Ascorbic stearate

Sodium, potassium, and calcium salts of ascorbic acids are called ascorbates and are used as food preservatives. These salts are also used as vitamin supplements. Ascorbic acid is water-soluble and sensitive to light, heat, and air. It passes out of the body readily. To make ascorbic acid fat-soluble, it can be esterified. Esters of ascorbic acid and acids, such as palmitic acid to form ascorbyl palmitate and stearic acid to form ascorbic stearate, are used as antioxidants in food, pharmaceuticals, and cosmetics. 

A second surface modification has been reported by Yamamoto et al. These workers added stearic acid to their carbon paste mixture. This produced an electrode which was relatively insensitive to ascorbic acid and DOPAC relative to dopamine. It is theorized that this electrode works because of electrostatic repulsion of the anionic ascorbate and DOPAC by surface stearate groups. Ionic repulsion has also been employed by covering the surface of the working electrode with an anionic polymer membrane. Gerhardt et al. used Nafion, a hydrophobic sulfonated perfluoro-polymer, to make a dopamine selective electrode. This electrode exhibited selectivity coefficients as large as 250 1 for dopamine and norepinephrine over ascorbic acid, uric acid, and DOPAC. 

E 304 Fatty acid esters of ascorbic acid (i) Ascorbyl palmitate (ii) Ascorbyl stearate... 

E 304 esters of fatty acids with ascorbic acid (i) ascorbyl palmitate (ii) ascorbyl stearate quantum satis... 

For non-standardised products tocopherols, tocopherol acetate, ascorbic acid and its sodium and calcium salts, ascorbyl palmitate, ascorbyl stearate, eiythorbic acid and stannous chloride (max. 0.0015% calculated as tin) may be used according to good manufacturing practice. 

Aqua, glycerin, cyclomethicone, dicaprylyl carbonate, ascorbic acid, butyrospermum parkii, alcohol cetearyl, octocrylene, glyceryl stearate, C12-15 alkyl-benzoate, cera microcristallina, tocopheryl acetate, vitis vinifera, PEG-40 stearate, sodium carbomer, paraffinum liquid-urn, tetrasodium iminodisucciunate, BHT, phenoxyethanol, methyl paraben, propyl paraben, diazolidinyl urea and parfum. 

Ascorbyl palmitate and ascorbyl stearate are synthetic derivatives of ascorbic acid. Ascorbic palmitate is soluble in lipid-containing foods because of its relatively good hydrophobicity (88). Ascorbyl palmitate is hydrolyzed by the digestive system to provide nutritionally available ascorbic acid and palmitic acid, but health claims cannot be made for its vitamin C contribution. 

Lyne and O Neil [117] reported the in vivo detection of dopamine using stearate-modified carbon-Nujol paste electrodes. Prior to their work, the detection of dopamine by voltammetric techniques was hindered primarily due to the coexisting ascorbic acid in the extracellular fluid of the mammalian brain. Ascorbic acid oxidizes at electric potentials similar to that of dopamine on many electrode materials. These authors found that the use of stearate-modified carbon-Nujol paste electrodes retards the electro-oxidation of anionic species (such as ascorbate) to such an extent that the cationic dopamine species could be detected in their presence. 

Ascorbic acid was used to prevent the oxidation of olive oil, milk, arachis nut oil, lard, ethyl ester of lard, cottonseed oil, pork, and beef fat (4) data showing activity alone and as a synergist are reviewed. Ascorbyl laurate, myristate, palmitate, and stearate were similarly active, although only AP is listed as a preservative in GFR. Ascorbic acid synergy with tocopherol was also reviewed. 

In another formulation, the each gram of 4% cream contains 40 mg hydroquinone USP, 80 mg padimate O USP, 30 mg dioxybenzone USP, and 20 mg oxybenzone USP in a vanishing-cream base of purified water USP, glycerol monostearate and polyoxyethylene stearate, oot-yldodecyl stearoyl stearate, glyceryl dilaurate, quater-nium-26, cetearyl alcohol and ceteareth-20, stearyl alcohol NF, propylene glycol USP, diethylaminoethyl stearate, polydimethylsiloxane, polysorbate 80 NF, lactic acid USP, ascorbic acid USP, hydroxyethyl cellulose, quatemium-14 and myristalkonium chloride, edetate disodium USP, and sodium metabisulfite NF. 

Ascorbic acid (Sigma), magnesium stearate (CIA-Estearina Parananheci), magnesium trisilicate (Farmar), and Si02 (Cab-O-Sd) were used without further purification. 

Ascorbic acid samples as well as binary mixtures of ascorbic acid and the considered excipients were investigated. The binary mixtures were prepared taking into account the shoichiometry generally used for the preparation of ascorbic acid tablets ascorbic acid (500 mg, of a 100 mesh sample), magnesium stearate (6.7 mg), magnesium trisilicate (13.3 mg), and Si02 (1.0mg). The compounds were mixed in a mortar. 

Figure 3.17 TG curves for (a) ascorbic acid, (b) magnesium stearate, and (c) ascorbic acid/ magnesium stearate binary mixture.

Based on the TG and DSC experimental results it can be concluded that the excipients, that is, magnesium stearate, magnesium trisilicate, and Si02, have no substantial influences on the thermal stabihty of ascorbic acid. This result shows that the three compounds can be used (at least from a thermal point of view) as excipients, with no restrictions, for ascorbic acid tablet formulations, since they will not provoke or accelerate the thermal degradation of ascorbic acid. However, by comparison of Tables 3.5 and 3.7, it is evident that the temperature of the... 

Anoxomer L-Ascorbic acid Ascorbyl palmitate Ascorbyl stearate BHA BHT t-Butyl hydroquinone 3-t-Butyl-4-hydroxyanisole Calcium citrate Calcium disodium EDTA... 

L-Ascorbic acid Cupric sulfate anhydrous Potassium nitrate Sodium nitrate fixative, color poultry curing Potassium nitrite fixative, color red meat curing Potassium nitrite fixative, cosmetic creams/lotions Isocetyl stearate fixative, cosmetics Caprylic/capric/lauric triglyceride Caprylic/capric/linoleic triglyceride Isocetyl laurate Isocetyl myristate Methyl hydrogenated rosinate PEG-175... 

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. 

Lubricant substances which are reported in literature as suitable for effervescent manufacturing because they are water soluble are sodium benzoate, sodium acetate, L-leucine, and Carbowax 4000. A very recent application is a combination of calcium and potassium sorbates, micronized polyethylene glycol with calcium ascorbate or trisodium citrate (20). Combination of spray-dried L-leucine and polyethylene glycol 6000 has been reported as a successful lubricant in the literature (21). Other less soluble lubricants have been used in formulating effervescent tablets, however, a balance should be found between compression efficiency and water solubility. Magnesium stearate is also employed but the most suitable, commercially available type is its combination with sodium lauryl sulfate, a surface-active agent that helps in its dispersion (22). 

Substances with antioxidant effects (Table 11.4) that maybe used in food production in the necessary quantities include fatty acids esters of ascorbic acid (palmitate, stearate, see Section 5.14.4), natural products containing tocopherols and synthetic a-, (5-, y-and 5-tocopherol, which are identical to natural tocopherols, and rosemary extracts. 

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