Chromatographic separation and determination of fruit acids

A method is described for the determination of malic, tartaric and citric acids and sugar in fruit juices. It consists of the separation of these constituents by ion-exchange chromatography through a column of Dowex I-X8 with an acetate buffer as eluent, treatment of aliquots of the separated constituents with dichromate and sulfuric acid and measurement of the absorbance of the resultant green chromium(lll).     

Electrochemical Analogue to the Cinnamic Acid Photodimerization

The dimerization reaction that occurs during electrochemical methoxylation of cinnamic acid is analogous to photodimerization and leads to the formation of -truxillic acid in the following cathodic–anodic process: The radical cation that forms on the anode converts into a biradical on the cathode, which then undergoes dimerization to -truxillic acid with a current efficiency of 63% (in a diaphragmless electrolyzer). The current efficiency rises to 94% when an alternating current is used. In a diaphragm electrolyzer -truxillic acid fails to form.     

An LCEC method for the analysis of synthetic amino acids in fruit juices

Summary A fast and simple HPLC-method for the determination of synthetic amino acids in adulterated orange juice has been developed. The amino acid enantiomers were derivatized with a chiral reagent and the derivatives separated on a 3 m particle size C₁₈ column. An electrochemical detector operating in the oxidative mode was used for detection. The potential at which the derivatives are oxidized was determined by cyclic voltammetry.By using selective (electrochemical) detection it is possible to reduce the sample clean-up to simple centrifugation and filtration steps.     

中间态粒子对肉桂醇电化学氧化的影响

讨论了中间态粒子（ｍｅｄｉａｔｏｒ）ＭｎＯ２和ＰｂＯ２对肉桂醇电催化反应的影响。由于二者氧化电位的差异，从而改变了肉桂醇氧化反应生成物的组成。以ＭｎＯ２为中间态粒子时，肉桂醇氧化后的主要生成物是肉桂醛，电流效率高达８０％以上。以ＰｂＯ２为中间态粒子时，肉桂醛将进一步被氧化成肉桂酸，电极反应的选择性明显降低。     

气相色谱-质谱法分析山楂果中的有机酸

山楂(Hawthorn),别名红果,蔷薇科山楂属(Crataegus)植物,山楂果营养丰富,是最早被列入食药兼用的水果之一,具有消食化滞,行气散瘀等功效。山楂果中起消食导滞作用的有效成分是有机酸。本文对文献的实验条件进行合理改进,用GC—MS法对河南辉县和桐柏山两地山楂果中有机酸成分进行了系统分析,各有机酸成分得到有效分离;并利用选择离子方法测定了其中8种主要有机酸的含量,以期对山楂果的食用、药用价值以及开发研制功能性保健食品提供科学依据。     

肉桂酸的催化氧化反应研究

研究了季铵盐催化下高锰酸钾氧化肉桂酸的反应。考察了催化剂、反应时间、温度、高锰酸钾的用量及反应体系的酸碱性对反应的影响。在优化反应条件下,反应产率可达72.30%。     

Determination of phenolic acids in fruit juices by isocratic column liquid chromatography

A simple and rapid analytical method of five phenolic acids, gallic, chlorogenic, caffeic, ellagic and ferulic acid, which are naturally occurring bioactives, were determined in fruit juices by isocratic LC using photodiode array UV detection. The sample was pre-treated by solid-phase extraction (a combination of Sep-Pak Plus tC18 and Bond Elut PSA).     

Photodegradation of Cinnamic Acid in Different Media

The photodegradation of cinnamic acid under UVB irradiation was evaluated in different vehicles, such as water solutions at different pH values, Tween‐20 micelles, liposomes, and O/W emulsions prepared with Xalifin 15 or Montanov 68 as emulsifiers. The increase of pH decreases the photodegradation of cinnamic acid in all the vehicles studied. Micellar solutions showed a protective effect against cinnamic acid photodegradation; this property increases according to the surfactant percentage. Emulsions appeared to be the most efficient protective systems while liposomes had lower ability to protect cinnamic acid against UVB photodegradation.     

肉桂酸类抗氧化剂结构—活性关系研究

利用邻菲罗啉化学发光法研究了中草药有效成分氯原酸、连翘酯甙等肉桂酸类抗氧化剂对HO·的清除作用。量子化学计算[3-21G、B3LYP/6-31G(d)]对实验结果给予了合理的解释。 计算结果显示抗氧化剂形成半醌式自由基前后的能量之差(ΔE)能较好地衡量其活性的高低;抗氧化剂半醌式自由基与邻位取代基形成分子内氢键或通过共振形成邻苯醌可使内能降低,半醌式自由基更稳定;脱氢酚羟基的对位含有给电子取代基团时,可使半醌式自由基易形成并提高其稳定性。