Formulation of lyotropic liquid crystal containing mulberry stem extract: influences of formulation ingredients on the formation and the nanostructure

SynopsisObjectiveThis study focused on the formulation of lamellar lyotropic liquid crystal (LLC) loaded with mulberry stem extract (MSE).MethodsTheLLCformulation tested used two oils: n‐dodecane or tridecyl salicylate, a co‐solvent (propylene glycol) and a single (PEG‐7 glyceryl cocoate) or mixed surfactant system. The mixed surfactant wasPEG‐7 glyceryl cocoate/PEG‐40 hydrogenated castor oil/glyceryl monooleate. TheLLCformation and phase behaviour were observed by polarized optical microscopy (POM) before and afterMSEloading. Nanostructure determinations on these formulations followingMSEloading used small angleX‐ray scattering (SAXS) at 25–40°C.ResultsLamellarLLCs are formed more easily with n‐dodecane than tridecyl salicylate. Propylene glycol, in the aqueous phase (1 : 1), failed to formLLCdue to suboptimal critical packing parameter (CPP) value. A single or mixed surfactant system also influenced the formation of lamellarLLCaccording to the chemical structure of both oils and especially the surfactants used. The four lamellarLLCformulations selected forMSEloading werePEG‐7 glyceryl cocoate/tridecyl salicylate/water; mixed surfactant/tridecyl salicylate/water;PEG‐7 glyceryl cocoate/n‐dodecane/water and mixed surfactant/n‐dodecane/water, named F1, F2, F3 and F4, respectively.MSEin F1 and F3 did not affect the lamellar structure, whileMSEin F2 and F4 enlarged the lamellar structure. TheSAXSdata confirmed that theLLCformulations obtained were lamellar and the structure persisted withMSE.ConclusionThese lamellar formulations should find widespread application forMSEand perhaps other similar herbal cosmetics.