[The effect of dry standardized plant extracts on the process of arbutin release from topical preparations produced on Carbopol base].

An attempt was made to estimate the effect of plant extract components (nettle extract, sage extract) on the process of arbutin release from new prescriptions of skin-bleaching gels. Formulations containing arbutin and dry standardized plant extracts were produced for this purpose. The suggested hydrogel vehicles were prepared on the base of two polymers: Carbopol Ultrez 10 and Noveon AA-1. The preparations were subjected to physicochemical tests. Viscosity parameters were determined using cone-plate digital rheometer. Potentiometric method was used to measure pH of the produced hydrogels. The rate of arbutin release through a semipermeable membrane to the acceptor fluid was tested in vitro. The rate of the process of release was determined at defined time intervals by spectrophotometric method. The effect of plant extract components on arbutin process of diffusion was estimated. The highest pharmaceutical availability of arbutin was obtained for hydrogels on Noveon AA-1 base with dry sage extract (F2-A+Sz). The area under the curve of arbutin release from this hydrogel was 25,94 c.u. The arbutin content in the last sample collected during the test of its release was 5,6509 mg/cm2 of the area of release. There were also obtained beneficial applicative rheological parameters, such as: low structural viscosity value (31497 mPa x s at shear rate 2,01 l/s) and yield stress (22,9 N/m2) for F2-A+Sz formulation. All tested formulations demonstrated rheological stability and high pharmaceutical availability after six months of storage.