Sodium ascorbyl phosphate in topical microemulsions

Sodium ascorbyl phosphate is a hydrophilic derivative of ascorbic acid, which has improved stability arising from its chemical structure. It is used in cosmetic and pharmaceutical preparations since it has many favorable effects in the skin, the most important being antioxidant action. In order to achieve this, it has to be converted into free ascorbic acid by enzymatic degradation in the skin. In the present work, o/w and w/o microemulsions composed of the same ingredients, were selected as carrier systems for topical delivery of sodium ascorbyl phosphate. We showed that sodium ascorbyl phosphate was stable in both types of microemulsion with no significant influence of its location in the carrier system. To obtain liquid microemulsions appropriate for topical application, their viscosity was increased by adding thickening agents. On the basis of rheological characterization, 4.00% (m/m) colloidal silica was chosen as a suitable thickening agent for w/o microemulsions and 0.50% (m/m) xanthan gum for the o/w type. The presence of thickening agent and the location of sodium ascorbyl phosphate in the microemulsion influenced the in vitro drug release profiles. When incorporated in the internal aqueous phase, sustained release profiles were observed. This study confirmed microemulsions as suitable carrier systems for topical application of sodium ascorbyl phosphate.     

Skin protection against ultraviolet induced free radicals with ascorbyl palmitate in microemulsions.

UV irradiation induces free radical formation in the skin. UV filters and antioxidants can be used for protection. In the present work, the amphiphilic antioxidant ascorbyl palmitate has been investigated and its effectiveness against free radical formation in porcine skin determined with electron paramagnetic resonance (EPR) spectroscopy with a spin trapping technique. 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline-N-oxide (DEPMPO) was used as spin trap. In this study, three different radicals were identified in UV irradiated porcine ear skin: two originated from sulphur centred radicals (SO(3)*), while the third was the carbon-centred acyl (C=O*) radical. Ascorbyl palmitate applied on the skin decreased the level of formation of free radicals. Its effectiveness depended significantly on the carrier system - the type of microemulsion and its concentration, while the time of application had no influence on its effectiveness. Oil in water microemulsions delivered ascorbyl palmitate to the skin significantly better than water in oil microemulsions. In both types of microemulsions, the effectiveness increases at higher concentrations of ascorbyl palmitate.     

Effect of colloidal carriers on ascorbyl palmitate stability.

Active compounds can be protected against degradation by incorporation into colloidal carrier systems. The stabilizing effect of carrier systems for ascorbyl palmitate (AP) was investigated using microemulsions (ME), liposomes and solid lipid nanoparticles (SLN). Analysis of chemical stability by HPLC showed that AP is most resistant against oxidation in non-hydrogenated soybean lecithin liposomes, followed by SLN, w/o and o/w ME, and hydrogenated soybean lecithin liposomes. The molecular environment of the AP-like nitroxide probe (C(16)-Tempo) in colloidal carriers was characterized using electron paramagnetic resonance (EPR) spectroscopy. We have found that the nitroxide groups are located in environments with different polarity and mobility. The hydrophilic part of AP is the reactive moiety, and high stability is obtained in systems in which this part is exposed to a less polar environment. Additionally, the determined accessibility of nitroxide groups to reduction correlated well with the chemical stability of AP. It is more deeply immersed in the interface when entrapped in a liquid-state carrier than when applied in gel-state particles. Encapsulation of AP in SLN core leads to greater stability. We conclude that the location of the sensitive group of the drug-molecule in a carrier system is crucial for its stability.     

药用辅料抗坏血酸棕榈酸酯的细菌内毒素检查法研究

目的:建立"三氯甲烷溶解后加水振荡萃取"抗坏血酸棕榈酸酯细菌内毒素检查方法.方法:抗坏血酸棕榈酸酯,加入三氯甲烷使溶解,加入不同体积的BET水,旋涡混匀30 s以上,5000 r·min-1离心2 min,取上清液,制成供试品溶液和供试品阳性对照,抗坏血酸棕榈酸酯浓度在相当于1.0 mg·mL-1以下时,对λ为0.25...     

Evaluation of the surfactant properties of ascorbyl palmitate sodium salt.

In this paper we report on the physicochemical surface properties of ascorbyl palmitate (Asc16) and of its sodium salt (Asc16Na) with a view to their use as surfactants. Asc16Na was synthesized from ascorbyl palmitate by neutralizing the -OH groups in position 3 of the ascorbyl ring. The acid-base properties, thermal analysis and stability of Asc16Na monomers were determined. Self-assembling parameters of micellar aggregates in aqueous dispersions through critical micellar concentration (CMC) and critical micellar temperature (CMT) were measured. Asc16Na micellar dispersions efficiently solubilize poorly soluble drugs such as phenacetin and griseofulvin, and enhance their apparent solubility in aqueous environments. Stability tests showed that Asc16Na is more unstable than ascorbyl palmitate. Ascorbyl palmitate and its sodium salt are insoluble at room temperature in water, but their solubilities strongly depend on temperature, and largely increase above the CMT. Although Asc16Na is insoluble at room temperature, it is more soluble than Asc16, and its CMT significantly lowers in the undissociated acidic form. The apparent solubilities of phenacetin and griseofulvin are increased in Asc16Na aqueous solutions. The Asc16Na potential use as surfactant is restricted by its low stability in water, therefore the addition of some antioxidant species is necessary.     

Development of ascorbyl palmitate nanocrystals applying the nanosuspension technology

Ascorbyl palmitate (AP) is an antioxidant used in both cosmetics and food industry. Owing to its poor solubility and instability caused by oxidation having been observed in several colloidal systems, the aim of this study was to investigate the feasibility of applying the nanosuspension technology by high-pressure homogenization (HPH) (DissoCubes) technology) to enhance the chemical stability of AP, followed by lyophilization. Sodium dodecyl sulfate (SDS) and Tween 80 were chosen as emulsifying agents to stabilize the developed AP nanosuspensions. After 3 months of storage at three different temperatures (4 degrees C, 25 degrees C and 40 degrees C), the photon correlation spectroscopy (PCS) analysis of AP nanosuspensions revealed that the mean particle size of those stabilized with SDS significantly increased compared to those stabilized with Tween 80. The results observed from both atomic force microscopy (AFM) and scanning electron microscopy (SEM) revealed AP nanocrystals of cubic-like shape. The percentage of AP remaining in nanosuspensions stabilized with Tween 80 was higher than 90% after 3 months storage at 4 degrees C, 25 degrees C and 40 degrees C. To increase the chemical stability of AP nanosuspensions, a drug powder was prepared by lyophilization. The effect of the presence of cryoprotectant trehalose on the physical stability was evaluated at different concentrations. After redispersing the lyophilized product, the mean size of AP nanosuspensions without trehalose was significantly higher compared with the system with trehalose. After 3 months of storage at 25 degrees C the mean size of lyophilized AP nanosuspensions remained constant. X-ray diffraction revealed the crystalline character of AP nanocrystals after HPH and lyophilization.     

Stability of vitamins C and E in topical microemulsions for combined antioxidant therapy

An interesting strategy for protecting skin from excessive exposure to free radicals is to support the skin endogenous antioxidant system. As the balance between different skin antioxidants is very important, a combined therapy using at least two antioxidants is desirable. In the present work, o/w, w/o, and gel-like microemulsions (ME), all composed of the same ingredients, were selected as carrier systems for dermal delivery of vitamins C and E. Gel-like ME was found to offer the best protection for both vitamins, although other ME also significantly increased their stability compared with that solution. In the presence of vitamin C no decrease in vitamin E content occurred. To obtain ME appropriate for dermal use, their viscosity was increased by adding thickening agents. On the basis of visual examination of viscosity and physical stability of thickened systems, several thickeners were selected. The addition of thickener significantly increased the viscosity of ME and changed the behavior of systems from ideal Newtonian to thixotropic. Finally, the stability of both vitamins was examined as a function of thickening agent and of the location of vitamins in the ME. The addition of thickeners changed the stability of at least one vitamin, but the systems generally still protected vitamins better than solutions. It is likely that the changes in internal organization of ME resulting from the addition of thickener, confirmed by thermal analysis and changes in solubility of oxygen in the outer phase, were the most important factors that influenced the stability of vitamins in thickened systems.     

Biodistribution of ascorbyl palmitate loaded doxorubicin pegylated liposomes in solid tumor bearing mice

The aim of this study is to develop ascorbyl palmitate (ASP) loaded doxorubicin (DOX) pegylated liposomes and to evaluate their targeting potential to tumor. We have prepared conventional (DL), pegylated DOX liposomes with (SDL) and without ascorbyl palmitate (SDL-A). The vesicle size in all the formulations was within the range 105-120 nm and in vitro release studies in serum confirmed the stability of the liposomes. Biodistribution studies carried out in Ehrlich ascites tumor bearing mice indicate higher area under the curve for SDL and SDL-A liposomes compared to DL and plain drug solution. Drug targeting index assessed from tumor-to-serum concentration ratio and therapeutic availability of DOX in tumor tissue was also significantly higher for pegylated liposomes. In conclusion, biodistribution study reveals that the presence of ascorbyl palmitate alters the distribution pattern of liposomes and paves way for better drug targeting.     

Positively charged microemulsions for topical application

The study reports pig-skin permeation and skin accumulation of miconazole nitrate (MCZ) from positively charged microemulsions containing water, 1-decanol/1-dodecanol (2:1, w/w), lecithin and/or decyl polyglucoside at different weight ratios, propylene glycol, 1,2 hexanediol and a cationic charge-inducing agent (stearylamine (ST), l-alanine benzyl ester (ALAB) or cetyltrimethylammonium bromide (CTAB)). Zeta-potential values of the positively charged microemulsions ranged from 14.2 to 37.5 mV and mean droplet size from 6.0 to 16.8 nm. In vitro pig-skin permeation of MCZ after a single 24h application was negligible for all microemulsions; accumulation from positively charged microemulsions was nearly twice that from their negatively charged counterparts. The increased accumulation might be ascribed to the interaction between positive microemulsive systems and negatively charged skin sites; no significant difference was observed among the various cationic charge-inducing agents. Skin accumulation from the microemulsion containing most lecithin was lower than those of other microemulsions; this was ascribed to the phase transformation from microemulsion to a liquid crystal system after skin contact. These results suggest that positively charged microemulsions could be used to optimize drug targeting without a concomitant increase in systemic absorption; ALAB, an ester of a natural amino acid, is an appropriate cationic charge-inducing agent.     

Chitosan derivative nanocarrier: Safety evaluation,antibacterial property and ascorbyl palmitate encapsulation

A chitosan derivative, methyl ether-terminated poly(ethylene oxide)-4-methoxycinnamolyphthaloylchitosan (PCPLC) was prepared, characterized and self-assembled into nanoparticles. Encapsulation of ascorbyl palmitate (AP) into PCPLC gave 689 ± 0.98 nm particles with encapsulation efficiency of 84% at 56% drug loading. The encapsulated AP showed significant improved stability as examined by ¹H NMR spectroscopy. The obtained particles displayed no short-term cytotoxicity against the human skin melanoma A-375 cell line using the MTT assay and no short-term skin irritation on human volunteers using a single topical application as patch and photopatch tests. In addition, aqueous suspension of PCPLC nanoparticles successfully inhibited the growth of Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923.     

Comparison of the effects of ascorbyl palmitate and L-ascorbic acid on paracetamol-induced hepatotoxicity in the mouse

The effects of ascorbyl palmitate (ASCP) and free L-ascorbic acid (LAA) on the hepatotoxicity of paracetamol (acetaminophen) and the in vivo covalent binding of reactive paracetamol metabolites to hepatic proteins has been studied in male MF1 mice. The oral administration of [3H(G)]paracetamol (600 mg/kg) resulted in covalent binding to hepatic proteins, a depletion of hepatic non-protein sulphydryl (NPS) groups after 2 h, and a marked elevation of plasma alanine aminotransferase (ALAT) activity after 24 h. The co-administration of paracetamol and ASCP (1412 mg/kg, equivalent to 600 mg/kg free LAA), but not paracetamol and LAA (600 mg/kg), significantly reduced covalent binding of paracetamol metabolites at 2 and 4 h after treatment. In addition ASCP, but not LAA, significantly reduced the depletion of NPS groups and the elevation of plasma ALAT activity. ASCP also completely prevented the 35% mortality observed at 24 h in paracetamol treated mice. These results demonstrate that ASCP, but not LAA, when co-administered orally with the analgesic is an effective inhibitor of paracetamol-induced hepatotoxicity in the mouse. The mechanism by which ASCP prevents liver injury appears to involve destruction of reactive paracetamol metabolites which is associated with a sparing action on hepatic reduced glutathione levels.     

Skin permeation enhancement of ascorbyl palmitate by liposomal hydrogel (lipogel) formulation and electrical assistance

To enhance skin permeation of ascorbyl palmitate (AsP), it was encapsulated in liposomes, and formulated into liposomal hydrogel (lipogel) by dispersing the liposome into poloxamer hydrogel matrix. To improve the skin permeation of AsP, we applied electric current supplying system that mimics an electric skin massager. We evaluated the effects of composition and surface charge of the liposomes and electrical assistance on the skin permeation of AsP. In the passive transport study, the permeated amounts of AsP from all the lipogels tested were higher than that of control hydrogel which contains Transcutol used to solubilize AsP. In the cathodal delivery condition with a fixed cathodal current of 0.4 mA/cm2, the skin permeation characteristics of the negative lipogels were superior to that obtained with the neutral lipogels and the drug permeation was more increased with increased surface negative charge of the liposomes. In conclusion, the lipogel system was thought as a helpful drug delivery system to enhance skin permeation of AsP. Combined use of negative lipogel with cathodal electric assistance was found to be promising in enhancing the skin delivery of AsP.     

Solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) for application of ascorbyl palmitate

The aim of this study was to improve the chemical stability of ascorbyl palmitate (AP) in a colloidal lipid carrier for its topical use. For this purpose, AP-loaded solid lipid nanoparticles (SLN), nanostructured lipid carriers (NLC) and for comparison, a nanoemulsion (NE) were prepared employing the high pressure homogenization technique and stored at room temperature (RT), 4 degrees C and 40 degrees C. During 3 months, physical stability of these formulations compared to placebo formulations which were prepared by the same production method, was studied including recrystallization behaviour of the lipid with differential scanning calorimetry (DSC), particle size distribution and storage stability with photon correlation spectroscopy (PCS) and laser diffractometry (LD). After evaluating data indicating excellent physical stability, AP-loaded SLN, NLC and NE were incorporated into a hydrogel by the same production method as the next step. Degradation of AP by HPLC and physical stability in the same manner were investigated at the same storage temperatures during 3 months. As a result, AP was found most stable in both the NLC and SLN stored at 4 degrees C (p > 0.05) indicating the importance of storage temperature. Nondegraded AP content in NLC, SLN and NE was found to be 71.1% +/- 1.4, 67.6% +/- 2.9 and 55.2% +/- 0.3 after 3 months, respectively. Highest degradation was observed with NE at all the storage temperatures indicating even importance of the carrier structure.     

Cremophor-free intravenous microemulsions for paclitaxel II. Stability, in vitro release and pharmacokinetics

Two cremophor-free microemulsion systems LBMW (lecithin:butanol:myvacet:water) and CMW (capmul:myvacet:water), for intravenous (IV) administration of paclitaxel (PAC) were previously developed and characterized. Their chemical stability, in vitro release and pharmacokinetics of PAC were assessed using Taxol (cremophor:ethanol 1:1, 6 mg/ml) as a reference. The shelf-lives of PAC at 25 degrees C in Taxol, LBMW and CMW, in an accelerated stability study, were 71, 57 and 31 days, respectively. The activation energy (Ea) for PAC in Taxol, LBMW and CMW was 23, 16 and 14 kcal/mol, respectively. PAC released from LBMW and CMW using a dialysis technique was significantly slower than that from Taxol. The extents of release of PAC from LBMW and CMW were 25 and 50% of that from Taxol. In vivo pharmacokinetic studies in male Sprague-Dawley rats after IV administration revealed that PAC in LBMW and CMW remained in the systemic circulation five and two times longer and was eight and three times more widely distributed than PAC from Taxol. LBMW and CMW offer a significant clinical advantage in terms of the prolonged half-life and wide tissue distribution, indicating that PAC delivered by these systems intravenously may result in prolonged exposure of PAC to the tumor and subsequently an improved clinical efficacy.     

Stability of benzoyl peroxide in aromatic ester-containing topical formulations

The chemical stability of benzoyl peroxide (BPO) was studied in solutions and gels. The solutions (1% w/v) were prepared in single solvents (alcohol USP, isopropyl alcohol USP, ethyl benzoate, C12-15 alkyl benzoate, dimethyl isosorbide, propylene carbonate, and acetone) and in binary and tertiary combinations of these solvents, with and without the addition of antioxidant(s) (BHT, BHA, eugenol, tert-butyl hydroquinone, Tenox-2, vitamin E, and vitamin C). The solutions were stored at 37 degrees C for 5 weeks, and each week were analyzed for remaining BPO. Using first-order kinetics, the stability of BPO in solution was found to decrease in the order: ternary>binary>single solvent systems. Regardless of the number of solvents present, the highest stability of BPO (t1/2>7.5 weeks) was attained in the presence of ethyl benzoate and C12-15 alkyl benzoate. The stability of BPO in solution did not change significantly with the addition of most antioxidants. The solutions in which BPO remained most stable were one in alcohol USP-ethyl benzoate-C12-15 alkyl benzoate (60:20:20; t1/2=18.15 weeks) and another in alcohol USP-C12-15 alkyl benzoate-isopropanol plus 0.1% BHT (65:20:15; t1/2=12.44 weeks). In turn, these two solutions were converted to homogeneous gels by the addition of Cab-O-Sil. The chemical stability of BPO in these gels was evaluated at 37 degrees, 45 degrees, 50 degrees, and 55 degrees C for 5 weeks. Parallel experiments were conducted with two commercial BPO products, a 2.5% tinted gel and 5% vanishing lotion. BPO was less stable in commercial products (t1/2相似文献   

Stability studies of topical carbonic anhydrase inhibitor 6-hydroxyethoxy-2-benzothiazole sulfonamide.

A new carbonic anhydrase inhibitor, 6-hydroxyethoxy-2-benzothiazole sulfonamide (6-hydroxyethyoxyzolamide), was studied to determine its stability in aqueous solution from pH 2.9 to 9.2 at a constant ionic strength of 0.15 M. This newly synthesized derivative of ethoxyzolamide has demonstrated clinical efficacy for use as an ophthalmic drug to lower intraocular pressure. Drug solution in sealed ampules was placed in a constant temperature over either at two temperatures (75 and 85 +/- 0.2 degrees C) or four temperatures (75, 80, 85, and 90 +/- 0.2 degrees C). Samples were analyzed by known HPLC methods. The results indicated that 6-hydroxyethoxyzolamide is most stable at pH 4 to 5.5. The aqueous drug solutions at pH 7.0 and 8.0 were, nevertheless, sufficiently stable, based on extrapolation of kinetic data at high temperatures using the experimentally determined Arrhenius equation. The degradation compound was identified by spectral analysis to have a hydroxyl group substituting for the original -SO2NH2 group.     

Skin moisturizing effect and skin penetration of ascorbyl palmitate entrapped in solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) incorporated into hydrogel

This study was performed as a complimentary to our previous study regarding the chemical stability of ascorbyl palmitate (AP) in solid lipid nanoparticles (SLN), nanostructured lipid carriers (NLC) and for comparison, in nanoemulsion (NE) incorporated into a hydrogel produced by high pressure homogenization. AP is known as an effective antioxidant that protects tissue integrity similar to vitamin C. Recently, its moisturizing activity in conventional topical formulations was found to be high. The aim of the present study was to investigate the moisturizing potential of AP in SLN and NLC incorporated into hydrogel as colloidal carrier systems. It has been known that SLN and NLC have occlusive effects, but AP incorporation moisturized skin significantly better than placebo in short-term (p < 0.001) and long-term trials (p < 0.01) for both SLN and NLC. In the second part of the study, SLN and NLC were found to sustain the penetration of AP through excised human skin about 1/2 and 2/3 times compared to NE (p < 0.001 and p < 0.01), respectively, due to the solid state of Witepsol E85 in the lipid phase.