Analysis of lipids from cooked beef by thin-layer chromatography with flame-ionization detection

Lipids were extracted from cooked ground beef with methylene chloride/methanol (2:1). The lipids were separated on a silicic acid column, into neutral and polar fractions by elution with methylene chloride, followed by methanol. These fractions were analyzed by Iatroscan thin-layer chromatography with flame-ionization detection instrumentation on Chromarods S-III (silica gelcoated quartz rods). Comparison of cooked beef stored for 0, 4 and 7 d at 4°C indicated that storage caused a decrease in total lipids, an increase in neutral lipids and a decrease in polar lipids, specifically in phosphatidylcholine. These changes in the lipid fraction were associated with meat flavor deterioration and an increase in lipid oxidation.     

Side-chain autoxidation of stigmasterol and analysis of a mixture of phytosterol oxidation products by chromatographic and spectroscopic methods

Although the structure of phytosterols is closely related to cholesterol, there is a gap in knowledge concerning the formation and occurrence of oxidation products from phytosterols. The main objective of this study was to isolate and characterize some side-chain oxidation products formed after autoxidation of stigmasterol. Another objective was to highlight the difficulties in the analysis of phytosterol and a mixture of their oxidation products by GC. Pure stigmasterol was oxidized at 120°C for 72 h in an air-ventilated oven. Preparative TLC separated the oxidation products, and the products were characterized with GC-MS and NMR. In addition to the common ring-structure oxidation compounds, three semipolar oxidation products—24-ethylcholest-5,22-dien-3β,25-diol, 24-ethylcholest-5,22-dien-3β,24-diol, and 24-ethyl-5,22-choladien-3β-ol-24-one—were characterized for the first time by TLC, GC-MS, and NMR. Moreover, the results of the analysis of a large number of oxidation products from sitosterol, campesterol, and stigmasterol by capillary column GC indicated that further efforts and optimization are required in this area.     

Characterization of side-chain oxidation products of sitosterol and campesterol by chromatographic and spectroscopic methods

Based on the cholesterol-lowering effects of phytosterols, known since the 1950s, extra phytosterol amounts have been added to certain food products for almost 10 yr. Literature reports on oxidation of phytosterols in general are limited, and data on side-chain oxidation of these compounds are scarce. The aim of this study was to investigate and characterize autoxidation products from a mixture of the two phytosterols sitosterol and campesterol. A commercial mixture of the two sterols was oxidized for 72 h at 120°C in an air-ventilated oven. The oxidation products were separated by preparative TLC and identified and characterized with GC-MS. The following oxidation products were identified from the two phytosterols: 24-methylcholest-5-en-3β,24-diol, 24-methylcholest-5-en-3β,25-diol, 24-methylcholest-4-en-6α-ol-3-one, 24-methylcholest-4-en-6β-ol-3-one, 24-ethylcholest-5-en-3β,24-diol, 24-ethylcholest-5-en-3β, 25-diol, 24-ethylcholest-4-en-6α-ol-3-one, 24-ethylcholest-4-en-6β-ol-3-one. Full-scan mass spectra of these compounds are reported for the first time as their trimethylsilyl-ether derivatives.     

大豆废料中金雀异黄素含量测定方法的比较

采用乙醇-水溶液从大豆废料中提取大豆异黄酮,初步纯化后,用AB-8大孔吸附树脂进行梯度洗脱得到纯度较高的金雀异黄素样液.样品通过薄层色谱法、紫外分光光度法和高效液相色谱法3种方法测定并做了比较.结果表明:薄层色谱法方法简单,分离效果好;通过紫外分光光度法绘制了标准曲线,可计算样品浓度.该方法准确度高,精密度高,重现性好.加标回收率实验的相对平均偏差RSD为1.04%,精密度实验的相对平均偏差为0.24%,重复性实验的相对平均偏差为0.09%;高效液相色谱法分辨率高、灵敏度高等优点,测得样品纯度为90.1%.     

麦冬皂苷D的分离提纯

以10 kg麦冬为原料,采用甲醇浸提法提取,经过脱脂、脱糖处理后得到18.1g较纯的麦冬总皂苷,得率为0.181％.通过硅胶柱层析法分离纯化麦冬皂苷D,以氯仿-甲醇为洗脱剂进行洗脱,得到麦冬皂苷D样品2.31g,其收率为12.8％,经高效液相色谱检测,分离得到的麦冬皂苷D的纯度为91.2％.结果表明,用硅胶柱层析法可快...     

敦化人参各部位皂苷组分的比较

采用薄层层析、高效液相色谱检测等方法,对敦化产四年白参参头、主根和须根部位皂苷的组成和含量进行测定.研究结果表明,白参各部位中皂苷组成区别不大,参头、主根和须根部位中均含有原人参二醇型皂苷Rb1、Rc、Rb2、Rd和原人参三醇型皂苷Rg1、Re、Rf,其中人参参头部位皂苷含量最高,须根部分次之,主根部分最低.总皂苷质量...     

Arthrobacter sp.3胞外酶转化人参二醇类皂苷生成Rg_3的反应条件

人参稀有皂苷Rg3是具有较高抗癌活性的人参皂苷单体,但在人参中的含量极低。采用新筛选的细菌Arthrobacter sp.3产胞外酶转化人参二醇类皂苷(PPD)生成人参皂苷Rg3,为大量制备人参皂苷Rg3提供了方法。实验结果表明,该细菌产生的人参皂苷酶为胞外酶,通过薄层层析法(TLC)分析得到,最佳发酵诱导物为0.1 mg/mL的PPD,最适反应条件为反应温度40℃、反应时间24 h、底物质量浓度0.1 mg/mL。经HPLC检测,在此条件下反应,产物中Rg3的质量分数为21%。     

基于Qtouch技术的触摸控制旋转LED系统设计

本文利用STM32F103RBT6数字信号处理器和无线收发芯片CC1101以及ATMEGA88V单片机设计主要的硬件电路,实现触摸控制信号的接收处理、发送以及LED屏显示功能。加入LED驱动芯片TLC5947,实现对全彩LED的灰度控制,使原来单一的颜色显示变成全彩显示,效果更加绚烂夺目。     

5-乙酰基-2,3-二氢苯并呋喃的合成

采用邻溴苯酚为初始原料,在相转移催化剂作用下经烷基化合成2-(2-氯乙氧基)-1-溴苯(1),通过生成格氏试剂合成2,3-二氢苯并呋喃(2),由傅-克酰基化反应合成5-乙酰基-2,3-二氢苯并呋喃(3)。反应过程以薄层色谱法监控,并通过元素分析、1HNMR对各中间体的组成和结构进行了确证和表征。     

基于电力载波的路灯电缆防盗报警器设计

介绍了一种基于电力载波技术和模数转换器TLC3548的路灯电缆防盗报警器的硬件和软件设计实现方案。阐述了该方案的原理,即在主机与从机间进行电力载波通信以检测电缆状况,通过单片机控制TLC3548进行数据采集与分析,比较精确地测量出断缆处距路灯现场控制柜的距离,并将信息经GPRS通信模块上报给服务器。经实验证明,该防盗报警器可靠实用,性价比较高。