高效液相色谱法测定饮料中咖啡因含量研究

用高效液相色谱法测定饮料中的咖啡因,考察了波长、流动相、柱温、流速等因素对可乐中咖啡因测定的影响。结果表明,饮料中咖啡因含量的最佳测定条件为:波长273 nm,流动相为乙腈∶水=20∶80,柱温为20℃,流速为1 mL/min。在0~15μg/mL的浓度范围内线性关系良好(r=0.999 9);加标平均回收率为99.69%。该方法适合于饮料中咖啡因的含量测定,操作简便、快速、灵敏、准确,可作为饮料中咖啡因的质量控制方法。     

Caffeine clearance in the horse

The pharmacokinetic properties of intravenously administered caffeine were studied in 10 horses using a commercially available automated enzyme immunoassay. The harmonic mean for the distribution half-life was 5.2 min (range 1.4–18.7). The harmonic mean for the elimination half-life was 10.18 h (range 6.82–20.92). The harmonic mean of the volume of distribution was 0.32 L/kg (range 0.22–0.53). There was no correlation between the dose of caffeine/kg body weight and the elimination half-life (Spearman's coefficient of rank correlation =0.19).Abbreviations AUC area under the serum concentration-time curve - AUMC area under the moment curve - BSP sulphobromophthalein - ICG indocyanine green - SD standard deviation - t _1/2 elimination half-life - V _c apparent volume of the central compartment - V _d(ss) apparent volume of distribution at steady state     

小种红茶茶多酚和咖啡碱近红外定量分析模型的建立

以76份有代表性的小种红茶为研究对象,采用现行国标方法测定的茶多酚和咖啡碱含量作为近红外预测模型的化学值,对应采集样品的近红外光谱值,分别建立小种红茶茶多酚和咖啡碱含量最佳偏最小二乘法（Partial least squares,PLS）模型。结果表明,所构建的茶多酚含量模型校正集决定系数（Coefficient of determination,R²）为97.59%,校正均方差（Root mean square error of calibration,RMSEC）为0.566%,验证集R²为95.06%,预测均方差（Root mean square error of prediction,RMSEP）为0.855%;咖啡碱含量模型校正集R²为96.98%,RESEC为0.110%,验证集R²为95.67%,RESEP为0.148%。茶多酚和咖啡碱含量定量分析模型效果均较好,可实现对小种红茶茶多酚和咖啡碱含量的快速检测。     

乳酸菌发酵对武夷岩茶咖啡因含量的影响及活性评价

为探明乳酸菌发酵对武夷岩茶主要功能成分的的影响,试验采用超声波辅助萃取和适宜的乳酸菌发酵技术,制备岩茶萃取液和岩茶发酵液,通过HPLC定量分析研究乳酸菌发酵前后武夷岩茶中咖啡因的变化.结果表明,当接种量为6.8×103 CFU/mL,乳酸菌发酵岩茶中咖啡因含量最高达到16.76 mg/g,随着乳酸菌接种量的继续增加,咖啡因含量下降趋势不明显,进行螯合FEC的能力评价结果表明武夷岩茶具有较高的抗氧化活性.     

茶树重要功能基因克隆研究进展

根据发表的文章以及对美国生物技术信息中心（NCBI）的检索结果,从茶树儿茶素类代谢相关基因、咖啡碱代谢相关基因、茶香气形成相关基因等方面介绍茶树重要功能基因分离研究进展。     

Highly efficient induction of triploid Pacific abalone <Emphasis Type="Italic">Haliotis discus hannai</Emphasis> by caffeine treatment

ABSTRACT:   In order to develop a highly efficient method for mass production of triploid Pacific abalone Haliotis discus hannai , caffeine treatment that is safe and inexpensive was optimized. To suppress the first meiotic division, fertilized eggs were exposed to either a 10- or 15-mM caffeine solution for 24 min beginning at 12 min after fertilization. In most treated batches, the rates of cleaved eggs showed no significant difference from the control batches. However, in most treated batches, the rates of occurrence of normal larvae and the survival rates of the early juveniles were significantly lower than those of the controls. The triploid rates at 6 days to 11 months after settlement in all the treated batches were extremely high (91–100%). There was no significant difference in the mean triploid rates between 10- and 15-mM caffeine treatments. These results suggest that both treatment conditions were conducive to triploid abalone production. One live 2n/3n mosaic specimen was found in the treated batches. However, since the frequency of mosaic was extremely low, the mosaicism would probably not have an adverse effect on the stable production of triploid abalones.     

Tea plant (Camellia sinensis L.) roots secrete oxalic acid and caffeine into medium containing aluminum

We examined the response of the tea plant (Camellia sinensis L.) to aluminum (Al) exposure under sterile conditions, focusing specifically on the secretion of low molecular mass organic compounds from roots. After germination in agar medium, tea seedlings together with medium were placed on agar containing 0.4?mM Al with 0.2% hematoxyline (hematoxylin-Al medium). The purple color of the hematoxylin-Al medium was observed to fade gradually, until none of the color remained 6 days later. The tea seedlings were then treated with simple calcium solution (0.2?mM, at pH 4.2) containing AlCl₃, which ranged in concentration from 0 to 0.8?mM, for 24?hrs. The amount of oxalate secreted into the medium increased as the external Al concentration increased, while the concentrations of malate and citrate in the medium remained unchanged. Oxalate secretion started within 30?min after Al exposure and increased linearly thereafter. The findings demonstrated that oxalate was a key compound in the Al-tolerance mechanism employed by the tea plant, which detoxifies Al³⁺ externally in the rhizosphere. In addition to oxalate, caffeine was also secreted by tea roots in response to Al exposure. It is possible that caffeine excretion from the roots of tea plants may stimulate root growth through the inhibition of callose deposition in root tips.     

自模式曲线分辨红外光度法用于咖啡碱—茶碱混合物的不分离定量测定

本文研究了自模式曲线分辩红外光度法及其在多组分结构相似混合物同时定量测定中的应用.测定不同配比(10:1至1:10)咖啡碱—茶碱混合物组分,平均回收率分别为99.2±3.6%与99.1±2.8%,测定雀巢咖啡中咖啡碱的结果为3.37±0.093%.     

A modified extraction and clean-up procedure for the detection and determination of parathion-methyl and chlorpyrifos residues in tea

Recent advances in methodology and instrumentation have made possible the detection and determination of pesticides at microgram kg-1 (ppb) levels. The sensitivity of a method of analysis depends greatly on the efficient extraction of the pesticide and the subsequent clean-up of the extract. The extract from green tea leaves is a mixture of aroma components, polyphenols and caffeine. The preparation of made tea from green tea leaves adds to this complexity by concentrating these coextractives. Conventional clean-up techniques provide poor recoveries for parathion-methyl and chlorpyrifos from both green tea leaves and made tea. This arises from interference by caffeine during gas chromatography, as it has a similar retention time to the two pesticides and peaks overlap. A modification to the protocol based on a solvent partitioning process using dichloromethane and subsequent washing of the extracts with warm water removed the caffeine, and pigments were removed by column chromatography. Recoveries ranging from 80 to 90% were then obtained for both pesticides.     

基于卷积神经网络的茶鲜叶主要内含物的光谱快速检测方法

儿茶素和咖啡碱是茶叶品质的重要评价指标，为了探索深度卷积神经网络(CNN)结合可见近红外光谱(Vis/NIR)用于茶叶儿茶素和咖啡碱无损快速检测的可行性，本研究通过高效液相色谱来测定茶叶中的儿茶素和咖啡碱含量，并与样本的光谱信息建立对应关系；采用回归分析和CNN建模构建了光谱与茶叶内含物的定量关系；采用竞争自适应重加权采样(CARS)和连续投影算法(SPA)选择特征波长，用于开发基于这些特征波长的简单模型。结果表明:4种儿茶素和咖啡碱含量从第1叶位到第6叶位呈现出逐渐降低的趋势；提取特征波长不仅减少了光谱变量数，还获得了比全谱更优或接近的模型性能；CNN在回归分析和特征提取中均表现出良好的性能，预测儿茶素和咖啡碱最优模型的决定系数(R²)和残余预测偏差(RPD)分别达到了0.93和3.28以上。因此，卷积神经网络结合可见近红外光谱可以对儿茶素和咖啡碱的含量进行快速无损检测。