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PubMedDate not supplied

Ascorbyl stearate inhibits cell proliferation and tumor growth in human ovarian carcinoma cells by targeting the PI3K/AKT pathway.

Ascorbyl stearate is a lipophilic, vitamin C derivative with antitumorigenic properties. The molecular mechanism(s) underlying the anticarcinogenic effect of this compound have not been well documented. The effect of ascorbyl stearate was studied in a panel of human ovarian epithelial cancer cells. Treatment with ascorbyl stearate caused a dose-dependent inhibition of the cell proliferation. The antiproliferative effect was due to the arrest of cells in the S/G2-M-phase of the cell cycle. Treatment of OVCAR-3 cells with ascorbyl stearate also inhibited PI3K/AKT activity. The presence of a constitutively active AKT protected OVCAR-3 cells from the effects of ascorbyl stearate, suggesting that this nutraceutical targets the PI3K/AKT pathway. The administration of ascorbyl stearate by gavage induced involution of human ovarian carcinoma xenografts in nude mice. These studies indicate that the antiproliferative effect of ascorbyl stearate on ovarian epithelial cancer cells is associated with decreased PI3K/AKT activity, and point toward the PI3K/AKT signaling pathway as a target for this drug.

Ascorbic Acid↗
PubMed1998

L-FABP and I-FABP expression increase NBD-stearate uptake and cytoplasmic diffusion in L cells.

The effects of intestinal and liver fatty acid binding protein (I- and L-FABP, respectively) expression on single-cell fatty acid uptake, internalization, and cytoplasmic diffusion were determined in transfected L cell fibroblasts. These parameters were measured using the nonesterifiable fluorescent fatty acid probe 12-N-methyl-(7-nitrobenz-2-oxa-1,3-diazol)aminostearate (NBD-stearate) and fluorescence digital imaging. In single-cell fluorescence imaging experiments, L-FABP-expressing cells, but not I-FABP-expressing cells, increased NBD-stearate uptake 1.7-fold compared with control cells. Both I- and L-FABP increased the cytoplasmic diffusion rate of the internalized NBD-stearate 2.6- and 1.9-fold, respectively, compared with control cells. However, increased NBD-stearate lateral membrane mobility was observed only in L-FABP-expressing cells. After incubation of the cells with 4 microM NBD-stearate at 37 degrees C for 30 min, fluorescence deconvolution imaging indicated that NBD-stearate was localized primarily into lipid droplets in all cell lines. The differential effect of these proteins on fatty acid uptake and intracellular trafficking in single cells illustrates a possible difference in the physiological function of I- and L-FABP in intact cells.

4-Chloro-7-nitrobenzofurazan↗
PubMed1967

The incorporation of acetate, stearate and D(-)-beta-hydroxybutyrate into milk fat by the isolated perfused mammary gland of the goat.

1. Mammary glands of lactating goats were perfused for 12.5-15hr. with heparinized whole blood and infused with a substrate mixture of glucose, acetate and amino acids (and sometimes chylomicra) containing either [1-(14)C]acetate, d(-)-beta-hydroxy[1-(14)C]butyrate or [U-(14)C]stearate. 2. There was a substantial net uptake of acetate by the glands and transfer of radioactivity into milk fat. Acetate was extensively utilized for the synthesis of milk fatty acids of chain length up to C(14) and to a smaller extent for the synthesis of palmitate. 3. There was a small and variable net uptake of stearate and beta-hydroxybutyrate and negligible oxidation of these substrates. However, tissue uptake was demonstrated by a substantial fall in specific radioactivity across the glands and an extensive transfer of radioactivity into milk fatty acids. 4. With beta-hydroxybutyrate the labelling of milk fat was very similar to that with acetate, but the distribution of radioactivity suggested a cleavage into C(2) fragments of about 40%. 5. Labelled stearate gave rise to highly labelled stearate and oleate in the milk fat. Small amounts of radioactivity were detected in stearate of plasma triglycerides and oleate of plasma free fatty acids. 6. In experiments where there was a decline in milk-fat secretion late in perfusion, the milk fatty acids showed a marked decline in the proportion of stearate and oleate and a rise in the proportion of myristate and palmitate. This did not occur in experiments where milk-fat secretion was maintained at a higher level. 7. The present results confirm that there is a large pool of long-chain fatty acids in mammary tissue that can act as an endogenous source of these substrates.

Acetates↗
PubMedDate not supplied

The influence of magnesium stearate on the characteristics of mucoadhesive microspheres.

Microspheres containing the mucoadhesive polymer chitosan hydrochloride, with matrix polymer Eudragit RS, pipemidic acid as a model drug and agglomeration preventing agent magnesium stearate were prepared by the solvent evaporation method. The amount of magnesium stearate was varied and the following methods were used for microsphere evaluation: sieve analysis, drug content and dissolution determination, scanning electron microscopy, x-ray diffractometry, DSC and FTIR spectroscopy. The results showed that average particle size decreased with increasing amount of magnesium stearate used for microsphere preparation. This is probably a consequence of stabilization of the emulsion droplets with magnesium stearate. Higher pipemidic acid content in the microspheres was observed in larger particle size fractions and when higher amounts of magnesium stearate were used. It was also found that these two parameters significantly influenced the dissolution rate. The important reason for the differences in drug content in microspheres of different particle sizes is the diffusion of pipemidic acid from the acetone droplets in liquid paraffin during the preparation procedure. The physical state of pipemidic acid changed from crystalline to mostly amorphous with its incorporation in microspheres, as shown by x-ray diffractometry and differential scanning calorimetry. No differences were observed in the physical state of pipemidic acid and in microsphere shape and surface between different size fractions of microspheres, prepared with different amounts of magnesium stearate. Additionally, no correlation between the physical state of the drug in different microspheres and their biopharmaceutical properties was found.

Acrylic Resins↗
PubMed2005

The influence of magnesium stearate on the Hiestand Tableting Indices and other related mechanical properties of maltodextrins.

Magnesium stearate is widely used as a lubricant in pharmaceutical dosage forms. A film of magnesium stearate, or other lubricant, around individual granules is generally considered to cause the softening of tablets. Maltodextrins were chosen as model excipients since maltodextrins possessing a series of molecular weights showed systematically changing consolidation mechanisms. As maltodextrin molecular weight increases, the plasticity of the material increases. The Hiestand Tableting Indices and other related mechanical properties were used to study the effect of magnesium stearate addition on the mechanical properties and consolidation mechanisms of single component maltodextrins. Magnesium stearate was shown to lower the tensile strengths of maltodextrin compacts. Additionally, magnesium stearate addition lowered both the Hiestand Bonding Index and the Hiestand Brittle Fracture Index. The lower values of the Hiestand Brittle Fracture Index indicate that magnesium stearate promotes greater plastic behavior in maltodextrin compacts.

Drug Stability↗
PubMed2002

Effect of magnesium stearate on the content uniformity of active ingredient in pharmaceutical powder mixtures.

The objective of this study was to determine the effect of magnesium stearate on the physical stability of polydisperse powder mixtures. The effects of concentration of magnesium stearate and the time of lubrication of mixtures with magnesium stearate on the content uniformity of the active ingredient in the mixtures were evaluated in a model mixture of lactose and aspirin. These effects were compared in a random mixture of non-interacting components and a mixture based on particle interaction. A statistical model that adequately described the relationship between the factors examined and the response was generated. The model indicated the presence of an interaction between magnesium stearate concentration and lubrication time. At a given concentration of magnesium stearate, there was a significant reduction in the content uniformity of aspirin as the time of lubrication of the mixture with magnesium stearate was increased. This effect was larger in mixtures based on particle interaction than in random mixtures of non-interacting components.

Aspirin↗
PubMedDate not supplied

Effect of magnesium stearate on chitosan microspheres prepared by an emulsification-coacervation technique.

Chitosan microspheres were prepared using an emulsification-coacervation technique. The w/o emulsion comprised a mixture of light and heavy liquid paraffins containing sodium dioctyl sulphosuccinate as the oil phase and chitosan solution as the aqueous phase. Pentasodium tripolyphosphate was included as a counterion. The chitosan microspheres obtained showed a high degree of aggregation. This was markedly reduced, by the incorporation of magnesium stearate in the disperse phase. The resultant microspheres were then discrete, spherical with smooth surfaces. Additionally, with an increasing magnesium stearate content, larger-sized microspheres were produced. The DSC analysis data suggested that the magnesium stearate was converted to stearic acid during the preparation process. Chitosan microspheres containing propranolol hydrochloride were similarly prepared, but their surface was convoluted and their shape not well defined. Unlike the microspheres without drug, the size of the drug-loaded microspheres decreased with increasing magnesium stearate content. The release of propranolol hydrochloride from the microspheres was fast, irrespective of the content of magnesium stearate. Drug encapsulation efficiency was enhanced when a greater amount of magnesium stearate was used.

Animals↗
PubMed2000

A comparative efficacy and safety study of clarithromycin, roxithromycin and erythromycin stearate in mild pneumonia.

The efficacy and safety of clarithromycin, roxithromycin and erythromycin stearate in mild pneumonia were compared in an open randomized trial. Eighty-six male patients, doing their obligatory military service, ranging between 19 and 24 years of age (mean 20), were randomly treated: 29 with clarithromycin 500 mg 12-hourly, 30 with roxithromycin 150 mg 12-hourly, and 27 with erythromycin stearate 500 mg 6-hourly, each course being administered for 10 days. Seventy-eight patients were able to be evaluated for efficacy, 28 receiving clarithromycin, 28 roxithromycin, and 22 erythromycin stearate. There were no significant differences among the groups in terms of clinical success rates (clinical cure or improvement: 89% for clarithromycin, 82% for roxithromycin, and 73% for erythromycin stearate, p = 0.32). However, we found that there were significant differences among the groups in terms of clinical cure rates (75% for clarithromycin, 64% for roxithromycin, and 41% for erythromycin stearate, p = 0.04). Adverse events, mostly gastrointestinal, caused discontinuation of treatment in 3.4% of the patients in the clarithromycin group, in 6.6% of the patients in the roxithromycin group, and in 18.5% of the patients in the erythromycin stearate group. The results indicate that there were no statistically significant differences among the three treatment groups in terms of clinical success rates, but that clarithromycin and roxithromycin were better tolerated.

Adult↗
PubMed1987

Lead level of whole blood and plasma in workers exposed to lead stearate.

In a group of 23 male workers exposed to lead stearate the levels of lead in whole blood and plasma were determined and compared to those obtained from a group of 23 subjects exposed to inorganic lead compounds. The mean values for lead in whole blood were similar in both groups, while the mean lead concentration in plasma was 0.1729 (SD 0.0677) mumol/l for those exposed to lead stearate and 0.0936 (SD 0.0577) mumol/l for those exposed to other lead compounds. The difference was highly significant. The percentage ratio for lead in plasma to lead in whole blood, which can be considered a "bioavailability index" for lead, proved to be two times higher for stearate workers than for subjects exposed to inorganic lead compounds. The data suggest that the different chemical properties of absorbed lead stearate may cause a different distribution of the metal in different blood compartments, the plasma compartment having a higher affinity for lead stearate than for other lead compounds. Because the plasma fraction has a greater bioavailability, lead stearate could induce toxic effects that differ (possibly being severer) from those caused by other lead compounds at similar absorbed doses.

Air Pollutants, Occupational↗
PubMed2003

[The dry binders, Vivapur 102, Vivapur 12 and the effect of magnesium stearate on the strength of tablets containing these substances].

Vivapur is microcrystalline cellulose manufactured by the German firm J. Rettenmeier & Söhne GmbH + Co. The types Vivapur 102 and 12 enjoy priority use as dry binders for direct tablet compression. The present paper evaluates tensile strength of tablets made from these substances and the effect of an addition of the lubricant magnesium stearate in connection with its concentration and the conditions of the process of mixing, particularly the period and intensity of mixing. The tested concentrations of stearate were 0.4 and 0.8%, the tested periods of mixing being 2.5, 5, 10, and 20 minutes, intensities of mixing 17 and 34 rot./min. Sensitivity of dry binders to added stearate was evaluated by means of the LSR (lubricant sensitivity ratio) values. The results demonstrated higher sensitivity to an addition of the lubricant in Vivapur 12 than in Vivapur 102. In the first part of the paper focused on the effect of stearate concentration on tensile strength of tablets, Vivapur 102 was also compared with Avicel PH-102. Tablets from Vivapur 102 alone were stronger than those from Avicel PH-102. A concentration of stearate of 0.8% decreased the binding capacity of Vivapur 102 more than that of Avicel PH-102. With a prolonged period of mixing and increased intensity of mixing with stearate, tensile strength of tablets from both Vivapur types was decresed, and a prolonged period of mixing exerted a more marked effect on Vivapur 12 and increased intensity of mixing, on Vivapur 102.

Cellulose↗
PubMedDate not supplied

Determination of magnesium stearate in capsule- or tablet-type supplements.

A simple method for the determination of magnesium stearate in capsule- or tablet-type supplements was developed. Free stearic acid in the sample was removed by extraction with tetrahydrofuran. The remaining stearate was converted to stearic acid by reaction with a cation-exchange resin. The resulting stearic acid was determined by gas chromatography with a polar column. Esters of stearic acid were not converted to stearic acid and would not cause a positive error in the amount of stearate. The amount of magnesium stearate was calculated based on the stearic acid concentration thus obtained. Magnesium stearate levels in 5 out of 25 supplements exceeded 2500 microg/g, which indicated the possible admixture of magnesium stearate.

Calibration↗
PubMed1976

[Studies on erythromycin stearate capsules (OE-7) (author's transl)].

The blood concentration and urinary excretion of OE-7 (erythromycin stearate capsules) and control drug were investigated in 6 volunteers having gastroptosis. OE-7, newly arranged capsules containing erythromycin stearate, was investigated and obtained the results of high blood concentration by oral administration. To confirm the above, we measured blood concentration and urinary excretion of OE-7 comparing with ordinary erythromycin stearate capsules in 6 volunteers having gastroptosis. The peaks of blood concentration were noted at 3 hours after administration in 6 volunteers uniformly. The mean maximum blood concentration of OE-7 was 1.17 mcg/ml which was significantly higher than ordinary erythromycin stearate capsules. In time course of mean blood concentration, the blood concentration levels of OE-7 were higher than those of control erythromycin stearate capsules at any measurement. Effective blood levels were continuously high in OE-7. Urinary excretion of OE-7 reached to the maximum from 4 to 6 hours after administration which was also higher than control erythromycin stearate. Clinical efficacy of OE-7 was investigated in 28 cases in acute respiratory infection. The results noted were excellent in 5 cases (17.9%), good in 16 cases (57.1%), no change in 6 cases (21.4%), and undetermined in 1 case (3.6%). There were 5 cases of slight gastro-intestinal discomfort as the side effects. As the conclusion, OE-7 revealed good bioavailability and seemed to be useful antibiotic for acute respiratory infections.

Adult↗
PubMed2001

Final report on the safety assessment of Octyidodecyl Stearoyl Stearate.

Octyldodecyl Stearoyl Stearate functions as an occlusive skin-conditioning agent and as a nonaqueous viscosity-increasing agent in many cosmetic formulations. Current concentrations of use are between 0.7% and 23%, although historically higher concentrations were used. The chemical is formed by a high-temperature, acid-catalyzed esterification reaction of long-chain alcohols (primarily C-20) and a mixture of primarily C-18 fatty acids. Levels of stearic acid, octyldodecanol, and octylydocecyl hydroxystearate in the final product are 5% or less--no other residual compounds are reported. Only limited safety test data were available on Octyldodecyl Stearoyl Stearate, but previous safety assessments of long-chain alcohols and fatty acids found these precursors to be safe for use in cosmetic formulations. Octyldodecyl Stearoyl Stearate produced no adverse effects in acute exposures in rats. The chemical was mostly nonirritating to animal skin at concentrations ranging from 7.5% to 10%; one study did find moderate irritation in rabbit skin at a concentration of 7.5%. Clinical tests at a concentration of 10.4% confirmed the absence of significant irritation in humans. An ocular toxicity study in rabbits found no toxicity. No evidence of genotoxicity was found in either a mammalian test system or in the Ames test system, with or without metabolic activation. The available data on Octyldodecyl Stearoyl Stearate and the previously considered data on long-chain alcohols and fatty acids, however, did not provide a sufficient basis to make a determination of safety. Additional data needs include (1) chemical properties, including the octanol/water partition coefficient; and (2) if there is significant dermal absorption or if significant quantities of the ingredient may contact mucous membranes or be ingested, then reproductive and developmental toxicity data may be needed. Until such time as these data are received, the available data do not support the safety of Octyldodecyl Stearoyl Stearate as used in cosmetic formulations.

Animals↗
PubMed2004

[Structural characterization of rare-earth stearate and its thermal stability mechanism for PVC].

Structural characterization of rare-earth stearate was conducted by FTIR and XRD. The results show that the bonds between the stearate and rare-earth metal ions in rare-earth stearate are main ionic character and have the stratified crystalline structure with the crystal layer formed from a plane layer of rare-earth ions combined with two layers of fully extended zigzag chains of stearic acid radicals arranged parallell to each other on its both sides, and the rare-earth ions axes are inclined to the crystal layer planes in it. Congo red test showed that the stabilizing time increased when the stabilizers' concentration increased. The order of stability of this four rare-earth stearates is Last>Ndst>Yst>Dyst. Furthermore, the thermal stability mechanism of rare earth stearate for PVC has been presumed by FTIR. The results indicate that Last and Ndst can bate the chain reaction and exchange the labile functional groups in the backbone chains for other more stable substituents derived from the stabilizer and change the framework, while Yst and Dyst's effect is not clear.

Metals, Rare Earth↗
PubMed1989

Determination by gas-liquid chromatography of trace amounts of soft polyvinyl chloride plastic additives in aqueous solutions. II. Di(2-ethylhexyl) phthalate, epoxidized vegetable oils and stearates.

A method for the determination of di(2-ethylhexyl) phthalate (DEHP), epoxidized vegetable oils (EVO) and stearates in aqueous solutions is described. A stepwise extraction procedure is employed to separate DEHP and EVO from the stearates, using n-hexane as extraction solvent. EVO is transesterified to methyl esters by sodium methoxide in methanol. The stearates are derivatized by methanol containing sulfuric acid. The alkyl esters are analyzed by gas-liquid chromatography, using 3% OV-210 as the stationary phase. The concentrations of the weakest standard solutions correspond to 10, 5 and 8 micrograms/l (ppb) of DEHP, EVO and stearates, respectively, in the aqueous samples. The method is used for the determination of DEHP, EVO and stearates in intravenous solutions stored in flexible polyvinyl chloride bags.

Chromatography, Gas↗
PubMed2001

An examination of the moisture sorption characteristics of commercial magnesium stearate.

The objective of this study was to characterize the moisture sorption of magnesium stearate and the morphological changes, if any, resulting from moisture sorption. Six samples of commercial magnesium stearate USP were examined. Moisture sorption isotherms were obtained at 25 degrees C and 5% to 98% relative humidity (RH) using a moisture balance. Changes in crystal form resulting from moisture sorption were determined by x-ray diffraction. There were differences in the shape of the isotherm, reversibility of moisture uptake, and shape of the hysteresis loop in the isotherms of crystalline and amorphous magnesium stearates. The isotherm of crystalline magnesium stearate was almost parallel to the pressure axis until an RH of ~80% was reached, when there was desorption of practically all of the adsorbed water. The isotherm of the amorphous sample was characterized by continuous uptake of water over the entire range of RH. Exposure of amorphous magnesium stearate to RH greater than 70% resulted in the formation of the trihydrate. The trihydrate was converted into the anhydrous form when heated to a temperature of 100 degrees C to 105 degrees C. The trihydrate could be generated by exposing the anhydrate to RH higher than 70%.

Adsorption↗
PubMed1976

Binding of nitroxide stearate spin labels to bovine serum albumin.

1. 12-Nitroxide stearate binds to bovine serum albumin at about four independent and equivalent binding sites with an association constant of about 10(6) M-1. The binding at these high affinity binding sites is significantly reduced by addition of unlabeled stearate. These data suggest that nitroxide stearates probe the high affinity binding sites for long-chain fatty acids. 2. Qualitative analyses of the ESR spectra of 5-, 12- and 16-nitroxide stearate bound to bovine serum albumin and measurements of the interaction of these compounds so bound with ferricyanide ion provide a rough description of the binding site as follows: the polar headgroup of the spin-labeled fatty acid is rigidly fixed, but fairly accessible to paramagnetic ions. The middle part of the hydrocarbon chain of bound stearate spin label also is rigidly fixed but differs in being shielded from the solvent, presumably by a hydrophobic cleft. The methyl terminus shows greater motion, appearing to move within a narrow cone, and also appears to be somewhat accessible to paramagnetic ions.

Binding Sites↗
PubMed1967

The oxidation and utilization of palmitate, stearate, oleate and acetate by the mammary gland of the fed goat in relation to their overall metabolism, and the role of plasma phospholipids and neutral lipids in milk-fat synthesis.

1. Measurements were made of milk yield, mammary blood flow and arteriovenous differences of each plasma lipid fraction, and their specific radioactivities, during the infusion of [U-(14)C]stearate, [U-(14)C]oleate, [U-(14)C]palmitate and [1-(14)C]acetate into fed lactating goats. 2. Entry rates of fatty acids into the circulation were 4.2mg./min./kg. body wt. for acetate, and 0.18, 0.28 and 0.42mg./min./kg. for stearate, oleate and palmitate respectively. Acetate accounted for 23% of the total carbon dioxide produced by the whole animal, and contributed to the oxidative metabolism of the mammary gland to about the same extent. Corresponding values for each of the long-chain acids were less than 1%. 3. There were no significant arteriovenous differences of phospholipids, sterols or sterol esters, and their fatty acid composition showed no net changes during passage through the mammary gland. 4. There were large arteriovenous differences of plasma triglycerides, and their fatty acid composition showed marked changes across the gland. The proportions of palmitate and stearate fell, and that of oleate increased. 5. Arteriovenous differences of plasma free fatty acids (FFA) were small and variable, but a large fall in the specific radioactivity of each of the long-chain acids examined indicated substantial uptake of plasma FFA, accompanied by roughly equivalent FFA release from mammary tissue. The uptake of FFA was confirmed by the extensive transfer of radioactivity into milk. The FFA of milk were similar in composition and radioactivity to the milk triglyceride fatty acids, and quite unlike plasma FFA. 6. The formation of large amounts of oleic acid (18-21 mg./min.) from stearic acid was demonstrated. 7. During the terminal stages of the [(14)C]acetate infusion, milk triglyceride fatty acids of chain length C(4)-C(14) showed specific radioactivities that were 75-90% of that of blood acetate, and that of palmitate was roughly one-quarter of this value. Oleate and stearate were unlabelled. 8. The results confirmed that milk fatty acids of chain length C(4)-C(14) arise largely from blood acetate, and palmitate is derived partly from acetate and partly from plasma triglyceride, the latter fraction being almost the sole precursor of oleate and stearate.

Journal Article↗