Elevations were observed in log P for Strat-M™ with an increase in the log Ko/w of the applied compounds, and similar results were observed with the human and hairless rat skins. A correlation was obtained in log P values between Strat-M™ and human or hairless rat skin. Furthermore, the diffusion and partition parameters of chemicals in Strat-M™ were similar to those in the excised human and rat skins. These results suggest that Strat-M™ could be used as an alternative to animal or human skin in permeation studies.

Topical formulations are not always suitable to deliver active ingredients to large areas of skin. Thus, in this study, we aimed to develop an oral formulation for skin tissue targeting with a high bioavailability using liquid crystal (LC) dispersions comprising cubosomes of a mal-absorptive model compound, p-amino benzoic acid (PABA), which is an active element in cosmeceuticals, dietary supplements and skin disorder medicines. The bioavailability and skin concentration of PABA were investigated after oral administration in rats. The effect of the remaining amount of the LC formulation in the stomach on the pharmacokinetic profiles of orally administered PABA was evaluated. The skin permeation and concentration of PABA were also investigated using an in vitro permeation experiment. As a result, the bioavailability of PABA was significantly improved by administration of PABA-LC formulations compared with PABA solution alone, although the effect was greatly influenced by the type of LC-forming lipids. The in vitro skin permeation study showed that the PABA concentration in the skin when applied from the dermis side was higher than when applied from the epidermis side. These findings suggested that oral administration advantageously supports skin targeting, and oral LC formulations could be a promising material in cosmeceutical, dietary and clinical fields.

Skin concentrations of topically administered compounds need to be considered in order to evaluate their efficacies and toxicities. This study investigated the relationship between the skin permeation and concentrations of compounds, and also predicted the skin concentrations of these compounds using their permeation parameters. Full-thickness skin or stripped skin from pig ears was set on a vertical-type diffusion cell, and lidocaine (LID) solution was applied to the stratum corneum (SC) in order to determine in vitro skin permeability. Permeation parameters were obtained based on Fick's second law of diffusion. LID concentrations at each depth of the SC were measured using tape-stripping. Concentration-depth profiles were obtained from viable epidermis and dermis (VED) by analyzing horizontal sections. The corresponding skin concentration at each depth was calculated based on Fick's law using permeation parameters and then compared with the observed value. The steady state LID concentrations decreased linearly as the site became deeper in SC or VED. The calculated concentration-depth profiles of the SC and VED were almost identical to the observed profiles. The compound concentration at each depth could be easily predicted in the skin using diffusion equations and skin permeation data. Thus, this method was considered to be useful for promoting the efficient preparation of topically applied drugs and cosmetics.

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This study investigated the possibility of inhibition of the SARS-CoV-2 virus using the compounds alpha-Boswellic acid (ABA) and beta-Boswellic acid (BBA) which are active components in the well-known natural product Boswellia carterii (BC). The SARS-CoV-2 virus reproduces in the body by linking its spike with the cell receptor. At the same time, a pH range (4.5-6) of the cell's lysosomes is considered as a perfect environment to release RNA in the cell cytoplasm. In view of these, docking studies were employed to study the interaction between the spikes of the virus and ABA or BBA using Molecular Graphic Laboratory (MGL) tools and AutoDock Vina application. The binding of the ABA and BBA with the spike of the virus could inhibit its reproduction or provide sufficient time for the immune system to recognize the virus and hence, produce suitable antibodies. In addition, the pKa of ABA, BBA and hydroxychloroquine (HCQ) were calculated using HF/6-311G (d,p) method and then they were compared with the experimental pKa of HCQ. The Lethal Concentrations (LC50) of ABA and BBA were also calculated. In addition, molecular electrostatic potential is reported which indicates the active sites of ABA and BBA.