Vitamin E-loaded bigels and emulsions: Physicochemical characterization and potential biological application.

Bigels have been studied as topical formulations for its benefits over sensory and drug delivery parameters. However, there is still few evidences about the properties of the combination of organogelators, oily phases and bioactive molecules into rheological and stability behavior. We investigated the use of classical organogelators (candelilla wax and 12-hydroxystearic acid) and oily phases (sunflower and mineral oil) in 5/95 organogel/polymeric hydrogel ratio to compare vitamin E bigels with its corresponding emulsions. The rheological measurements, microstructure, physical and oxidative stability properties and biological behavior were evaluated. The obtained oil-in-water bigels and emulsions showed crystallization pattern at the interface with high thermal and centrifuge-stress stability. Viscoelastic weak gels were obtained with higher thixotropy and consistency of 12-hydroxystearic bigels. The diameter of the inner phase was increased by vitamin E, despite its little influence over physical and oxidative stability of bigels and emulsions. Those findings indicated that sensory attributes may be regulated by the organogel composition.

Coumaric acid derivatives as tyrosinase inhibitors: Efficacy studies through in silico, in vitro and ex vivo approaches.

p-Coumaric acid is a known inhibitor of tyrosinase, an enzyme involved in the initial steps of the melanin synthesis in human and other species. However, its low lipophilicity impairs its penetration through skin and efficacy as antimelanogenic agent indeed. Accordingly, this paper reports the assessment of several coumaric acid derivatives as tyrosinase inhibitors and antimelanogenic agents in in vitro, in silico and ex vivo assays. The compounds were designed with modifications in the aromatic and acid moieties of p-coumaric acid, being the coumarate esters the most promising derivatives. The compounds showed higher tyrosinase inhibitory activity (pIC50 3.7-4.2) than the parent acid, being compounds 1d, 1e and 1f the most potent inhibitors. Docking analysis showed that these esters are competitive inhibitors per se, and act independently of a redox mechanism as suggested by DPPH assays. Moreover, the esters showed efficacy in reducing the melanin deposition in human skin fragments at 0.1% concentration, especially compound 1e. In summary, there is an important equilibria between tyrosinase affinity and lipophilicity that must be considered to get effective antimelanogenic agents with adequate permeability in the skin.