In vitro Antioxidant Activity of Ubiquinone and Ubiquinol,Compared to Vitamin E

Coenzyme Q10 (CoQ10) is the prevalent ubiquinone in human organism, largely present in its reduced form, ubiquinol (QH₂), to which the antioxidant, free radical scavenger activity is ascribed by many authors. However, some studies indicate that also the oxidized form presents some effect in preventing the cellular oxidative stress. In this article four in vitro chemical test methods (TEAC, FRAP, DPPH, and BR) were used to assess the free radical scavenging power of CoQ10, QH₂, and vitamin E. The results showed that CoQ10 is almost ineffective, while in three of the tests QH₂ presents a higher antioxidant activity than vitamin E. From these results, it can be concluded that the interconversion CoQ10?QH₂ leading to the prevalence of QH₂ in biological tissues is responsible for the antioxidant action of coenzyme Q10 in living organisms.     

Electrochemical energy for living systems

Plastoquinone and ubiquinone play essential roles in the electron transport chains of chloroplasts and mitochondria by coupling electron transport to the transfer of protons across membranes. The energy of the resulting proton gradient is used to synthesize adenosine triphosphate (ATP), the energy currency of all life. How did quinones first become involved in this process? We have detected several quinone compounds in carbonaceous meteorites that can transport protons in a liposome model system. It is possible that such compounds were available to transport protons in primitive versions of electron transport in early life.     

带有长侧链醌类化合物的Langmuir膜及其表面电势

泛醌(Ubiquinone)和质体醌(Plastoquinone)作为非蛋白电子载体存在于动物线粒体呼吸链和植物光合作用链中.这两类物质在生物膜上有活性.     

Chemiluminescence assay for quinones based on generation of reactive oxygen species through the redox cycle of quinone

A sensitive and selective chemiluminescence assay for the determination of quinones was developed. The method was based on generation of reactive oxygen species through the redox reaction between quinone and dithiothreitol as reductant, and then the generated reactive oxygen was detected by luminol chemiluminescence. The chemiluminescence was intense, long-lived, and proportional to quinone concentration. It is concluded that superoxide anion was involved in the proposed chemiluminescence reaction because the chemiluminescence intensity was decreased only in the presence of superoxide dismutase. Among the tested quinones, the chemiluminescence was observed from 9,10-phenanthrenequinone, 1,2-naphthoquinone, and 1,4-naphthoquinone, whereas it was not observed from 9,10-anthraquinone and 1,4-benzoquinone. The chemiluminescence property was greatly different according to the structure of quinones. The chemiluminescence was also observed for biologically important quinones such as ubiquinone. Therefore, a simple and rapid assay for ubiquinone in pharmaceutical preparation was developed based on the proposed chemiluminescence reaction. The detection limit (blank + 3SD) of ubiquinone was 0.05 μM (9 ng/assay) with an analysis time of 30 s per sample. The developed assay allowed the direct determination of ubiquinone in pharmaceutical preparation without any purification procedure. Figure Chemiluminescence generated through the redox cycle of quinone     

具有长侧碳链的苯醌类化合物在LB膜上的电化学行为

用LB膜技术将含有长侧碳链的泛醌或质体醌类似物转移到导电玻璃上，用循环伏安法研究了它们的电化学行为．发现醌环上的取代基对其电化学行为有明显影响，提出了泛醌类似物和质体醌类似物在LB膜上的具体电化学过程．     

鳙鱼心中电子载体泛醌化合物的研究

鳙鱼（Ａｒｉｓｔｉｃｈｔｈｙｓｎｏｂｉｌｉｓ）心脏提取物经硅胶柱色谱分离、制备薄层色谱纯化，得到二种泛醌化合物，用ＮＭＲ、ＩＲ、ＭＳ、ＵＶ、ＨＰＬＣ、ＴＬＣ等现代测试技术测定其化学结构为２，３－二甲氧基－５－甲基－６－１０聚异戊二烯基－１，４－苯醌（Ⅰ）和一种未见报道的新泛醌酯——２，３－二甲氧基－５－甲基－６－甲酯基－八聚异戊二烯基－１，４－苯醌（Ⅱ）。     

用泛醌修饰的碳糊电极作葡萄糖传感器

本选择泛醌作酶电极电子传统递体，将它和葡萄糖氧化酶、碳糊混和组成一种新的葡萄糖传感器，电极性能较不含泛醌的电极更优越，峰高ｉｐ与葡萄糖浓度在０．８×１０＾－５－１．６×１０＾－４ｍｏｌ／Ｌ范围内呈线性关系，电极灵敏度较高，干扰少，响应快，使用寿命长达三周。     

Structure-activity analysis of fluorinated 1-N-arylamino-1-arylmethane-phosphonic acid esters as inhibitors of the NADH:ubiquinone oxidoreductase (complex I)

Summary The structural and electronic properties of fluorinated 1-N-arylamino-1-arylmethanephosphonic acid esters were studied and related to the inhibitory effects on NADH:ubiquinone oxidoreductase (complex I). Electrostatic potential surfaces, dipole moments and molecular geometries were analysed. Based on the conformational analysis and the electronic parameters, a simple model for the active site of the fluorinated 1-N-arylamino-1-arylmethanephosphonic acid esters was developed, explaining the inhibitory power. The strongest inhibition effects were found for the 1-(N-4-trifluoromethoxyphenyl)-amino-1-phenylmethanephosphonic acid diethyl ester 1bab.     

In situ spectroeletrochemistry and cytotoxic activities of natural ubiquinone analogues

Quinones are a group of potent antineoplastic agents. Here we described effective and facile routes to synthesize a series of ubiquinone analogues (UQAs). These unique compounds have been investigated by electrochemistry and in situ UV-vis spectroelectrochemistry to explore their electron-transfer processes and radical properties in aprotic media. The structure-activities relationships of inhibiting cancer cell proliferation of UQAs were examined in murine melanoma B16F10 cells using a 72 h continuous exposure MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Our results revealed that UQAs had improved antiproliferative activity and displayed better inhibitory effects than natural ubiquinone 10. The cytotoxic activities of UQAs were correlated to the semiubiquinone radicals, which were confirmed by in situ electron spin resonance (ESR). In the cytotoxicity test, 6-vinylubiquinone 5 and 6-(4′-fluorophenyl) ubiquinone 7 that possess half maximal inhibitory concentration value (IC₅₀) of 6.1 μM and 6.2 μM. This would make them as valuable candidates for future pharmacological studies.