利用大孔树脂吸附法分离儿茶素EGCG和咖啡因

考察了S-8、X-5、XAD-200等树脂对绿茶水提液中儿茶素EGCG和咖啡因的吸附性能,结果显示,具有高比表面积的弱极性吸附树脂XAD-200对EGCG和咖啡因的吸附差异较大,动态吸附过程中发生层析分离,儿茶素EGCG在1.5 BV后即开始泄漏,而咖啡因在6 BV后才开始泄漏.收集1.5～6 BV处的流出液可得w（咖啡因）＜0.30％的儿茶素,EGCG的质量分数由48.65％提高至66.37％.在最佳上样量下,EGCG的收率可达65.21％.     

An increase in the influx of calcium ions into cilia induces thigmotaxis inParamecium caudatum

To understand the role of calcium ions in thigmotaxis inParamecium caudatum, the effects of caffeine, ruthenium red and lanthanum (LaCl₃) on thigmotaxis were examined. Thigmotaxis in the CNR mutant, which lacks voltage-dependent Ca²⁺-channels in the ciliary membrane, was also examined. Ruthenium red and LaCl₃ suppressed thigmotaxis inP. caudatum, while caffeine enhanced it. The CNR mutant showed hardly any thigmotaxis. It can be thought that an increase in Ca²⁺ influx and the intraciliary concentration of Ca²⁺ ions induces thigmotaxis inParamecium.     

茶叶中咖啡因检验的设计与改进

针对茶叶咖啡因检测过程中挥发性试剂气味污染严重、易燃易爆试剂购置手续繁琐等问题,通过替换显色剂及氧化剂,增加金属离子络合反应显色等探究性方法,使实验操作便捷、安全可靠,拓展了学生的综合知识,更加适合本科生的实验教学。     

超临界CO2萃取茶叶中咖啡因的实验研究

该文对超临界CO2萃取茶叶中的咖啡因的影响因素进行了实验研究.通过正交实验研究了萃取压力、CO2流量、萃取时间、萃取温度等因素对萃取量的影响,各因素的影响按大小排序依次为压力＞流量＞温度＞时间,适宜的萃取条件为:压力45 MPa,温度65℃,时间240min,CO2流量16 kg/h.夹带剂采用体积分数为50%的CH3CH2OH溶液,其用量对萃取量及选择性均有影响,适宜的夹带剂添加量为120mL.此外还研究了分离部分尤其是一级分离的温度、压力对萃取结果的影响,在压力为12 MPa,温度为44～50℃左右时萃取量和选择性都比较高,选择性受温度和压力影响较大,12 MPa、44℃时选择性最高.     

测定咖啡因的几种方法比较

用紫外吸收光谱、导数光谱及高效液相色谱法测定两种速溶咖啡制品中的咖啡因含量,并对光谱法测定结果与ＨＰＬＣ法测定结果进行统计分析比较。结果表明：用二阶导数光谱法测定速溶咖啡制品中咖啡因,操作简便,结果准确可靠,可替代ＨＰＬＣ法分析此类样品。     

纸基质室温燐光法测定痕量茶碱和咖啡因的研究

该文较详细地研究了混合重原子微扰剂KI—NaAc对茶碱和咖啡因产生室温燐光的影响,以及温度、干燥时间、重原子浓度等适宜条件的选择。实验结果表明,当使用KI—NaAc混合重原子体系时,茶碱和咖啡因产生较强的室温燐光。在适宜的条件下,茶碱和咖啡因的绝对检出限分别为7.2ng和3.1ng;线性范围为1×10~(-3)～5×10~(-4)mol/L和7×10~(16)～9×10~(-4)mol/L。将本法用于茶汤和撒痛风注射液中咖啡因的测定,方法简单、选择性较好,结果较满意。     

Caffeine analogs: biomedical impact

Caffeine, widely consumed in beverages, and many xanthine analogs have had a major impact on biomedical research. Caffeine and various analogs, the latter designed to enhance potency and selectivity toward specific biological targets, have played key roles in defining the nature and role of adenosine receptors, phosphodiesterases, and calcium release channels in physiological processes. Such xanthines and other caffeine-inspired heterocycles now provide important research tools and potential therapeutic agents for intervention in Alzheimer’s disease, asthma, cancer, diabetes, and Parkinson’s disease. Such compounds also have activity as analgesics, antiinflammatories, antitussives, behavioral stimulants, diuretics/natriuretics, and lipolytics. Adverse effects can include anxiety, hypertension, certain drug interactions, and withdrawal symptoms. Received 31 January 2007; received after revision 7 April 2007; accepted 26 April 2007     

微波加热-紫外分光光度法快速测定茶叶中咖啡碱

报道利用微波加热快速抽提茶叶中咖啡碱－紫外分光光度法予以测定,与经典沸水浴浸提法和回流抽提法相比较,测定结果符合,精度水平一致,操作简便,快速,适合于大批量样品分析,经Ｆ检验法及ｔ检验法检验,三种方法的分析结果无明显的差异。     

红外光谱法测定咖啡因的含量

提出和建立一种简便、快速、不使用任何有机溶剂的咖啡因定量分析方法.准确称取定量咖啡因对照品,以铁氰化钾作为内标物,分别加入相同量的铁氰化钾和溴化钾,充分研磨并混合均匀,配制成标准系列.测定ATR-FTIR吸收光谱.选择咖啡因中不受干扰的特征吸收峰羰基峰和铁氰化钾中的特征吸收峰氰基峰,通过咖啡因特征峰吸光度与铁氰化钾特征峰的吸光度的峰高之比与其对应浓度进行线性回归分析,从而获得标准工作曲线.用相同方法对待测咖啡因样品进行测定,通过标准曲线获得待测咖啡因的浓度.结果表明:方法的线性范围为10~250 mg.g-1,其线性回归的相关系数r=0.995 3;采用该方法对样品进行测定的结果与HPLC方法比较获得了满意的结果;回收实验中平均回收率为98.0%~100.5%,该方法准确,可靠,适合咖啡因和其他固体物质的快速定量分析.