Neue Antioxidantien und ihre Eigenschaften

New Antioxidants and Their Properties Compounds of the 1,2,3,4-tetrahydroxanthone series and the 3,4-cyclohexenyl cumarine series, all having antioxidative properties, were prepared by reacting the ethyl ester of cyclohexanone-2-carboxylic acid and the diethyl ester of 1,4-cyclohexanedione-2,5-dicarboxylic acid with polyvalent phenols. The fat-solubility and a certain watersolubility of these compounds were achieved by the introduction of a carboxyl group. Autoxidation tests using atmospheric oxygen were carried out mainly on unsaturated fatty acids and their esters at various temperatures. Among the substances studied the o-dihydroxy compounds showed inhibitor action for long periods at low temperatures, whereas the p-dihydroxy compounds had a maximum inhibiting action towards atmospheric oxygen only at high temperatures.     

Einfluß von Licht und Tocopherolgehalt auf die Oxidationsstabilität von Fettsäuremethylestern

Influence of light and contents of tocopherols on the oxidative stability of fatty acid methyl esters The oxidative stability of different plant oil based fatty acid methyl esters can be estimated by determining the induction period with the active oxygen method. Measuring the volatile and oil soluble acids for a long period preceding the induction period shows that the values are approaching a certain limit. Even if the esters do not differ dramatically in the composition of fatty acids it is a fact that the different production processes influence the amount of tocopherols significantly. The exclusion of light is more crucial than the exclusion of air when storing plant oil based fatty acid esters.     

Pro- und Antioxydantien auf dem Fettgebiet XXIII: Blütenfarbstoffe von Helichrysum bracteatum

Pro- and Antioxidants in the Field of Fats XXIII: Colouring Matter of the Blossoms of Helichrysum bracteatum From the viewpoint of the influence of three anthochlores, namely bractein, chalkonglucoside A and B as well as cyanin, contained in the petals of differently coloured Helichrysum bracteatum varieties, on the fading out of these flowers, the antioxidative properties of the former towards methyl linoleate were investigated. The three anthochlores possessed antioxidative action; chalkonglucoside being the strongest. The cyanin from the violet variety of immortelle did not possess any antioxidative action under the experimental conditions employed. A relationship between the occurence of flavones and the colour stability as well as inhibition of anthochlores of the Helichrysum bracteatum prior to autoxidation was established. Isosalipurposide, a third chalkonglucoside, could be detected in the covering leaves of the yellow variety of Helichrysum bracteatum with the help of paper and thin-layer chromatography.     

X-Ray Opaque Methacrylate Polymers for Biomedical Applications

The synthesis of a number of halogenated aromatic methacrylate monomers was achieved by (1) the esterification of hydroxyl-containing methacrylate esters with 2,3,5-tri-iodobenzoic acid and (2) by the nucleophilic addition of 2,3,5-tri-iodobenzoic acid, or polyhalogenated phenols, to 2,3-epoxypropyl methacrylate, yielding white crystalline products which were fully characterized. These monomers could be homopolymerized in the melt to produce clear, intensely X-ray opaque glasses possessing high refractive indices. The monomers themselves were soluble in a variety of methacrylate monomers with which they could be copolymerized to produce clear radiopaque materials. The stability of the homopolymers in an aqueous environment was excellent as was thermal stability, exhibiting little decomposition below 300°C. © 1997 SCI.     

间苯二酚衍生物型苯并三唑类紫外线吸收剂的合成及性能测试

合成了6个间苯二酚衍生物型苯并三唑类紫外线吸收剂（Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ、Ⅵ）,反应收率分别为85.7％、83.5％、81.7％、82.5％、82.7％和81.5％.通过紫外吸收光谱分析,该6个化合物在270～400 nm均有较高的摩尔消光系数,是传统烷基酚衍生物类紫外线吸收剂的1.7倍以上.经光老化测试,其光稳定性较好,当人工加速光老化12 h后,该6个化合物碎裂18.03％～23.85％,而传统烷基酚的衍生物类紫外线吸收剂则碎裂27.16％.实验证明该类间苯二酚衍生物型苯并三唑紫外线吸收剂是一类高效光稳定剂.     

Natürliche Antioxidantien III Zur Kinetik der antioxidativen Wirkung von α-Tocotrienol

Natural Antioxidants III: Kinetics of Antioxidative Action of α-Tocopherols Kinetics of antioxidative action of α-tocotrienol was compared to that of other tocopherols. Specially purified methyl esters of total fatty acids of sunflower oil served as substrates, whose first ?stable”? autoxidation product is linoleic acid hydroperoxide. In all reactions studied, α-tocotrienol was somewhat more effective than α-tocopherol. The maximum inhibition was reached at a concentration of 0.02%. With increasing concentration, the well known phenomenon of reversion occurs with α-tocotrienol to a greater degree than with α-tocopherol. α-Tocotrienol, added in an amount of 0.12%, causes a more rapid decomposition of peroxides than α-tocopherol.     

Natürliche Antioxidantien IV. Antioxidantien des fetten Öles von Foeniculum vulgare Miller, 2. Mitt.

Natural Antioxidants IV: Antioxidants in the Fatty Oil of Foeniculum vulgare Miller, 2. Communication Further natural antioxidants were found in the fatty oil of fennel fruits (Foeniculum vulgare, Mill.) which is highly resistant to autoxidation. Chemical and mass spectrometric examination revealed the structures of phytosteryl-ß-fructofuranosides and their fatty acid esters, 7-hydroxy- and 6,7-dihydroxy-cumarin, as well as oleanolic acid, that is active as an antioxidant. Gas chromatography showed the presence of sitosterol, stigmasterol, Δ⁷-stigmastenol, campesterol, cholesterol, Δ⁷-campestenol, Δ⁵-avenasterol, as well as campestadienol and stigmastadienol in the steryl glycosides.     

Effects of emulsifiers on the oxidative stability of soybean oil TAG in emulsions

The effects of two types of commercial emulsifiers, sucrose FA esters and polyglycerol FA esters, on the oxidation of soybean oil TAG-in-water emulsions were studied. Both emulsifiers influenced the oxidative stability of soybean oil TAG in the emulsion, but they had little effect on the oxidation of TAG in bulk phase. When the TAG were dispersed with sucrose esters having the same FA composition, the oxidative stability increased as their hydrophilic-lipophilic balance (HLB) increased. On the other hand, when the HLB was the same, the oxidative stability increased with increasing acyl chain length of the FA esterified on sucrose ester. However, the effect of the polyglycerol ester could not be explained by the relationship with HLB or the acyl composition. When the stability of TAG in emulsion was compared under the same concentrations of TAG, emulsifier, and oxidation inducer, the TAG dispersed with sucrose esters were oxidatively less stable than with polyglycerol esters. Analysis of the emulsion droplet size suggested that the lower oxidative stability of TAG dispersed with sucrose esters was partly due to their relatively smaller droplet sizes.     

Pro- und Antioxydantien auf dem Fettgebiet XX: Die Lipoide der Hefezellen in verschiedenen Wachstumsphasen

Pro- and Antioxidants in The Field of Fats XX: Lipids of the Yeast Cells in Different Stages to Growth By the example of different cultures of saccharomyces cerevisiae it is shown that the amount of lipids of the same and their composition depend on the age and the growth of the yeast cells. Under anaerobic conditions, the lipids of different classes are diminished and they are converted to physiologically less active compounds e. g. sterols into squalene. The presence of oxygen is necessary for the biosynthesis of phospholipids and sterol esters also.     

The Inhibitory Effect of Gallic Acid Alkyl Esters on Lipid Oxidation of Intactly Soaked Oyster Meats and Oyster Meat Homogenates during Refrigerated Storage

In this study, the antioxidant effects of gallic acid (GA) and its alkyl esters including methyl gallate (MG), butyl gallate (BG), octyl gallate (OG), and lauryl gallate (LG) in whole oyster meats and oyster meat homogenates during cold storage are investigated. The oxidation degree of lipid is measured by peroxide value (POV), thiobarbituric acid active substances (TBARS), and polyunsaturated fatty acid (PUFA) percentage. The results show that the lipid oxidation in the two types of samples is inhibited by GA alkyl esters, and the antioxidant effects first increase and then decrease along with the extension of the chain length, among the esters, BG and OG are relatively more effective. Therefore, it is speculated that the antioxidant capacity of GA alkyl esters may be influenced by hydrophobicity and follows a “cut-off effect” in whole oyster meats and oyster meat homogenates. Practical application: Seafood is easily oxidized even under cold storage because it contains more PUFA. Antioxidants are widely used to inhibit lipid oxidation. In this study, the antioxidant capacity of GA alkyl esters in whole oyster meats and oyster meat homogenates is investigated, which improves the selection of suitable antioxidants to strengthen the oxidation stability of oyster samples for cold storage.     

Pro- und Antioxydantien auf dem Fettgebiet XXI: Phenolische Verbindungen pflanzlichen Ursprungs

Pro- and Antioxidants in the Field of Fats XXI: Phenolic Compounds of the Vegetable Origin Quercetin, dihydroquercetin, robinetin, rhamnetin, morin, fisetin and rutin were investigated for their antioxidative effect in relation to their concentration in the methyl esters of linoleic acid and linseed oil fatty acids and linseed oil fatty acids as well as on soyabean oil and linseed oil. It is found that the investigated flavonols act as antioxidants. The effect is dependent on the concentration. The inversion effect due to increase in concentration could not be observed under the experimental conditions. The relation between the antioxidative effect and the chemical constitution of flavonols is discussed.     

Pro- und Antioxydantien auf dem Fettgebiet XXVI: Anthochlore von Dahlia variabilis und Cosmos sulphureus

Pro- and Antioxidants in the Field of Fats XXVI: Anthochlores of Dahlia variabilis and Cosmos sulphureus The authors have determined the antioxidative activity of the anthochlor pigments of Dahlia variabilis and Cosmos sulphureus on methyl linoleate. It was found that the aglycones butein and sulphuretin exhibit stronger antioxidative action than the chalkone aglycone 2″,4,4″-trihydroxy chalcone. During the treatment of the two flowers, a splitting of the glycosides was observed. In the freshly cut Cosmos sulphureus variety no aglycones could be detected. Furthermore, the distribution of anthochlores in the various series of petals in Dahlia variabilis and Helichrysum bracteatum was studied.     

Untersuchungen des Reaktionsverlaufes und der Produkte der säurekatalysierten Reaktion von Phenolen mit Holzöl, 2. Vergleichende untersuchungen an verschiedenen phenolen

In this paper the acid-catalysed reaction between phenols and tung oil is investigated for 4 different phenols (phenol, o-, m- and p-cresol). This reaction is important for the production of modified resins for electrical insulating laminates. In particular by means of ¹³C-NMR- and IR-method it is proved that phenols are C-alkylated by tung oil in the manner of a Friedel-Crafts-reaction exceptionally. The reaction positions at the phenols are determined. Further, the rates of the reaction of phenol with the eleostearic acid esters are compared for the four different phenols.     

Phenolische Pflanzeninhaltsstoffe als natürliche Antioxidantien

Plant Phenolics as Naturally Occurring Antioxidants Phenolic compounds largely occuring in nature such as flavonols, flavones, hydroxybenzoic acids and hydroxycinnamic acids and their esters have antioxydative properties, which can be considerable in some cases. The antioxydative properties of vegetables and spices may often depend on plant phenolics. Further on the protective effect of flavonoids on ascorbic acid is reviewed.     

Einfluß von Schwefelverbindungen auf die Inhibition der Thermooxidation von Polypropylen

The influence of mixtures of substituted phenols with sulphur compounds on the thermooxidative stability of polypropylene was studied. Following substituted phenols were used: 4,4′-butylidene-bis(3-methyl-6-tert.-butylphenol), 2,2′-methylidene-bis(4-methyl-6-tert.-butylphenol) and 4,4′-thio-bis(3-methyl-6-tert.-butylphenol). As sulphur compounds phenylalkylsulphides, p-nitrophenylalkylsulphides and some other p-substituted phenylsulphides were used. The effect of these mixtures was studied at 180°C in oxygen atmosphere.     

Photo‐degradation of hydrophobic esters of pyridinecarboxylic acids as copper extractants from chloride media and their copper complexes

The photo‐stability of hydrophobic esters of pyridine‐3‐carboxylic acid and pyridine‐3,5‐dicarboxylic acid containing 2‐ethylhexyl‐, octyl‐, and dodecyl‐substituents which are model extractants of copper from chloride media were studied together with the photo‐degradation of their copper complexes. The results indicate that UV light degraded the esters of both pyridine‐3,5‐dicarboxylic acid and pyridine‐3‐carboxylic acid. The degree of degradation depended on the structure of the ester, the type of solvent, and the presence of oxygen, water or hydrochloric acid in the solution during exposure to visible or UV‐visible light. Photo‐reactions between the solvent and the esters were also observed. Copper has a considerable influence on the photo‐stability of the esters. Copyright © 2005 Society of Chemical Industry     

Organophosphorus antioxidants action mechanisms and new trends

Phosphite and phosphonite esters can act as antioxidants by three basic mechanisms depending on their structure, the nature of the substrate to be stabilized and the reaction conditions. All phosph(on)ites are hydroperoxide-decomposing secondary antioxidants. Their efficiency in hydroperoxide reduction decreases in the order phosphonites > alkylphosphites > arylphosphites > hindered arylphosphites. Five-membered cyclic phosphites are capable of decomposing hydroperoxides catalytically due to the formation of acidic hydrogen phosphates by hydrolysis and peroxidolysis in the course of reaction. Hindered aryl phosphites can act as chain-breaking primary antioxidants being substituted by alkoxyl radicals and releasing hindered aryloxyl radicals which terminate the radical chain oxidation. At ambient temperatures, the chain-breaking antioxidant activity of aryl phosphites is lower than that of hindered phenols, because the rate of their reaction with peroxyl radicals and their stoichiometric inhibition factors are lower than those of phenols. In oxidizing media at medium temperatures, however, hydrolysis of aryl phosph(on)ites takes place giving hydrogen phosph(on)ites and phenols which are effective chain-breaking antioxidants. 2,2,6,6-Tetramethyl- and 1,2,2,6,6-Pentamethylpiperidinyl phosphites and phosphonites (HALS-phosph(on)ites) surpass many common phosphites, phenols and HALS compounds as stabilizers in the thermo- and photo-oxidation of polymers. Their superior efficiency is probably due to an intramolecular synergistic action of the HALS and the phosph(on)ite moieties of their molecules.     

Stabilization of polypropylene

Antioxidants and UV absorbers are vital to the commercialization of polypropylene because of their influence on this polymer's light stability, heat or oxidative stability, processing stability, and gas fading due to nitrogen oxides. The effects of these stabilizers are measured in terms of polypropylene's initial color, color retention, and retention of physical properties when the polymer is exposed to direct weathering and to elevated temperatures. The relative washfastness or resistance to extraction by aqueous systems under various laundering conditions is another important, measurable property of UV absorbers and antioxidants in polypropylene. Such measurements are usually made using stabilized polypropylene molded plaques and monofilaments containing UV absorbers, antioxidants and, often, combinations of the two.     

Anwendung von Antioxydantien zur Verlängerung der Lagerung von Shortenings II: Studium flüchtiger Autoxydationsprodukte

Use of Antioxidants in the Storage of Shortenings II: Studies on Volatile Products of Autoxidation The changes during storage in the content of volatile products of autoxidation in shortenings containing antioxidant were investigated. In the shortenings containing ascorbyl palmitate, the least amount of unsaturated and saturated aldehydes were found. During storae in the laboratory, the stability of shortenings having 0.2% ascorbyl palmitate was 6 times higher, and those of shortenings containing 0.02% butyl hydroxyanisole or 0.01% propyl gallate 3 to 4 times higher than the samples stored without antioxidants.     

Quantification of carbonyls produced by the decomposition of hydroperoxides

Carbonyls produced by the decomposition of cyclohexene hydroperoxide and various hydroperoxides of linoleic and linolenic acids and their methyl esters were determined by gas chromatography of the 2,4,6-trichlorophenylhydrazones. The effect of temperature, iron and copper ions, ethanol and several antioxidants on the rate of decomposition, the nature of the products and their yield was observed. The hydroperoxides of methyl esters decomposed more slowly than those of free fatty acids. Ethanol slowed, and metal ions accelerated the rates of decomposition. Metal ions, especially copper, increased the yield and complexity of the carbonyls formed, but ethanol decreased carbonyl yields. Antioxidants and decomposition temperatures changed the relative yields of carbonyls produced. The 9- and 13-hydroperoxides of linoleic acid gave similar carbonyls, but those of linolenic acid did not. The carbonyl mixtures produced from autoxidized fatty acid methyl esters were more complex than those produced from lipoxygenase-treated fatty acids.