2016 Volume 16 Issue 7 Pages 337-344
Tranexamic acid cetyl ester hydrochloride (TXC), which is synthesized by chemically modifying the tranexamic acid with the hydrophobic C16-chain, is utilized as an active ingredient in cosmetics. The chemical structure results in the higher hydrophobicity than water-soluble tranexamic acid which accelerate percutaneous absorption through stratum corneum. Although TXC was designed for the sake of the transdermal permeability to enhance bioavailability, we are interested in its structure as cationic amphiphile. Binary mixtures at different compositions showed a variety of self-assembling structures. Comparing with the general cationic surfactant systems, the TXC/water system showed highly organized orientation of liquid crystal, the higher Krafft temperature, and the lower critical micellar concentration due to its strong inter-molecular interaction between cyclohexyl groups which is a rigid six-membered ring conformation in the molecule. Upon addition of a long-chain alcohol, furthermore, α-gel can be formed. We also observed a unique α-gel phase consisting of dual channels in the quaternary water/TXC/cetyl alcohol/batyl alcohol system, named “Bicontinuous Alpha-Gel (BAG)”, which is beneficial for emulsification of various oils. In this review, we interpret the physicochemical properties of TXC and the hierarchical structure of α-gel, and introduce cosmetic performance of the α-gel formulation such as skin permeation of TXC and sensory effect.
