Study on the Photodegradation of Salicylic Acid in Different Vehicles in the Absence and in the Presence of TiO2

In this work, the direct photolysis of salicylic acid, generally used as keratolytic agent in many dermatological products and as preservative in cosmetics, was investigated. The photodegradation of the acid under UVB irradiation was evaluated in different vehicles, such as water solutions at different pH, propylene glycol/water, and ethanol/water mixtures, sodium dodecyl sulphate solutions, and O/W emulsions prepared with Montanov 68 and Amphysol K as emulsifiers. The increase of pH enhanced the photodegradation of salicylic acid while the different vehicles protected the acid from the action of UVB radiations. However, the best protection was observed dissolving the acid in the lipid core of O/W emulsions, which probably removes the active from the polar environment that can promote the photolysis. The photocatalytic activity of TiO₂ on the degradation of salicylic acid also was evaluated. TiO₂ frequently is used as sunscreen in many cosmetic preparations. Salicylic acid and the pigment can be contained in the same solar formulation; hence, it can be interesting to study their interaction under UVB. TiO₂ enhanced the photodegradation of salicylic acid in all the media previously reported and its photocatalytic activity was influenced by the pH and by the components of the vehicles.     

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.     

Effect of Propylene Glycol and Ethanol on the UVB-Induced Peroxidation of Linoleic Acid and Lipids of Porcine Skin,in the Presence of Different TiO2 Specimens

Titanium dioxide is a sunscreen pigment with photocatalytic activity. We studied the behavior of different TiO₂ specimens used in cosmetic products on the UVB-induced peroxidation of linoleic acid as model substrate and of porcine skin, at different pH values. Lipoperoxidation of linoleic acid occurred to a lower extent with the coated compared to the uncoated TiO₂, and it decreased at pH 7.0 compared to 4.0. The addition of organic additives such as propylene glycol and ethanol induced a significant reduction of the lipoperoxidation activity, particularly with the most reactive TiO₂ specimens. Similar results were obtained with the porcine skin.     

水溶性纳米Fe3O4-阿魏酸抗凝血材料的合成及性能

为提高具抗凝血性能的阿魏酸分子在水中的溶解性进而提高其药效,利用DBI(3,4-二羟基苯甲醛)、PEG(聚乙二醇4000)和纳米Fe₃O₄,采用接枝的方法制备了水溶性纳米Fe₃O₄-DBI-PEG-阿魏酸抗凝血杂化材料,用IR、¹H NMR、TG、SEM、TEM、VSM和粒度测试方法表征了产物。结果表明阿魏酸(FA)接枝在了经过DBI-PEG活化后的纳米Fe₃O₄氧化物表面。杂化材料具有良好的水溶性(溶解度大于10 mg·mL^-1)和顺磁性。抗凝血试验表明相同条件下杂化材料的抗凝血时间和复钙时间比阿魏酸要长,杂化材料的活化部分凝血活酶时间(APTT)和凝血酶原时间(PT)比空白组要长,杂化材料的抗凝血时间随浓度的增大而延长。     

水溶性纳米Fe3O4-阿魏酸抗凝血材料的合成及性能

为提高具抗凝血性能的阿魏酸分子在水中的溶解性进而提高其药效,利用DBI(3,4-二羟基苯甲醛)、PEG(聚乙二醇4000)和纳米Fe₃O₄,采用接枝的方法制备了水溶性纳米Fe₃O₄-DBI-PEG-阿魏酸抗凝血杂化材料,用IR、¹H NMR、TG、SEM、TEM、VSM和粒度测试方法表征了产物。结果表明阿魏酸(FA)接枝在了经过DBI-PEG活化后的纳米Fe₃O₄氧化物表面。杂化材料具有良好的水溶性(溶解度大于10 mg·mL^-1)和顺磁性。抗凝血试验表明相同条件下杂化材料的抗凝血时间和复钙时间比阿魏酸要长,杂化材料的活化部分凝血活酶时间(APTT)和凝血酶原时间(PT)比空白组要长,杂化材料的抗凝血时间随浓度的增大而延长。     

Photodegradation of Caffeic Acid in W/O/W Emulsions in the Absence and in the Presence of TiO2

Caffeic acid, a natural phenol with antioxidant and sunscreen activity, can undergo photooxidation upon UV irradiation. The photodegradation of caffeic acid at different concentrations was assessed in water, at pH 4.0 and 6.0, without and with TiO₂. The study was then carried out on W/O/W emulsions entrapping the phenolic acid either in the inner or in the outer aqueous phase in the absence and in the presence of TiO₂, added in the external phase (pH 6.0 or 7.0). The degradation of caffeic acid followed a pseudo-zero order kinetic with an inverse dependence from its initial concentration; at increasing pH of the medium caffeic acid degraded faster. The addition of TiO₂ increased the initial photodegradation rate. Compared with water, W/O/W emulsions protected the phenol towards both the photodegradation and the photocatalytic activity of TiO₂. Multiple systems allowed to incorporate caffeic acid and TiO₂ in the same formulation avoiding any catalytic interactions.     

Ag@AgI等离子体负载TiO2酸蚀纳米带的制备及可见光光催化性能的研究

采用沉积-沉淀法将AgI分散到TiO2酸蚀纳米带上,然后通过光照进而分解出Ag颗粒,最终获得了Ag@AgI等离子体负载的TiO2酸蚀纳米带(AIST)。利用UV-Vis吸收光谱、XRD、SEM对产物进行表征,并研究了可见光下对甲基橙(MO)的光催化降解性能。结果表明,纳米带酸蚀后利于AgI的沉积,Ag的表面等离子体共振效应可以增强催化剂对于可见光的吸收,使可见光下AIST的光催化降解性能显著提高。     

Application of ZnO‐Al2O3 Nanocomposite as Nanocatalyst for Photodegradation of Acid Violet 5B

ZnO‐Al₂O₃ nanocomposite (ZANC) is used as nanocatalyst for photodegradation of acid violet 5B (AV5B) as an industrial dye. The experimental data shows that the degradation of AV5B is accelerated by ZANC and UV light. The effects of various parameters such as pH, hydrogen peroxide and ethanol are investigated on the photodegradation efficiency. Photocatalytic degradation rate of AV5B is increased by ethanol and hydrogen peroxide. Based on the kinetic studies, the rate constant of the photodegradation reaction is estimated 2.829 × 10^‐1 min^‐1.     

Antioxidative effects of flavonols and their glycosides against the free-radical-induced peroxidation of linoleic acid in solution and in micelles

The antioxidative effect of flavonols and their glycosides against the peroxidation of linoleic acid has been studied in homogeneous solution (tBuOH/H(2)O, 3:2) and in sodium dodecyl sulfate and cetyl trimethylammonium bromide micelles. The peroxidation was initiated thermally by the water-soluble initiator 2,2'-azobis(2-methylpropionamidine) dihydrochloride, and the reaction kinetics were studied by monitoring the formation of linoleic acid hydroperoxides. The synergistic antioxidant effect of the flavonols with alpha-tocopherol (vitamin E) was also studied by following the decay kinetics of alpha-tocopherol and the alpha-tocopheroxyl radical. Kinetic analysis of the antioxidative process demonstrates that the flavonols are effective antioxidants in solution and in micelles, either alone or in combination with alpha-tocopherol. The antioxidative action involves trapping the initiating radicals in solution or in the bulk-water phase of the micelles, trapping the propagating lipid peroxyl radicals on the surface of the micelles, and regenerating alpha-tocopherol by reducing the alpha-tocopheroxyl radical. It was found that the antioxidant activity of the flavonols and their glycosides depends significantly on the position and number of the hydroxy groups, the oxidation potential of the molecule, and the reaction medium. The flavonols bearing ortho-dihydroxy groups possess significantly higher antioxidative activity than those without such functionalities, and the glycosides are less active than their parent aglycones. The activity of the flavonols is higher in micelles than in solution, while the activity of alpha-tocopherol is lower in micelles than in solution. This is because the predominant factor for controlling the activity is the hydrogen-bonding interaction of the antioxidant with the micellar surface in the case of hydrophilic flavonols, while it is the inter- and intramicellar diffusion in the case of lipophilic alpha-tocopherol.     

Effect of Reactive Species Photogenerated by the Ultraviolet Irradiation of TiO2 on the Peroxidation of Linoleic Acid

This article shows that hydroxyl radicals adsorbed on the surface of TiO₂ (Ti-^?OH groups) account for about 70–100% of the photocatalytic peroxidation of linoleic acid under UVB irradiation, which results into malondialdehyde production. The experimental data are silent concerning the involvement of ¹O₂ in the process, although an upper limit of 30% can be hypothesized, while an involvement of surface-bound holes into the lipoperoxidation process can be excluded.     

阿魏酸过渡金属配合物的合成及抗凝血作用研究

用阿魏酸与Fe、Co、Ni、Cu、Zn的硝酸盐制备了5种过渡金属配合物,通过红外光谱、热重-差热分析、元素分析、荧光和紫外光谱的方法对配合物进行了表征,确定了配合物的组成。并对配体和配合物进行了全血凝血时间、复钙时间、活化部分凝血活酶时间、凝血酶原时间的测定,结果表明5种配合物具有较好的抗凝血性质。通过荧光光谱、紫外光谱、圆二色谱研究了配合物与人血清白蛋白(HSA)的相互作用,HSA的荧光光谱表明配合物对其有荧光猝灭作用并使其发射峰位置红移,紫外光谱表明配合物的加入导致HSA吸收强度增加且吸收峰位置紫移,圆二色谱表明配合物的存在可引起HSA构象的变化。推测配合物抗凝血作用的起效与其和血清白蛋白之间的相互作用有一定的联系。     

Epoxidation of Polyunsaturated Fatty Acid Double Bonds by Dioxirane Reagent: Regioselectivity and Lipid Supramolecular Organization

The use of dimethyldioxirane (DMD) as the epoxidizing agent for polyunsaturated fatty acids was investigated. With fatty acid methyl esters, this is a convenient method for avoiding acidic conditions, using different solvents, and simplifying the isolation procedures, with less contamination due to by‐products. The reagent was also tested with free fatty acids in water. In this case, the supramolecular organization of fatty acids influenced the reaction outcome, and the epoxidation showed interesting regioselective features. The C?C bonds closest to the aqueous‐micelle interface is the most favored for the interaction with dimethyldioxirane. The preferential epoxidation of linoleic acid (= (9Z,12Z)‐octadeca‐9,12‐dienoic acid) to the 9,10‐monoepoxy derivative was achieved, with a high yield and 65% regioselectivity. In case of arachidonic acid (= (5Z,8Z,11Z,14Z)‐eicosa‐5,8,11,14‐tetraenoic acid) micelles, the regioselective outcome with formation of the four possible monoepoxy isomers was studied under different conditions. It resulted to be a convenient synthesis of ‘cis‐5,6‐epoxyeicosatrienoic acid’ (= 3‐[(2Z,5Z,8Z)‐tetradeca‐2,5,8‐trienyl]oxiran‐2‐butanoic acid), whereas in reverse micelles, epoxidation mostly gave ‘cis‐14,15‐epoxyeicosatrienoic acid (= (5Z,8Z,11Z)‐13‐(3‐pentyloxiran‐2‐yl)trideca‐5,8,11‐trienoic acid).     

杂多酸光催化降解有机污染物

本文综述了杂多酸对有机污染物的光催化降解,包括自身光致催化作用,半导体协同光催化作用,H₂O₂存在下的类Fenton反应和超声辅助催化作用。杂多酸与有机物反应的机理主要是电子-空穴对的产生和·OH等自由基的生成。概述了杂多酸的结构类型和杂多酸光催化作用的优点和局限性,提出利用掺杂调变杂多酸的晶体结构,降低其能带宽度,提高光催化作用反应的量子效率;探索杂多酸与其它电子受体的组合,特别是与具有可见光活性的物质的组合,以扩大光响应范围,实现可见光催化反应。     

“超浓盐酸”介质中钯微乳萃取行为

采用多种分子谱学的表征手段, 研究了萃钯有机相中由于酸的共萃导致溶液微观聚集态结构的变化. 研究结果表明, 与高酸度盐酸水溶液平衡后的TBP载钯有机相微乳水团中形成了浓度远大于常规饱和浓盐酸的“超浓盐酸”; 微乳水团内H+和Cl-的大量聚集增浓对Pd离子的络合配位状态产生影响, H+参与了Pd离子配位状态的转变; 有机相“超浓盐酸”形成后, 使得微乳水团中大量存在的H+有可能参与调控水团中各种HmPdClnz+络合离子配位状态的相对含量. 被H+活化的TBP表面活性剂与钯离子的各种配位状态的匹配程度最终决定了钯的萃取行为.     

EDTA有效促进石墨相氮化碳(g-C3N4)光催化降解甲基橙

研究了在光照下,乙二胺四乙酸（EDTA）的添加促进石墨相氮化碳（g-C₃N₄）光催化降解甲基橙（MO）.研究了H⁺和羧酸根负离子对光降解MO的影响.紫外-可见漫反射光谱（DRS）研究表明,EDTA的加入并没有改变g-C₃N₄的电子结构和光电特性.EDTA的加入捕获了空穴（h⁺）,促进了光生e^-/h⁺对的分离,从而使光降解活性提高.证明了·O₂^-是光催化降解过程中的主要活性物种.基于上述研究结果,我们提出了一种可能的EDTA促进g-C₃N₄光催化降解MO的机理.这些结果为提高g-C₃N₄光催化降解水体中有机污染物的性能提供了一种新方法.     

Influence of the Structure of Cetyltrimethylammonium Bromide Based Microemulsions on Base Hydrolysis of Carboxylic Acid Esters

The structure of water/cetyltrimethylammonium bromide/n-butanol/hexane microemulsions was studied by conductometry, viscometry, and Fourier transform ¹H NMR spectroscopy with pulse magnetic field gradient. The regions of phase inversion from inverse micelles in hexane through a bicontinual structure to a dispersion of normal micelles in water were determined. The influence of the structure of the microemulsions on the rate of hydrolysis of carboxylic acid p-nitrophenyl esters was analyzed. The hydrolysis rate constants considerably increase in going from inverse to normal microemulsions.     

Studies on bio-antioxidants--prooxidation of vitamin E on the autoxidation of linoleic acid in sodium dodecyl sulfate micelles

The reaction of vitamin E (alpha-tocopherol) with linoleic acid containing peroxidized linoleic acid has been studied. No significant reaction was found in ethanol solution, whereas in sodium dodecyl sulfate micelles vitamin E reacted rapidly with peroxidized linoleic acid, and thereby induced the peroxidation of linoleic acid, leading to oxygen absorption. The reaction kinetics was studied in detail by u.v. spectroscopy, HPLC and ESR spectroscopy. It was found that the main product was alpha-tocopherone with alpha-tocopheroxy radical as the reaction intermediate. A mechanism involving two consecutive bimolecular reactions between peroxidized linoleic acid and alpha-tocopherol and between peroxidized linoleic acid and alpha-tocopheroxy radical, with rate constant 2.93 and 6.21 mol/L-1s-1 respectively is proposed. The micellar effect on the reaction is discussed.     

Solid-phase photocatalytic degradation of polystyrene plastic with TiO2 as photocatalyst

Solid-phase photocatalytic degradation of polystyrene (PS) plastic with TiO₂ as photocatalyst was investigated in the ambient air under ultraviolet light irradiation. Higher weight loss rate, lower average molecular weight, increased carbonyl peak intensity, less volatile organics and more CO₂ emitted with irradiation in PS-TiO₂ composite sample compared to pure PS sample were observed. These facts indicated the higher photodegradation rate of PS-TiO₂ sample than that of PS sample, and emphasized the potential of the composite sample in bring about complete photodegradation of polystyrene plastic. It is implied that the degradation initially occurred over TiO₂ particles, followed by the diffusion reaction with the aid of reactive oxygen species generated on TiO₂ particle surface.     

The release of cephanone in CTAB/n-C5H11OH/H2O system

Controlled release of cephanone from hexadecyltrimethylammonium bromide (CTAB) micelles and CTAB/n-C₅H₁₁OH/H₂O microemulsions was studied. The results showed that the release rate of cephanone was reduced in CTAB micelles and CTAB/n-C₅H₁₁OH/H₂O microemulsions, because of the solubilization of cephanone in micelles and microemulsions. The release of cephanone from CTAB micelles and CTAB/n-C₅H₁₁OH/H₂O microemulsions was characterized by Fickian diffusion and non-Fickian diffusion.     

Characterization of Nitro Arachidonic Acid and Nitro Linoleic Acid by Mass Spectrometry

Nitration of arachidonic and linoleic acids was performed with nitronium tetrafluroborate, nitrogen dioxide, and dinitrogen trioxide. The nitro compounds were separated on HPLC and characterized further on mass spectrometry. Formation of nitro arachidonic acid m/z 348 and nitro linoleic acid m/z 324 were observed with all the reagents. Interestingly, MS/MS of nitro AA and nitro LA showed specific ions m/z 142, m/z 193, and m/z 206 for nitro arachidonic and m/z 156 and m/z 196 for linoleic acid that were common in all three reactions.