Photochemical properties of selected flavonol dyes: Effects on their separation using capillary electrophoresis

Flavonols are naturally occurring dyes that can be extracted from plants. Because of their antioxidant properties, they are thought to have health benefits. In this study, the photochemical degradation properties of selected flavonols were investigated. Dilute solutions of dyes were exposed to light from a broadband visible light source, and the rate of photodegradation was determined by measuring the decrease in fluorescence of the dyes with respect to time. At pH 9.24, the first-order rate constants for 10?µg?mL^?1 solutions of myricetin, quercetin, kaempferol, and morin were 0.468, 0.162, 0.108, and 0.126?s^?1, respectively. Interestingly, the stability of these historical dyes was also found to be greatly affected by pH. Awareness of the photochemical properties and stability of flavonol dyes is very important for capillary electrophoresis (CE) separations. Photodegradation of the flavonol dyes under the alkaline conditions (pH 9.2) used in CE can have a profound effect on the reproducibility of repeated separations. Even a modest decrease in pH (pH 8.5) greatly improved the stability of these dyes and enabled the successful separation of these flavonol dyes with minimal degradation over time.     

光谱法与分子模拟技术研究杨梅素与牛血清白蛋白的相互作用

利用紫外光谱、荧光光谱、红边激发荧光位移(REES)法、圆二色谱(CD)结合分子模拟技术共同研究了模拟生理条件下杨梅素与牛血清白蛋白(BSA)的相互作用,阐述了相互作用机制.分子模拟结果表明,杨梅素与蛋白在亚结构域II A的疏水腔内结合,主要作用力为疏水作用力和氢键.依据荧光猝灭法判断猝灭机制为静态猝灭,并得到不同温度下药物与蛋白相互作用的结合常数(Ka)及结合位点数(n),根据热力学参数判断出作用力类型,并且计算出杨梅素与蛋白的结合距离,与分子模拟得到的判定结果基本一致.通过紫外光谱、同步荧光光谱以及REES法获得的信息讨论了相互作用时BSA中色氨酸(Trp)微环境的变化;并利用CD谱的测定结果定量计算了BSA二级结构中α-螺旋含量的变化.     

杨梅酮的电化学和光谱性质研究

应用循环伏安和紫外光谱法研究杨梅酮氧化还原性质及其稳定性.结果表明:在B-R缓冲溶液中玻碳电极上,杨梅酮的氧化还原表现为两步氧化反应和两步还原反应.氧化反应对应于B环4-′OH和C环3-OH的氧化,还原反应对应于C环4位羰基还原为中间体自由基之后再进一步还原生成羟基.以上各步反应均为单电子单质子电极过程.杨梅酮的氧化还原反应与溶液pH关系密切,但其原因来自于去质子化作用,并导致它的抗氧化能力增强,但其最终氧化产物没有电化学活性,并吸附在电极表面,阻碍了电极过程电子传递.在pH 7.45~12.00范围内,杨梅酮也因去质子化作用导致紫外光谱Ⅰ带和Ⅱ带随pH增加,而发生红移,分解作用加剧.同时分解作用还与放置时间有关.     

含喹唑啉硫醚的杨梅素衍生物的设计、合成及生物活性研究

以杨梅苷为原料,通过活性拼接,设计并合成一系列含喹唑啉硫醚的杨梅素衍生物,其结构通过1H NMR、13C NMR、19F NMR和HRMS进行确证.生物活性测试结果表明,该类化合物对水稻白叶枯病菌(X.Oryzae)、柑橘溃疡病菌(X. Citri)和烟草青枯病菌(R. Solanacearum)表现出一定的抑制活性.其中, 5,7-二甲氧基-3-(3-((6-溴喹唑啉-4-基)硫基)丙氧基)-2-(3,4,5-三甲氧基苯基)-4H-色烯-4-酮(A15)对水稻白叶枯病菌的EC50值为13.9μg/mL,优于对照药叶枯唑(88.9μg/mL)和噻菌铜(68.1μg/mL);5,7-二甲氧基-3-(4-((6-氯喹唑啉-4-基)硫基)丁氧基)-2-(3,4,5-三甲氧基苯基)-4H-色烯-4-酮(A3)、5,7-二甲氧基-3-(3-((6-氯喹唑啉-4-基)硫基)丙氧基)-2-(3,4,5-三甲氧基苯基)-4H-色烯-4-酮(A14)、5,7-二甲氧基-3-(3-((6-溴喹唑啉-4-基)硫基)丙氧基)-2-(3,4,5-三甲氧基苯基)-4H-色烯-4-酮(A15)和5,7-二甲氧基-3-(3-((6-氟喹唑啉-4-基)硫基)丙氧基)-2-(3,4,5-三甲氧基苯基)-4H-色烯-4-酮(A16)对烟草青枯病菌的EC50值分别为1.1,14.0,11.9和7.5μg/mL,优于对照药叶枯唑(38.5μg/mL)和噻菌铜(184.8μg/mL).活体实验结果表明,化合物A15对水稻白叶枯病菌的具有良好治疗活性和保护活性.通过扫描电镜成像初步探讨了目标化合物A3对烟草青枯病菌和A15对水稻白叶枯病菌的抑菌作用机制.     

Anti-Cancer Activity and Phenolic Content of Extracts Derived from Cypriot Carob (Ceratonia siliqua L.) Pods Using Different Solvents

Extracts derived from the Ceratonia siliqua L. (carob) tree have been widely studied for their ability to prevent many diseases mainly due to the presence of polyphenolic compounds. In this study, we explored, for the first time, the anti-cancer properties of Cypriot carobs. We produced extracts from ripe and unripe whole carobs, pulp and seeds using solvents with different polarities. We measured the ability of the extracts to inhibit proliferation and induce apoptosis in cancer and normal immortalized breast cells, using the MTT assay, cell cycle analysis and Western Blotting. The extracts’ total polyphenol content and anti-oxidant action was evaluated using the Folin–Ciocalteu method and the DPPH assay. Finally, we used LC-MS analysis to identify and quantify polyphenols in the most effective extracts. Our results demonstrate that the anti-proliferative capacity of carob extracts varied with the stage of carob maturity and the extraction solvent. The Diethyl-ether and Ethyl acetate extracts derived from the ripe whole fruit had high Myricetin content and also displayed specific activity against cancer cells. Their mechanism of action involved caspase-dependent and independent apoptosis. Our results indicate that extracts from Cypriot carobs may have potential uses in the development of nutritional supplements and pharmaceuticals.     

Study of the metabolism of myricetin in rat urine,plasma and feces by ultra-high-performance liquid chromatography

Myricetin is a common natural flavonoid compound with various pharmacological activities. However, the metabolite characterization of this substance remains inadequate. In this study, a simple and rapid system strategy based on UHPLC-Q-Exactive Orbitrap mass spectrometry combining parallel reaction monitoring mode was established to screen and identify myricetin metabolites in rat urine, plasma and feces after oral administration. A total of 38 metabolites were fully or partially characterized based on their accurate mass, characteristic fragment ions, retention times, corresponding cLogP values, etc. These metabolites were presumed to be generated through glucuronidation, glucosylation, sulfation, dihydroxylation, acetylation, hydrogenation, hydroxylation and their composite reactions. In addition, the characteristic fragmentation pathways of flavonoids with more metabolites were summarized for the subsequent metabolite identification. The study provides an overall metabolic profile of myricetin, which would be of great help in predicting the in vivo pharmacokinetic profiles and understanding the action mechanism of this active ingredient.     

杨梅素的提取工艺研究

对杨梅树叶中杨梅素的提取有影响的有机溶剂浓度、提取温度、料液比、提取时间进行正交优化。结果表明,最佳提取工艺条件是乙醇体积分数95％,提取温度95℃,提取时间1．5h,料液比1：15,在此工艺条件下杨梅素提取率达到0．088％。     

First Chemical Synthesis of Three Natural Depsides Involved in Flavonol Catabolism and Related to Quercetinase Catalysis

We report here the first chemical synthesis of three depsides related to quercetinase‐catalyzed degradation of kaempferol, quercetin, and myricetin. The three depsides were constructed through the coupling of suitably protected phloroglucinol carboxylic acid and hydroxy‐perbenzylated, derivatives of gallic, protocatechuic, and 4‐hydroxy benzoic acids. The three synthesized target compounds proved to be identical to their natural counterparts, arising from quercetinase action on corresponding flavonols.     

Quantitative HPLC determination of main flavonoid content of <Emphasis Type="Italic">Rhododendron adamsii</Emphasis> leaves and stems

The content of main flavonoids from Rhododendron adamsii R. leaves and stems was determined quantitatively using HPLC. It was found that myricetin and quercetin dominated the identified compounds (myricetin, quercetin, dihydroquercetin, rutin) in leaves; dihydroquercetin, in stems (1.1, 1.0, and 2.5 mass% of raw material, respectively). Dihydroquercetin and rutin were found for the first time in R. adamsii. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 26–29, January–February, 2009.     

Extraction and Determination of Quercetin and Myricetin from Chamaecyparis obtusa by Ionic Liquids‐based Monolithic Cartridge

A short ionic liquids (ILs)‐based monolithic cartridge was prepared and used as the selective extraction sorbent. After the material was evaluated by field emission‐scanning electron microscopy (FE‐SEM), a new approach for the extraction and determination of quercetin and myricetin from Chamaecyparis obtusa (C. obtusa) by using ILs‐based, monolithic cartridge system was developed. Chromatographic analysis was conducted on a C₁₈ column with UV detection at 372 nm, an eluting solution consisting of acetonitrile‐water (25/75,V/V) as the mobile phase, and a flow rate of 0.7 mL·min⁻¹. A good linear relationship was demonstrated when the concentrations of quercetin and myricetin were in the range of 0.5–100.0 µg·mL⁻¹. The recoveries ranged from 101.6% to 104.6% and the inter‐ and intra‐day relative standard deviations (RSD) were less than 5.0%. This method effectively removed the impurities and avoided tedious pretreatment. It provided a fast, economic and effective method for assaying trace drugs from natural plants.