Antioxidants concentration range

Absorption of this material by tissues can cause symptoms of iUness that resemble those induced by its o- or m-isomers. For instance, the ingestion of 1 g by an adult or a smaller quantity by a child may induce tinnitis, nausea, dizziness, a sensation of suffocation, an increased rate of respiration, vomiting, pallor, muscular twitching, headache, dyspnea, cyanosis, delirium, and collapse. The literature contains reports of fatal cases that have been caused by the ingestion of 5-12 g. Cases of dermatitis have resulted from skin contact, and have also followed the application of an antiseptic oH that apparently contained traces of hydroquinone added as an antioxidant. The report also describes cases of keratitis and discoloration of the conjunctiva among personnel exposed to this material in concentrations ranging from 10 to 30 mg of... 

Table 4 summarizes the antioxidants, their frequency of use, concentration range, and examples of products containing them. Sulfite, bisulfite, and metabisulfite constitute the majority of antioxidants used in parenteral products despite several reports of... 

Rat hepatocytes were treated with Fe-NTA (nitriloacetic acid) [49]. In this model, all the tested compounds, including tyrosol, were able to inhibit lipoperoxidation in the same concentration range 20-100 pM (hydroxytyrosol, caffeic acid and oleuropein). The antioxidant activity of caffeic acid has been already described in erythrocytes, rat isolated... 

Alpha-tocopherol is a highly lipophilic compound, and is an excellent solvent for many poorly soluble drugs.Of widespread regulatory acceptability, tocopherols are of value in oil- or fat-based pharmaceutical products and are normally used in the concentration range 0.001-0.05% v/v. There is frequently an optimum concentration thus the autoxidation of linoleic acid and methyl linolenate is reduced at low concentrations of alpha tocopherol, and is accelerated by higher concentrations. Antioxidant effectiveness can be increased by the addition of oil-soluble synergists such as lecithin and ascorbyl palmitate. " ... 

Hindered phenols do not show the above-mentioned disadvantages. They are the stabilizers of choice whenever good oxidation stabihty has to be coupled with good color stabihty and, possibly, food approval of the end article. The most important hindered phenols in use are the following NyN -hexamethylenebis-3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionamide, l,l,3-tris-(5-tert-butyl-4-hydroxy-2-methylphenyl-butane, l,3,5-tris-(3,5-di-tert-butyl-4-hydroxybenzyl)-mesitylene, and BHT. The antioxidants can be added already during polycondensation, the normal concentration ranging from 0.3 to 0.7%. 

For stabilization of polyolefins in contact with copper, it is often mandatory to combine a metal deactivator with an antioxidant. Metal deactivators in actual use are essentially N,N -bis-[3-(3, 5 -di-te t-butyl-4 -hydroxy-phenyl)propionyl]-hydrazine and NJV -dibenzaloxalyldihydrazide. The latter compound requires predispersion in a masterbatch because of its insolubility in polyolefins. This is not needed, however, for the former compound, which at commonly used concentrations is molecularly dispersed in polyolefins after processing. The required additive concentrations range from 0.05 to 0.5% depending on the polymer, the nature of the insulation (solid, cellular), whether the cable is petrolatum filled, and on service conditions. 

Following the same procedure, these authors incorporated a-TOC, BHT and fert-bufylhydroquinone (TBHQ) into PLA films at concentrations ranging from 0 to 10%. DSC results showed that the polymer glass transition temperature and the crystallinity slightly decreased with the increase of the antioxidant content. Permeability towards water vapour showed a decrease in the wettability of the prepared materials with the increase of the antioxidants content. Similar results were obtained for gas permeation. Barrier improvements could not be measured at high concentrations due to phase separation. 

In vitro, low concentrations of 17P-oestradiol (10 nM) reduced oxidative modification of normal health men volunteers (with total cholesterol < 5.5 mM) blood LDL in the presence of either ascorbic acid or tocopherol (Huang etal. 1999). Introduction of small amounts of esterified 17 -estradiol into lipoproteins by means of incubation of free 17P-cestradiol 17-stearate in plasma did not result in any antioxidant effect (Meng et al. 1999). Using an artificial transfer system (Celite dispersion), larger amounts of 17P-oestradiol esters could be incorporated into lipoproteins. Concentrations ranging between 0.27 and 1.38 molecules/LDL particle for 17P-oestradiol 17-stearate and between 0.36 and 1.93 molecules/LDL particle for 17P-oestradiol 17-oleate resulted in increased Cu -induced oxidation resistance of LDL, as indicated by statistically significant lag time prolongations. 

Elastomers. Polyunsaturated elastomers are sensitive to oxidation. Stabilizers are added to the elastomers prior to vulcanization to protect the rubber during drying and storage. Nonstaining antioxidants such as buty-lated hydroxytoluene (1), 2,4-bis(octylthiomethyl)-6-methylphenol [110553-27-0], 4,4 -bis(a, a -dimethylbenzyl)diphenylamine (14), or aphosphite such as tris(nonyl-phenyl)phosphite (24) may be used in concentrations ranging from 0.01 to 0.5%. 

Uric acid represents the major catabolite of purine breakdown in humans. Therefore, it remains an important marker molecule for disorders associated with alterations of the plasma urea concentration such as hyperuricemia (gout), renal impairment, leukemia, ketoacidosis, Lesch-Nyhan syndrome and lactate excess. Uric acid may also act as an antioxidant in human body. Consequently its measurement for diagnosis and treatment of some disorders is routinely required. Zhang et developed a reagentless amperometric uric acid biosensor based on carboxyl modified, conductive zinc sulfide (ZnS) Qdots. The biosensor could detect uric acid without the presence of an electron mediator. The fabricated uricase/ZnS Qdot/l-cys biosensor exhibited higher amperometric response compared to the one without Qdots (uricase/l-cys biosensor). They were able to demonstrate a linear dependence on the uric acid concentration ranging from 5.0 x 10 to 2.0 x 10 mol with a detection limit of 2.0 x 10 mol at 3cr. 

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