubber (NBR) and the hybrid (fibrous and particulate) reinforcements were short, fine pineapple leaf fiber (PALF) and carbon black. The amount of PALF was fixed at 10 parts (by weight) per hundred of rubber (phr) while that of carbon black was varied from 0 to 30 phr. Uniaxial NBR composites were prepared. Tensile strength, elongation at break, modulus and tear strength of the hybrid composites were characterized in both longitudinal (parallel to the fiber axis) and transverse (perpendicular to the fiber axis) directions. The addition of carbon black causes the slope of the early part of the stress–strain curve to increase and also extends breaking to greater strains. At carbon black contents of 20 phr and above, the stress–strain relation displays an upturn at high elongations, providing greater ultimate strength. Comparison with the usual carbon black filled rubber shows that the composite behavior at low strains is determined by the PALF, and at high strains by the carbon black. This high performance PALF-carbon black reinforced NBR shows great promise for engineering applications.     

Multiconstituent identification in root,branch, and leaf extracts of Juglans mandshurica using ultra high performance liquid chromatography with quadrupole time‐of‐flight mass spectrometry

As a traditional medicinal plant, Juglans mandshurica has been used for the treatment of cancer. Different organs of this plant showed anti‐tumor activity in clinic and laboratory. Comparative identification of constituents in different plant organs is essential for investigation of the relationship between chemical constituents and pharmacological activities. For this aim, the roots, branches, and leaves of J. mandshurica were extracted with 50% v/v methanol and then subjected to ultra‐high performance liquid chromatography with quadrupole time‐of‐flight mass spectrometry analysis conducted under low and high energy. As a result, we have to date identified 111 compounds consisting of 56 tannins, 29 flavonoids, 13 organic acids, 8 naphthalene derivatives, and 5 anthracenes. Five compounds, namely, diquercetin trihydroxy‐truxinoyl‐glucoside, two quercetin kaempferol dihydroxy‐truxinoyl‐glucosides, syringoyl‐tri‐galloyl‐O‐glucose, and dihydroxy‐naphthalene syringoyl‐glucoside, were tentatively identified as new compounds. Of the compounds identified, 76 were found in the root extract, 67 in the branch extract, and 37 in the leaf extract. Only six compounds including four organic acids and two tannins were found in all three extracts. We developed a rapid and sensitive ultra high performance liquid chromatography with quadrupole time‐of‐flight mass spectrometry approach to identify multiple constituents of complex extracts without separation and ion selection. The results presented provide useful information on further research of the bioactive compounds of J. mandshurica .     

Ionic liquid aqueous solvent-based microwave-assisted hydrolysis for the extraction and HPLC determination of myricetin and quercetin from Myrica rubra leaves

An ionic liquid aqueous solvent‐based microwave‐assisted hydrolysis (ILAS‐MAH) approach was proposed for the rapid extraction and accurate determination of myricetin and quercetin from Myrica rubra (M. rubra) leaves for the first time. The effects of the ionic liquid class and concentration, liquid–solid ratio, hydrolysis temperature and time were investigated to obtain the optimal ILAS‐MAH conditions. The optimized conditions were 2.0 mol/L [bmin][HSO4] or 2.5 mol/L acidified [bmin]Br solution, liquid–solid ratio 30:1 (mL : g), hydrolysis temperature 70°C and hydrolysis time 10 min. Under these conditions, the recoveries of myricetin and quercetin were in the range of 86.3–107.3% with relative standard deviation lower than 5.8%. Compared with conventional heating hydrolysis and regular MAH, the proposed approach reduced hydrolysis time and improved yields. The mechanism of ILAS‐MAH was also investigated. Copyright © 2010 John Wiley & Sons, Ltd.     

超声波辅助提取柿子树叶单宁的研究

以70%的丙酮溶液为提取溶剂,采用超声波辅助提取野柿叶中的单宁,考察了超声波的功率、提取温度、提取时间等因素对单宁提取量的影响.采用响应面法对提取条件进行优化,并建立了二次回归模型.实验结果显示:当提取温度为52℃、超声波功率为80 W、提取时间为42 min,在此条件下单宁的提取量为203.15 mr/g,比无超声波...     

不同产地杜仲叶中金属元素的含量及其变化趋势分析

采用火焰原子吸收光谱法测定了陕西杨凌、陕西安康和河南灵宝产杜仲叶中Fe、Cu、Mg、Ca、Mn、Zn 6种金属元素的含量,并对其含量的变化趋势进行了分析比较.结果表明,杜仲叶中含有丰富的人体必需金属元素,且不同产地来源的样品中金属元素的含量有明显差异,其中尤以Fe、Zn、Mn和Mg含量差异最大,Cu和Ca的差异不明显....     

Expanded separation technique for chlorophyll metabolites in Oriental tobacco leaf using non aqueous reversed phase chromatography

An improved separation method for chlorophyll metabolites in Oriental tobacco leaf was developed. While Oriental leaf still gives the green color even after the curing process, little attention has been paid to the detailed composition of the remaining green pigments. This study aimed to identify the green pigments using non aqueous reversed phase chromatography (NARPC). To this end, liquid chromatograph (LC) equipped with a photo diode array detector (DAD) and an atmospheric pressure chemical ionization/mass spectrometer (APCI/MSD) was selected, because it is useful for detecting low polar non-volatile compounds giving green color such as pheophytin a. Identification was based on the wavelength spectrum, mass spectrum and retention time, comparing the analytes in Oriental leaf with the commercially available and synthesized components. Consequently, several chlorophyll metabolites such as hydroxypheophytin a, solanesyl pheophorbide a and solanesyl hydroxypheophorbide a were newly identified, in addition to typical green pigments such as chlorophyll a and pheophytin a. Chlorophyll metabolites bound to solanesol were considered the tobacco specific components. NARPC expanded the number of detectable low polar chlorophyll metabolites in Oriental tobacco leaf.     

无向图可迹的一个充分条件

无向图G是简单连通图,且最小度为δ.如果G中包含一条生成路,则G是可迹的.无向图G的叶子数L(G)是G中生成树所含的叶子数的最大数.基于L(G)和δ,证明了一个充分条件使得无向图G是可迹的,即设G为连通图,最小度为δ≤4.若δ≥(1/2)(L(G)+2),G是可迹的.