2,2’-Azobis dihydrochloride

XU z, HUA N, GODBER s (2001) Antioxidant activity of tocopherols, tocotrienols, and y-oryzanol components from rice bran against cholesterol oxidation accelerated by 2, 2 -azobis(2-methylpropionamidine) dihydrochloride. J Agri Food Chem, 49 2077-81. 

Tamai, H., Levin, S. and Gaginella, T.S. (1992). Induction of colitis in rats by 2-2 -azobis(2-amidinopropane) dihydrochloride. Inflammation 16, 69-81. 

This assay measures the ability of antioxidant components in test materials to inhibit the decline in (3-phycoerythrin ((3-PE) fluorescence that is induced by 2,2 -azobis(2-amidinopropane) dihydrochloride (AAPH) as peroxyl radical generator (ORACroo.X H202-Cu2+ as hydroxyl radical generator (ORACho.X and Cu2+ as a transition metal oxidant (ORACcu)-... 

The most popular thermal initiator is 2, 2 -azobisisobutyronitrile (AIBN), with a half-life (ti/2) of 1 h at 81 °C and 10 h at 65 °C in toluene [8,21]. Generally, 5-10 mol% of initiator is added either all in one portion or by slow addition over a period of time. There are other azo compounds which can be chosen, depending on the reaction conditions. Indeed, the nature of the substituent play an important role as can be seen for 2, 2 -azobis-(4-methoxy)-3,4-dimethyl-valeronitrile (AMVN), with a ti/2 of 1 h at 56 °C and 10 h at 33 °C in toluene. There are also hydrophilic azo compounds, such as 2, 2 -azobis-(2-methylpropionamidine) dihydrochloride (APPH), with a ti/2 of 10 h at 56 °C in water. 

The initiators used in emulsion polymerization are water-soluble initiators such as potassium or ammonium persulfate, hydrogen peroxide, and 2,2 -azobis(2-amidinopropane) dihydrochloride. Partially water-soluble peroxides such a succinic acid peroxide and f-butyl hydroperoxide and azo compounds such as 4,4 -azobis(4-cyanopentanoic acid) have also been used. Redox systems such as persulfate with ferrous ion (Eq. 3-38a) are commonly used. Redox systems are advantageous in yielding desirable initiation rates at temperatures below 50°C. Other useful redox systems include cumyl hydroperoxide or hydrogen peroxide with ferrous, sulfite, or bisulfite ion. 

An initiator solution is prepared by dissolving 0.625 g of 2,2-azobis(2-aminopropene) dihydrochloride in 6 ml water.The solution is transferred under argon into a syringe. 

Because the size of the emulsion droplets dictates the diameter of the resulting capsules, it is possible to use miniemulsions to make nanocapsules. To cite a recent example, Carlos Co and his group developed relatively monodisperse 200-nm capsules by interfacial free-radical polymerization (Scott et al. 2005). Dibutyl maleate in hexadecane was dispersed in a miniemulsion of poly(ethylene glycol)-1000 (PEG-1000) divinyl ether in an aqueous phase. They generated the miniemulsion by sonication and used an interfacially active initiator, 2,2 -azobis(A-octyl-2-methyl-propionamidine) dihydrochloride, to initiate the reaction, coupled with UV irradiation. 

The ORAC method was first proposed by Cao and co-workers in 1993. Like in the TRAP method, they used a fluorescent indicator. Determination of antioxidant activity by this method is based on measurement of decreasing fluorescence of the indicator caused by the radicals generated in the system. The reaction mixture in their proposal consisted of a fluorescent indicator p-phycoerythrin (p-PE), 2,2 -azobis(2-amidinopropane) dihydrochloride (AAPH) as a peroxyl radical generator and the analysed sample [42]. Attributing the low purity of p-phycoerythrin (approx. 30%) to the low reproducibility of fluorescence and the occurrence of different forms of phycoerythrin, Ou and co-workers [43] modified the method by replacing the indicator with fluorescein (3, 6 -dihydroxyspiro[isobenzofuran-l[3H],9 [9H]-xanthen]-3-one). 

The step 1 product (1.0 g) was dissolved in 2.0 ml toluene and then treated with dial-lyldimethylammonium chloride (1.0 g) dissolved in 4.0 ml of toluene containing 2,2 -azobis(2-amidinopropane) dihydrochloride (51 mg). The mixture was then sparged with nitrogen for 30 minutes and then stirred at 70°C for 24 hours. The solution was then cooled and precipitated with acetone and the product isolated. 

INITIATORS-FREE-RADICALINITIATORS](Vol 14) 2,2y-Azobis[2-amidinopropane] dihydrochloride [2997-92-4]... 

Joshi G, Perluigi M, Sultana R, Agrippino R, Calabrese V, Butterfield DA. 2006. In vivo protection of synaptosomes by ferulic acid ethyl ester (FAEE) from oxidative stress mediated by 2,2-azobis(2-amidino-propane)dihydrochloride (AAPH) or Fe(2 +)/ H(2jO(2) Insight into mechanisms of neuroprotection and relevance to oxidative stress-related neurodegenerative disorders. Neurochem Int 48 318-327. 

Azo compounds such as the water-soluble 2,2 -azobis(2-methylpropionamidine) dihydrochloride slowly decompose at elevated temperatures (Table 2.5) already at 40 °C, thereby yielding molecular nitrogen and two radicals [reaction (56)] (Niki 1990 Paul et al. 2000). These are first formed within the solvent cage, where about half of them recombines [reaction (57)]. The other half escapes the cage, and in the presence of 02 these radicals are converted into the corresponding peroxyl radicals [reactions (58) and (59)]. 

Total radical trapping parameter (TRAP) assay is widely used in investigations and has various modifications [45-48]. This method presumes antioxidants capability to react with peroxyl radical 2.2-azobis (2-amidinopropane) dihydrochloride (AAPH). TRAP modifications differ in methods of registering analytical signal. Most often the final stage of analysis include peroxyl radical AAPH reaction with luminescent (luminol), fluorescent (dichlorofluorescein-diace-tate, DCFH-DA) or other optically active substrate. Trolox is often used as a standard. 

As preliminary examples, AIBN was reported to give a 48 hr degradation of tetrazepam very similar to that obtained in 6 months accelerated degradation of tablets (28). Similarly, the water-soluble initiator 2,2 -azobis (2-amidinopropane) dihydrochloride was shown to accelerate the natural degradation of thymidine. In contrast, systems producing the more reactive hydroxy radicals (e.g., Fenton conditions) give mainly nonnatural degradation products (29). 

L14. Liegeois, C., Lermusieau, G., and Collin, S., Measuring antioxidant efficiency of wort, malt, and hops against the 2,2 -azobis(2-amidinopropane) dihydrochloride-induced oxidation of an aqueous dispersion of linoleic acid. J. Agric. Food Chem. 48, 1129-1134 (2000). 

FIGURE 5.13 Left low MWCO membrane (deionized water 2-methoxyethanol = 3.7 1). Right high MWCO membrane (deionized water 2-methoxyethanol = 0.34 1). The post diameter is 50 pm. For phase-separation polymerization, the monomer is 2-(N-3-sulfo-propyl-N,N-dimethylammonium) ethyl methacrylate, the cross-tinker is methylene bisacry-lamide, and the plotoinitiator is 2,2 -azobis(2-methylpropanimidamide dihydrochloride). To prevent unwanted polymerization that may occur by heat and molecular diffusion outside the UV-irradiated region, a polymerization inhibitor, hydroquinone, is also added. To facilitate covalent attachment of the porous membrane to the silica surface, it is first coated with 3-(trimethoxysilyl)propylacrylate [347]. Reprinted with permission from the American Chemical Society. 

Amino-terminated telechelic polybutadiene was prepared by LiAlH4 reduction of amidino end-group in polybutadiene, which was polymerised by a water-soluble initiator, 2,2 -azobis(amidinopropane)dihydrochloride. The structure was analysed by 1H- and 13C-NMR, but functionality of 2.0 was obtained by a titration method [70]. Synthesis of co-epoxy-functionalised polyisoprene was carried out by the reaction of 2-bromoethyloxirane with living polymer that was initiated with sec-butyl lithium. The functionality of the resulting polyisoprene was 1.04 by 1H-NMR and 1.00 by thin layer chromatography detected with flame ionisation detection [71]. 

SCHEME 11.1 Native chemical ligation and a concept using amino acid having thiol at the (i position. Acm, acetamidomethyl PG, protecting group VA-044,1,2 - azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride. 

Radicals generated during peroxidation of lipids and proteins show reactivity similar to that of the hydroxyl radical however, their oxidative potentials are lower. It is assumed that the reactive alkoxyl radicals rather than the peroxyl radicals play a part in protein fragmentation secondary to lipid peroxidation process, or protein exposure to organic hydroperoxides (DIO). Reaction of lipid radicals produces protein-lipid covalent bonds and dityrosyl cross-links. Such cross-links were, for example, found in dimerization of Ca2+-ATPase from skeletal muscle sarcoplasmic reticulum. The reaction was carried out in vitro by treatment of sarcoplasmic reticulum membranes with an azo-initiator, 2,2/-azobis(2-amidinopropane) dihydrochloride (AAPH), which generated peroxyl and alkoxyl radicals (V9). 

The antioxidant activity of anthocyanins in the fruits and leaves from different cultivars of the thornless blackberry (Rubus sp.), red raspberry (Rubus idaeus L.), black raspberry (Rubus occidentalis L.) and strawberry (Fragaria x ananassa D.) was reported [54]. Studies on the ability of endothelial cells (EC) to incorporate anthocyanins and on the potential benefits against various oxidative stressors showed that the enrichment of EC with elderberry anthocyanins gave significant protective effects in the endothelial cells against the oxidative stressors, hydrogen peroxide, 2,2/-azobis(2-amidinopropane) dihydrochloride, and iron(II) sulfate/ascorbic acid [55]. 

The Step 1 product was packed into a 4.6 x 100 mm high-pressure liquid chromatography column and treated with l.OM acrolein and 0.025M 2,2 -azobis(2-methyl-propioniamidine) dihydrochloride dissolved in water. This mixture was injected into the column, and both ends of the column were plugged. The column was then immersed in a 78°C water bath for 2 hours to complete the reaction. 

Jin and collaborators reported the antioxidant activity of cleomiscosins A (9) and C (7), isolated from the leaves and twigs of Acer okamotoatum (19). Compound 7 inhibited LDL oxidation mediated by either catalytic copper ions or free radicals generated with 2,2 -azobis(2-amidinopropane) dihydrochloride, in a dose-dependent manner. By means of electrophoretic analysis it was also observed that 7 protected apolipoprotein B-lOO against Cu fragmentation. Also, fluorescence analysis clearly indicated that both 7 and 9 protect against the oxidative modification of apoB-100, induced by either Cu + or HOCl. Compounds 7 and 9 could, therefore, be beneficial in preventing LDL oxidation in atherosclerotic lesions. 

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