Methods antioxidant

Antioxidant capacities of common individual curcuminoids were determined in vitro by phosphomolybdenum and linoleic acid peroxidation methods. Antioxidant capacities expressed as ascorbic acid equivalents (pmol/g) were 3099 for curcumin, 2833 for demethoxycurcumin, and 2677 for bisdemethoxycurcumin at concentrations of 50 ppm. The same order of antioxidant activity (curcumin > demethoxycurcumin > bisdemethoxycurcumin) was observed when compared with BHT (buty-lated hydroxyl toluene) in linoleic peroxidation tests. The antioxidant activity of curcumin in the presence of ethyl linoleate was demonstrated and six reaction products were identified and structurally characterized. The mechanism proposed for this activity consisted of an oxidative coupling reaction at the 3 position of the curcumin with the lipid and a subsequent intramolecular Diels-Alder reaction. ... 

Antimutagenic activity. Ethanol (70%) extract of the dried aerial parts, on agar plate, was inactive on Escherichia coli PQ37 vs mitomycin-induced mutagenesis, assessed by the SOS-chromotest method Antioxidant activity. Hexane and methanol extracts of the dried seed, tested on lard at a concentration of 0.06 %, were inactive Seed oil, at undiluted concentration, was active " . Acetone extract of the seed, at a concentration of 0.2 mg/kg, was active. Linoleic acid was used as a substrate in this test " . 

To promote ionic addition of HBr air must be excluded and the unsaturated compound and the solvent must be tested for peroxide which, if present, must be removed by some suitable method. Antioxidants, such as diphenylamine, thiophenol, or thiocresol, may be added, since they neutralize the effect of small amounts of peroxide.185... 

AOAC method Antioxidant Food Anaiyticai technique... 

Antioxidant methods Antioxidant trends (total phenol in jUg/ml)... 

Figure 3. Antioxidant activity of aldehyde-modified HSA against hypochlorous acid (HOCl). One milliliter solution contained 10 /llM HOCl, 250 juM DTP A, 500 fiM luminol and 10 nM of aldehyde-modifed HSA. Chemiluminescent intensity was recorded as described MATERIALS AND METHODS. Antioxidant activities of aldehyde-modified HSA against HOCl were shown as Vo of native HSA.

Lactic acid and - acetic acid lower the pH and can inhibit the growth of bacteria especially. Full efficiency is mostly given by a combination of several preservatives and physical methods. Antioxidants ... 

Processing. SAN copolymers may be processed using the conventional fabrication methods of extmsion, blow mol ding, injection molding, thermoforming, and casting. Small amounts of additives, such as antioxidants, lubricants, and colorants, may also be used. Typical temperature profiles for injection mol ding and extmsion of predried SAN resins are as follows (101). 

Antioxidants have been shown to improve oxidative stabiHty substantially (36,37). The use of mbber-bound stabilizers to permit concentration of the additive in the mbber phase has been reported (38—40). The partitioning behavior of various conventional stabilizers between the mbber and thermoplastic phases in model ABS systems has been described and shown to correlate with solubiHty parameter values (41). Pigments can adversely affect oxidative stabiHty (32). Test methods for assessing thermal oxidative stabiHty include oxygen absorption (31,32,42), thermal analysis (43,44), oven aging (34,45,46), and chemiluminescence (47,48). 

Long-chain esters of pentaerythritol have been prepared by a variety of methods. The tetranonanoate is made by treatment of methyl nonanoate [7289-51-2] and pentaerythritol at elevated temperatures using sodium phenoxide alone, or titanium tetrapropoxide in xylene (12). PhenoHc esters having good antioxidant activity have been synthesized by reaction of phenols or long-chain aUphatic acids and pentaerythritol or trimethyl olpropane (13). 

Excellent correlation was found when results at 660 nm and 749 nm were compared using a reference hexokinase glucose method (27). The dose response was excellent up to 300 mg/dL glucose. In general, water-borne coatings do not lend themselves to ranging by antioxidants (qv). 

CPA. Copolymer alloy membranes (CPAs) are made by alloying high molecular weight polymeries, plasticizers, special stabilizers, biocides, and antioxidants with poly(vinyl chloride) (PVC). The membrane is typically reinforced with polyester and comes in finished thicknesses of 0.75—1.5 mm and widths of 1.5—1.8 m. The primary installation method is mechanically fastened, but some fully adhered systems are also possible. The CPA membranes can exhibit long-term flexibiHty by alleviating migration of the polymeric plasticizers, and are chemically resistant and compatible with many oils and greases, animal fats, asphalt, and coal-tar pitch. The physical characteristics of a CPA membrane have been described (15). 

In general, one day of oven aging at 70°C corresponds to one year of natural or shelf aging (a minimum requirement for mbber products), whereas the oxygen and air bomb methods are more drastic. By varyiag the amounts and types or combiaations of antioxidants the relative effectiveness of these materials against normal oxygen deterioration can be determined. 

The effectiveness of antioxidants as preservatives for fats and oils is evaluated by determining the rate of peroxide development using the Active Oxygen Method (AOM) (29). The development of a rancid odor is used to evaluate the stabiUty of food items (Schaal Oven StabiUty test) (30). 

AGE-Gontaining Elastomers. The manufacturing process for ECH—AGE, ECH—EO—AGE, ECH—PO—AGE, and PO—AGE is similar to that described for the ECH and ECH—EO elastomers. Solution polymerization is carried out in aromatic solvents. Slurry systems have been reported for PO—AGE (39,40). When monomer reactivity ratios are compared, AGE (and PO) are approximately 1.5 times more reactive than ECH. Since ECH is slightly less reactive than PO and AGE and considerably less reactive than EO, background monomer concentration must be controlled in ECH—AGE, ECH—EO—AGE, and ECH—PO—AGE synthesis in order to obtain a uniform product of the desired monomer composition. This is not necessary for the PO—AGE elastomer, as a copolymer of the same composition as the monomer charge is produced. AGE content of all these polymers is fairly low, less than 10%. Methods of molecular weight control, antioxidant addition, and product work-up are similar to those used for the ECH polymers described. 

The present method is applicable with slight modifications to the preparation of both the ortho and para aminonaphthols and to many homologues, benzologues, and heterocyclic isologues of these substances. The chief feature of novelty is in the use of stannous chloride as an antioxidant in preparing and crystallizing the amine hydrochlorides. 

Another method for slowing oxidation of rubber adhesives is to add a compound which destroys the hydroperoxides formed in step 3, before they can decompose into radicals and start the degradation of new polymer chains. These materials are called hydroperoxide decomposers, preventive antioxidants or secondary antioxidants. Phosphites (phosphite esters, organophosphite chelators, dibasic lead phosphite) and sulphides (i.e. thiopropionate esters, metal dithiolates) are typical secondary antioxidants. Phosphite esters decompose hydroperoxides to yield phosphates and alcohols. Sulphur compounds, however, decompose hydroperoxides catalytically. 

Tawa, R., and Sakurai, H. (1997). Determination of four active oxygen species such as H2O2, OH, OJ and 02 by luminol-and CLA-chemiluminescence methods and evaluation of antioxidative effects of hydroxybenzoic acid. Anal. Lett. 30 2811-2825. 

There are methods to manipulate the backbones of polymers in several areas that include control of microstructures such as crystallinity, precise control of molecular weight, copolymerization of additives (flame retardants), antioxidants, stabilizers, etc.), and direct attachment of pigments. A major development with all this type action has been to provide significant reduction in the variability of plastic performances, more processes can run at room temperature and atmospheric pressure, and 80% energy cost reductions. 

BORS w, HELLER w, MICHEL c and SARAN M (1990) Flavouoids as antioxidants determination of radical-scavenging efficiency Methods in Enzymology 186, 343-55. 

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