[Glycol plant extracts in the prescription of topical skin-whitening hydrogels]. / Zastosowanie glikolowych wyciagów roslinnych w recepturze hydrozeli o dzialaniu wybielajacym podawanych na skóre.

An attempt was made to produce and test, according to the guidelines of Polish Pharmacopeia VIII, new prescriptions of hydrogels which could be applied in the treatment of skin diseases associated with hyperpigmentation. Hydrogel formulations containing a substance of skin-whitening activity (arbutin) and glycol plant extract was produced on Carbopol Ultrez 10 base. Two glycol plant extracts of confirmed beneficial effect on skin were selected: an extract of ginkgo leaves and of rosemary. For comparative purposes also preparations with arbutin were produced in which propylene glycol was introduced instead of glycol plant extracts. The assumption of the carried out study was to investigate physicochemical properties of model formulations, estimation of arbutin pharmaceutical availability from the suggested formulations and the assessment of the effect of glycol plant extract components on the process of arbutin diffusion from the produced hydrogel formulations. The formulation viscosity parameters were determined using cone-plate digital rheometer. Gravimetric method was applied to estimate the kinetics of volatile components from the preparations. Potentiometric method was used to measure pH. The rate of arbutin release through a semipermeable membrane to the acceptor fluid was tested in vitro. Spectrophotometric method was used for the determination of the quantity of the released therapeutic substance at defined time intervals. All the proposed formulations are viscoelastic systems having yield stress. There is a strict dependence between rheological properties characterizing the tested hydrogels and the quantity of the arbutin released from them. The process of arbutin release to the acceptor fluid through a semipermeable membrane was most effective from the formulation containing glycol extract of ginkgo (F1A+M).