1,721,047 research outputs found
Photo-stabilization of butyl methoxydibenzoylmethane by encapsulation in lipid microparticles
No full textThe sunscreen agent, butyl methoxydibenzoylmethane (BMDBM), one of the most widely used UVA (320-400 nm) filter, undergoes degradation under sunlight exposure, which is a limiting factor on its overall performance. This study reports on the incorporation of BMDBM into solid lipid microparticles as a strategy to reduce the sunscreen photoinstability. The microparticles were produced using various lipid materials (tristearin, glyceryl behenate, stearic acid) and hydrogenated phosphatidylcholine as the surfactant. The efficacy of the lipid microparticles was evaluated after their introduction in a model cream. The light-induced decomposition of BMDBM was reduced from 33.8% to 15.8% by its incorporation into the lipid microparticles. Moreover, the encapsulation process did not alter the UVA protection provided by the sunscreen agent
Bile acid separation
No full textA review of the methods available for the separation of bile acids is presented, highlighting the most recent developments. The major chromatographic techniques (TLC, GC, HPLC) and combined detection systems for the determination of bile acids are critically evaluated and their advantages and disadvantages discussed. Moreover, future directions in which progress might occur are also indicated. Capillary GC-MS is the more established method since it provides higher efficiency combined with greater sensitivity and specificity and has proven crucial in identifying unusual bile acids. However, it requires deconjugation and derivatization and hence the conjugated species must be inferred from the initial isolation procedure. HPLC is directly amenable to the different forms of bile acids, but it suffers from insufficient resolving power which can be enhanced by exploiting the mobile-phase selectivity. The development of HPLC detection systems with higher sensitivity and specificity than conventional HPLC-UV is reported. In particular, methods for the direct coupling of HPLC to MS are examined with special emphasis on soft ionization processes (thermospray, fast atom bombardment, ion spray). Finally, the analytical potential for bile acid assays of more recent techniques including supercritical fluid chromatography and capillary electrophoresis is evaluated
Coloading of a photostabilizer with the sunscreen agent, butyl methoxydibenzoylmethane in solid lipid microparticles
No full textThe sunscreen agent, butyl methoxydibenzoylmethane (BMDBM), one of the most widely used UV-A filter, undergoes decomposition under sunlight exposure, which is a limiting factor on its overall performance. To reduce the sunscreen photodegradation, this study investigates the incorporation into solid lipid microparticles (SLMs) of BMDBM together with the photostabilizer, 4-methylbenzylidene camphor (MBC). The microparticles were produced by the melt dispersion technique using various lipid materials (tristearin, glyceryl behenate, and stearic acid) and hydrogenated phosphatidylcholine as the surfactant. The highest retention capacity for BMDBM and MBC was achieved with tristearin microparticles. These SLMs were characterized by scanning electron microscopy and powder X-ray diffraction analyses. The BMDBM and MBC loading was 10.4 and 10.1%, respectively. The efficacy of the SLMs was evaluated after their introduction in a conventional cream (oil-in-water emulsion). The light-induced decomposition of BMDBM was decreased by encapsulation into the SLMs (the extent of degradation was 33.8 ± 5.5% for unencapsulated BMDBM/MBC and 25.3 ± 4.2% for BMDBM-loaded microparticles in conjunction with free MBC). Moreover, the co-loading of the MBC stabilizer in the SLMs produced a further reduction of the photodegradation of the UV-A filter (the BMDBM loss was 16.9 ± 5.9%) compared with the microparticles containing BMDBM without MBC. Therefore, incorporation in lipid microparticles of BMDBM together with the MBC photostabilizer is more effective in enhancing the UV-A filter photostability than the SLMs loaded with BMDBM alone
Incorporation of quercetin in lipid microparticles:Effect on photo- and chemical-stability
No full textLipid microparticles loaded with the flavonoid, quercetin were developed in order to enhance its stability in topical formulations. The microparticles were produced using tristearin as the lipid material and phosphatidylcholine as the emulsifier. The obtained lipoparticles were characterized by release studies, scanning electron microscopy and powder X-ray diffractometry. The quercetin loading was 12.1% (w/w). Free or microencapsulated quercetin was introduced in a model cream formulation (oil-in-water emulsion) and irradiated with a solar simulator. The extent of photodegradation was measured by high-performance liquid chromatography. The light-induced decomposition of quercetin in the cream vehicle was markedly decreased by incorporation into the lipid microparticles (the extent of degradation was 23.1 ± 3.6% for non-encapsulated quercetin compared to 11.9 ± 2.5% for the quercetin-loaded microparticles) and this photostabilization effect was maintained over time. Moreover, the chemical instability of quercetin, during 3-month storage of the formulations at room temperature and in the dark, was almost completely suppressed by the lipid microparticle system. Therefore incorporation of quercetin in lipoparticles represents an effective strategy to enhance its stability in dermatological products
Use of cyclodextrin to enhance the safety and efficacy of sunscreen agents
No full textThe present report describes our studies on the influence of cyclodextrin complexation on the photodegradation and percutaneous permeation of some of the most commonly used UV filter
Monitoring and Quality Control of Sunscreen Photostability
No full textEvaluation of the photochemical stability of sunscreen preparations is of paramount importance for the development of UV absorbers and for the quality control of finished suncare products. The basic components of the photostability test ( irradiation source, sample support, sample type and analytical technique to evaluate the extent of degradation) have been described and discussed with relation to their advantages and disadvantages
Comparative evaluation of different substrates for the in vitro determination of sunscreen photostability: spectrophotometric and HPLC analyses
No full textSynopsis Polymethylmethacrylate (PMMA) plates and TransporeTM tapes were compared as substrates for the in vitro evaluation of photostability of commercial sunscreen products. The sun care preparations were applied respectively on TransporeTM tapes and PMMA plates and their sun protection factors (SPF) and UVA protection parameters [UVA/UVB ratio, critical wavelength, UVA protection factor (UVA-PF)] were measured by transmission spectroscopy, before and after irradiation with simulated sunlight. No significant differences were observed in the UV protection parameters measured on TransporeTM tapes or PMMA plates, before exposure to the solar simulator. Conversely, after irradiation, the SPF values of the sun care products exhibited marked variations between the two substrates, the decrease in SPF being greater on PMMA plates (31.3-63.1%) than on TransporeTM tapes (10.4-23.8%). Differences between the two substrates were detected also for the UVA protection parameters, although they were significant only for the UVA-PF. The tested samples were assayed also by high-performance liquid chromatography (HPLC) to assess the extent of photodegradation of the UV filters present in the examined formulations. The results showed that for the PMMA plates, the light-induced decrease in SPF, as determined by spectrophotometry, fitted well with the percentage loss of ethyl hexyl methoxycinnamate (the only photounstable UVB filter present) measured by HPLC. Moreover, for the PMMA substrate, the UVA-PF percentage reduction was consistent with the percentage degradation of butyl methoxydibenzoylmethane (the only photounstable UVA filter present) determined by HPLC. On the other hand, poor correlation between spectrophotometric and HPLC analyses was observed on TransporeTM tapes. Therefore, PMMA plates are more reliable than TransporeTM tapes as substrates for in vitro photodegradation tests of sunscreen products by transmission spectroscopy. © 2009 Society of Cosmetic Scientists and the Société Française de Cosmétologie
Influence of cyclodextrins on in vitro human skin absorption of the sunscreen, butyl-methoxydibenzoylmethane
No full textThe effects of hydroxypropyl- b-cyclodextrin (HP- b-CD) and sulfobutylether- b-CD (SBE7- b-CD) on in vitro human skin penetration and retention of the sunscreen agent butyl-methoxydibenzoylmethane (BM-DBM) were investigated. The interaction between the UV filter and the cyclodextrins was studied in water by phase-solubility analysis. Solid complexes were prepared by the co-evaporation method and characterized by NMR spectroscopy, thermal analysis and powder X-ray diffraction. Solutions containing BM-DBM free or complexed with cyclodextrins were applied to excised human skin in Franz diffusion cells and the amount of sunscreen permeated after 6 h into the stratum corneum, viable epidermis, dermis and receptor fluid was assessed by HPLC. As much as 14.10–16.78% of the applied dose of BM-DBM penetrated within the skin tissue. No sunscreen was detected in the dermis and in the receiver phase. The greater proportion (84.6–95.5%) of the absorbed UV filter was localized in the stratum corneum with no significant differences between uncomplexed or complexed BM-DBM. Notable levels (2.29% of the applied dose) of the sunscreen agent accumulated in the epidermis from the preparation containing free BM-DBM. The epidermal concentration of the UV filter was markedly reduced (0.66% of the applied dose) by complexation with SBE7- b-CD, whereas HP- b-CD had no effect. The decreased BM-DBM retention in the epidermal region achieved by SBE7- b-CD limits direct contact of the sunscreen and of its reactive photolytic products with the skin viable tissues
In vivo human skin penetration of the UV filter ethylhexyl triazone: Effect of lipid microparticle encapsulation
No full textBackground/Aims: The data available on the skin permeability of ethylhexyl triazone (EHT), a widely used high-molecular-weight (823.1-Da) UV filter, are scarce and obtained only via in vitro studies. Therefore, we evaluated in vivo the penetration of EHT in human stratum corneum by the tape stripping technique. Moreover, the effect of EHT encapsulation in lipid microparticles (LMs) on its diffusion through the stratum corneum was examined. Methods: LMs loaded with EHT were prepared using glyceryl behenate and phosphatidylcholine. Creams containing EHT free or encapsulated in LMs in conjunction with the two most commonly used UV filters, octyl methoxycinnamate (OMC) and butyl methoxydibenzoylmethane (BMDBM), were applied to human volunteers and the fraction of the applied sunscreen dose having penetrated into different stratum corneum layers was measured. Results and Conclusion: For the cream with the nonencapsulated sunscreen agent, the percentage of the applied EHT dose diffused into the stratum corneum was 21.9 ± 4.9%, not significantly different from that of the smaller-molecular-weight OMC (22.2 ± 7.6%) and BMDBM (20.5 ± 3.7%). A marked (45.7%) and statistically significant reduction in the in vivo skin penetration of EHT was attained with the cream containing microencapsulated EHT. The decreased percutaneous penetration provided by the LMs should favor the efficacy of EHT and limit potential toxicological risks
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