Formulation of lyotropic liquid crystal containing mulberry stem extract: influences of formulation ingredients on the formation and the nanostructure.
OBJECTIVE
This study focused on the formulation of lamellar lyotropic liquid crystal (LLC) loaded with mulberry stem extract (MSE).


METHODS
The LLC formulation 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 was PEG-7 glyceryl cocoate/PEG-40 hydrogenated castor oil/glyceryl monooleate. The LLC formation and phase behaviour were observed by polarized optical microscopy (POM) before and after MSE loading. Nanostructure determinations on these formulations following MSE loading used small angle X-ray scattering (SAXS) at 25-40°C.


RESULTS
Lamellar LLCs are formed more easily with n-dodecane than tridecyl salicylate. Propylene glycol, in the aqueous phase (1 : 1), failed to form LLC due to suboptimal critical packing parameter (CPP) value. A single or mixed surfactant system also influenced the formation of lamellar LLC according to the chemical structure of both oils and especially the surfactants used. The four lamellar LLC formulations selected for MSE loading were PEG-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. MSE in F1 and F3 did not affect the lamellar structure, while MSE in F2 and F4 enlarged the lamellar structure. The SAXS data confirmed that the LLC formulations obtained were lamellar and the structure persisted with MSE.


CONCLUSIONS
These lamellar formulations should find widespread application for MSE and perhaps other similar herbal cosmetics.
Department of Pharmaceutical Technology, Faculty of Pharmaceutical Sciences and Center of Excellence for Innovation in Chemistry, Naresuan University, Phitsanulok, 65000, Thailand.
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Yhirayha
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Soontaranon
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Wittaya-Areekul
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Pitaksuteepong
D000473:Alkanes / Q000737:chemistry; D003358:Cosmetics / Q000737:chemistry*; D050866:Liquid Crystals / Q000737:chemistry* / Q000648:ultrastructure; D008859:Microscopy, Polarization; D031625:Morus / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure; D010936:Plant Extracts / Q000737:chemistry*; D018547:Plant Stems / Q000737:chemistry; D053838:Scattering, Small Angle; D013501:Surface-Active Agents / Q000737:chemistry
D000473:Alkanes; D003358:Cosmetics; D010936:Plant Extracts; D013501:Surface-Active Agents; C007548:n-dodecane
formulation; herbal cosmetic; lamellar lyotropic liquid crystal; mulberry stem extract; polarized optical microscopy; small angle X-ray scattering