Use of isothermal microcalorimetry in pharmaceutical preformulation studies

Excipient compatibility of a new chemical entity was assessed using an isothermal microcalorimeter. Mixtures of an active pharmaceutical ingredient with a primary amine group and excipients were prepared in a 1:1 ratio and compatibility monitored by exposing to 50, 60 and 70°C in presence of 200 mL of water. The new chemical entity, a primary amine, reacted with reducing sugars such as lactose and resulted in a brown discoloration. This reaction is the Maillard type condensation reaction between amines and reducing sugars. The rate of reaction was dependent on the temperature with rapid degradation at higher temperatures. No other incompatibility was apparent between the primary amine and other excipients This revised version was published online in July 2006 with corrections to the Cover Date.     

植物组织褐变的研究进展

外植体的褐变是植物组织培养过程中的主要障碍，从酶促褐变的底物和多酚氧化酶出发，阐述了国内外有关外植体褐变的研究现状、褐变发生的机理及防止措施等问题，并对目前所提出的各种机理假说作了评价。     

组织培养过程中污染和褐化的防治

分析了植物组织培养过程中造成污染(真菌污染、细菌污染和潜伏性污染)和褐化的主要原因，同时提出了克服污染和褐化的若干具体措施．     

非酶棕色化反应在烟草增香中的应用研究

文章研究了以天然大豆粉水解液提供氨基酸与葡萄糖或其它羰基化物之间的非酶棕色化反应在烟草增香中的作用，并与己酸和葡萄糖反应的棕色化产物进行对比，认为大豆粉水解液的棕色化产物对烟草增香效果更佳，对烟草薄片的改进作用更为显著。     

薯蓣贮藏期不同部位的褐变生理生化差异

研究了薯蓣贮藏期间不同部位褐变相关的生理生化差异.结果表明:贮藏期间,薯蓣不同部位存在明显的褐变差异.两端的褐变度、总酚含量和多酚氧化酶活性高于中部,皮部的高于心部,使两端和皮部比中部和心部更易和更早发生褐变.两端的过氧化物酶活性高于中部,皮部的高于心部,但心部的过氧化物酶活性15 d后高于中部的,30 d时与两端的相同,这与褐变度的变化规律不同.两端的超氧化物歧化酶活性低于中部,皮部的低于心部,而两端的丙二醛含量高于中部,皮部的高于心部.因此,在薯蓣贮藏过程中,两端和皮部的脂质过氧化程度高于中部和心部,清除自由基的能力则明显低于中部和心部,导致这两个部位膜的完整性更易丧失且易发生褐变.提示薯蓣加工过程中要尽可能抑制两端和皮部的褐变,块茎采摘后不宜长久放置,应及时加工.     

Characterization of polyphenol oxidase from plants

Polyphenol oxidase (PPO) which can mediate browning reaction is a bifunctional copper-containing enzyme encoded by plant nucleolus gene. It usually leads to excessive browning reaction which reduces the coercial profits of fruits and vegetables. In this paper, PPO genes and enzymes in plants are characterized systematically, and the latest progress is reviewed. Some clonings of PPOs genes are reported; the specific temporal and spatial expression pattern of PPOs genes is described; the model of the structure of the precursor form of catechol oxidase is introduced; the possible functions of PPOs in defending against pathogen, wounding, surrounding stress and other inducing factors are demonstrated; the induction and activation of latent PPOs in some plants is elucidated; the scheme of browning inhibition by L-cysteine is clarified; the mechanism of suicide inhibition of latent PPO and kinetic synergism are established. Furthermore, the area for future study is also discussed.     

基于STSE教育理念探秘苹果中的化学知识

《普通高中化学课程标准（2017年版）》强调STSE教育理念。通过对苹果中铁元素、氧气、多酚氧化酶活性对苹果褐变现象影响的实验探究，为提高苹果的使用价值以及食品保鲜技术提供了理论基础，让学习者在"苹果"中感受化学知识的生活化及科学知识的价值。     

Comparison of a Rapid Light-Induced and Forced Test to Study the Oxidative Stability of White Wines

The oxidation processes of white wines can occur during storage and commercialization due to several factors, and these can negatively affect the color, aroma, and quality of the wine. Wineries should have faster and simpler methods that provide valuable information on oxidation stability of wines and allow fast decision-making procedures, able to trigger suitable technological interventions. Using a portable prototype instrument for light irradiations at different wavelengths and times was considered and evaluated on sensorial, spectrophotometric, and colorimetric parameters of white wines. The sensorial analysis revealed that white and light blue were the most significant, after only 1 h of irradiation. The experimental results showed that hydrogen peroxide could enhance the effect of light treatment, allowing a contemporary evaluation of the oxidation stability of wine against light and chemical stresses. As expected, a good correlation (R² > 0.89) between optical density at 420 nm and b* parameter was highlighted. The synergic effect of light and H₂O₂ was also studied on the hydrolyzable and condensed tannins’ additions to white wine. The proposed methodology could be used to evaluate the oxidative stability of white wines, but also to evaluate the effect of some oenological adjuvants on wine stability.     

新型速冻荔枝果皮抗褐变剂（KH－1）的作用机理

本文从生理学、生物化学、形态解剖学和组织化学等多种角度探讨新型速冻荔枝果皮抗褐变剂（ＫＨ－１）的作用机理。结果表明：ＫＨ－１具有螯合铜离子，阻隔氧气，吸附单宁，调节ｐＨ与水分等多种能力。     

Inclusion of Polyphenol Oxidase Substrates in β-Cyclodextrin: A 1 H-NMR Study

A ¹H-NMR study of the interactionsbetween -cyclodextrin (-CD) and included phenolic molecules (chloragenic acid and caffeic acid ) in aqueous medium is reported. The results confirm that inclusion occurs. Data analysis by the continuous variation method shows that all the complexes have 1 : 1 stoichiometries. Values for the apparent association constants of the inclusion compounds are estimated and compared with previously reported values.