ascorbic-acid and dicetylphosphate

Lycopene, a lipophilic carotenoid, has been known as an effective antioxidant in supporting the cutaneous defensive system. However, it is unstable when exposed to light and water. In this study, lycopene was isolated from tomatoes and a vesicular delivery system was developed to entrap and stabilize the lycopene in the aqueous system. A simple process, maceration in ethyl acetate, was used to extract lycopene from the tomatoes. The extract was then chromatographed on the Sephadex LH20 column using acetone as a solvent system to yield 995 μg of lycopene per gram of dried tomato weight. The vesicular delivery system was prepared from a combination of ascorbic acid-6-palmitate (AP), cholesterol and dicetyl phosphate using a thin film hydration method. The formulation was composed of AP, cholesterol and dicetyl phosphate at a 44:44:12 molar ratio and with 2.12 μmol/ml of the isolated lycopene. Both blank vesicles and lycopene loaded vesicles were kept for a period of 3 months at 4±2°C and at the room temperature (28±2°C) to evaluate the effect of the encapsulation on the characteristic of the vesicles and on the antioxidant activity of the encapsulated lycopene. The result implied that lycopene could be stabilized in the vesicles and its scavenging activity against DPPH free radicals was superior to that of the free lycopene solution.

Topics: Antioxidants; Ascorbic Acid; Carotenoids; Cholesterol; Chromatography, High Pressure Liquid; Drug Delivery Systems; Drug Stability; Free Radical Scavengers; Lycopene; Organophosphates; Solanum lycopersicum; Temperature; Time Factors; Water

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.

Topics: Animals; Ascorbic Acid; Dimyristoylphosphatidylcholine; Drug Delivery Systems; Electric Stimulation; Hydrogel, Polyethylene Glycol Dimethacrylate; In Vitro Techniques; Liposomes; Male; Organophosphates; Poloxamer; Rats; Rats, Sprague-Dawley; Skin; Skin Absorption

Vesicles with biological activity or with a targeting function in addition to carrier properties will have an added advantage. Vesicles prepared with amphiphiles having antioxidant property may have potential applications towards disorders implicated with reactive oxygen species. Ascorbyl palmitate (ASP) was explored as bilayer vesicle forming material. It formed vesicles (Aspasomes) in combination with cholesterol and a negatively charged lipid (dicetyl phosphate). Aspasomes were prepared by film hydration method followed by sonication in which aqueous azidothymidine (AZT) solution was encapsulated in aqueous regions of bilayer. Aspasomes were obtained with all compositions containing 18-72 mol% cholesterol. Differential scanning calorimetric data of aspasome dispersion and anhydrous mixtures of ascorbyl palmitate, cholesterol and dicetyl phosphate confirm the formation of bilayered vesicles with ascorbyl palmitate. Cholesterol content in aspasome did not exhibit any relation with vesicle size, zeta potential or percent entrapment. A substantial change in release rate of azidothymidine from aspasome was noticed on varying the proportion of cholesterol. Release rate and cholesterol content in Aspasomes did not exhibit any relation. A preparation with 45 mol% of cholesterol showed maximum retardation in release rate, than other compositions. The change in capture volume with time (latency) was studied for 8 h and with such a short duration study it was difficult to predict long term stability of these vesicles. But release experiments do indicate stability up to 18 h. Percent reducing activity of aspasome was estimated by measuring the absorbance of alpha,alpha-diphenyl-beta-picrylhydrazyl (DPPH) at 517 nm after addition of test antioxidant samples. These studies revealed that the antioxidant potency of ascorbyl moiety is retained even after converting ascorbyl palmitate into vesicles (Aspasomes). The antioxidant potency of Aspasomes was assessed by measuring the protection offered by this preparation against quinolinic acid induced lipoperoxidation of whole human blood in vitro, where in the lipoperoxidation was monitored by measuring thiobarbituric acid reactive substances (TBARS) levels. Aspasome rendered much better antioxidant activity than ascorbic acid. Transdermal permeation of aspasomal AZT, ASP-AZT aqueous dispersion and AZT-solution across excised rat skin was investigated in vitro using Franz diffusion cell. Permeation of aspasomal AZT was much

Topics: Animals; Antioxidants; Ascorbic Acid; Calorimetry, Differential Scanning; Chemistry, Pharmaceutical; Cholesterol; Drug Carriers; Drug Stability; In Vitro Techniques; Lipid Bilayers; Lipid Peroxidation; Organophosphates; Particle Size; Rats; Skin Absorption; Solubility; Zidovudine

A chemically modified electrode based on the carbon nanotube film-coated glassy carbon electrode (GCE) is described for the simultaneous determination of dopamine (DA) and serotonin (5-HT). The multiwall carbon nanotube (MWNT) film-coated GCE exhibits a marked enhancement effect on the current response of DA and 5-HT and lowers oxidation overpotentials. The responses of DA and 5-HT merge into a large peak at a bare GCE, but they yield two well-defined oxidation peaks at the MWNT film-coated GCE. The experimental parameters were optimized, and a direct electrochemical method for the simultaneous determination of DA and 5-HT was proposed. The interference of ascorbic acid (AA) was investigated, and the results showed that a large excess of AA did not interfere with the voltammetric responses of DA and 5-HT. The modified electrode has been successfully applied for the assay of 5-HT and DA in human blood serum.

Topics: Adsorption; Ascorbic Acid; Carbon; Dopamine; Electrochemistry; Electrodes; Humans; Hydrogen-Ion Concentration; Nanotechnology; Nanotubes, Carbon; Organophosphates; Oxidation-Reduction; Reproducibility of Results; Serotonin; Uric Acid