Characterization and shelf life of β-carotene loaded solid lipid microparticles produced with stearic acid and sunflower oil

Solid lipid microparticles were tested as microencapsulation systems for protecting β-carotene from degradation. Blends of long-chain (C18) solid lipids (70% stearic acid) and sunflower oil (30%) were used to produce lipid microparticles encapsulating the carotenoid. Polysorbate 80 (4%) was employed to stabilize the stearic acid microparticles. The concentration of β-carotene was monitored using spectrophotometry, the particle size distribution was measured by laser diffraction, the crystal structure was determined by wide angle X-ray diffraction (WAXD), and the thermal behaviour was characterized by differential scanning calorimetry (DSC) over a period of seven months. All of the systems had an average particle size smaller than 5 µm. To avoid β-carotene oxidation, α-tocopherol was added to the formulations and its action as an oxygen trap was crucial for the antioxidant effect. For stearic-acid microparticles with a-tocopherol, more than 90% of the initial amount of β-carotene was preserved after seven months under refrigerated storage (7-10°C) in the dark. Significant microstructural alterations were detected using WAXD and DSC only in the stearic acid microparticles without alpha-tocopherol. These results seemed promising and suggested that the blends of long-chain solid lipids and liquid lipids were suitable for the production of stable solid lipid microparticles.

Analysis of in vivo absorption of didanosine tablets in male adult dogs by HPLC / 药物分析学报

Didanosine is an effective antiviral drug in untreated and antiretroviral therapy-experienced patients with Human Immunodeficiency Virus (HIV).An automated system using on-line solid extraction and High performance Liquid Chromatography (HPLC) with ultraviolet (UV) detection was developed and validated for pharmacokinetic analysis of didanosiae in dog plasma.Modifications were introduced on a previous methodology for simultaneous analysis of antiretroviral drugs in human plasma.Extraction was carried out on C18 cartridges,with high extraction yield as stationary phase,whereas mobile phase consisted of a mixture of 0.02 M potassium phosphate buffer,acetonitrile (KH2PO4:acetonitrile:96∶4,v/v) and 0.5％ (w/v) of heptane sulphonic acid.The pH was adjusted to 6.5 with triethylamine.All samples and standard solutions were chromatographed at 28℃.For an isocratic run,the flux was 1.0 mL/min,detection was at 250nm and injected volume was 20μL.The method was selective and linear for concentrations between 50 and 5000 ng/mL.Drug stability data ranged from 96％ to 98％,and limit of quantification was 25 ng/mL.Extraction yield was up to 95％.Drug stability in dog plasma was kept frozen at -20℃ for one month after thee freeze-thaw cycles,and for 24 h after processing in the auto sampler.Assay was successfully applied to measure didanosine concentrations in plasma dogs.