Analysis of in vitro release through reconstructed human epidermis and synthetic membranes of multi-vitamins from cosmetic formulations

A convenient method for in vitro investigation of the release of lipid- and water-soluble vitamins from cosmetic formulations was developed. The permeation of (d)-α-tocopherol (vitamin E), retinyl acetate (pro-vitamin A), ascorbic acid (vitamin C) and pyridoxine (vitamin B6) through SkinEthic^® reconstructed human epidermis (RHE), and synthetic polyethersulfone and polycarbonate membranes was studied in vitro using a Franz-type diffusion apparatus, coupled either to a spectrophotometer for continuous reading (dynamic setting) or to HPLC-DAD analysis of the receptor medium (static setting). O/W and W/O emulsions were compared with simple aqueous solutions for their kinetic of vitamins release, to evaluate the influence of the cosmetic formulation on the bioavailability of active ingredients. Results indicate that synthetic membranes offer a limited barrier to the diffusion of vitamins, but may provide information on the release ability of the formulation. Penetration was more effective when water was the external phase of the formulation, i.e. W/O emulsions were less effective in the release of vitamins than O/W emulsion or aqueous solutions. RHE (17 days old) offered a significantly higher barrier to penetration of vitamins, as expected for native human epidermis. The relative ranking in coefficient of permeability (Ps (cm/h)) was: ascorbic acid > pyridoxine ? retinyl acetate > α-tocopherol ∼0, the absolute values depending on the formulation. The method herein described showed to be a practical and convenient tool for the quality-control and efficacy evaluation of cosmetic formulations.     

Development and validation of a GC/IT-MS method for simultaneous quantitation of para and meta-synephrine in biological samples

After the FDA's ban of ephedrine-containing supplements, Citrus aurantium appeared as an alternative to ephedra in herbal weight loss products. Synephrine, the most abundant active component of C. aurantium, exists in three different structural or positional isomeric forms (ortho—o-, meta—m-, and para—p-). Dietary supplements contain m- and p-synephrine, both α-adrenergic agonists,while the m-isoform is the most potent at α₁-adrenoreceptors. In spite of the pharmacokinetic and toxicological interest in the study of these compounds, adequate methods for their quantification in biological samples are yet to be developed. Thus, in the present study, a sensitive gas chromatography–ion trap mass spectrometry (GC/IT-MS) method was developed and validated for the simultaneous quantitation of m- and p-synephrine in a cellular matrix after solid phase extraction (SPE). The validation of the method was performed through the evaluation of the following parameters: selectivity, linearity, specificity, precision, accuracy, limit of detection, limit of quantification, and recovery. The method's applicability was studied in two different biological matrices by evaluating p- and m-synephrine uptake in Caco-2 cells and also in freshly isolated cardiomyocytes from adult rat. The developed GC/IT-MS method was shown to be selective, accurate, precise, and valid for simultaneous determination of p- and m-synephrine in biological samples.