Abstract
The aim of the paper is to test stability and biophysical properties of hydrophilic and lipophilic emulsions with selected vegetable seed oils: Limnanthes alba, Prunus amygdalus dulcis, Cannabis sativa, Rosa rubiginosa and Hellianthus annuus. Biophysical properties of emulsions are investigated in vivo using non-invasive instrumental methods (corneometry, tewametry and pH) in a group of 12 healthy women volunteers. Their stability profiles (colour, phase separation and centrifugation) under various temperatures (9, 25, 37 and 57 °C) and storage time (24 hours, 2, 7, 14, 21 and 28 days) were monitored. The moisturising activities of the emulsions supplemented with various oils were comparable. The lipophilic emulsions showed a better ability to improve the condition of the skin barrier due to formation of a surface lipid film. The tested formulations regulated the pH of the skin towards neutral values. Lipophilic emulsions showed earlier phase separation and changes in colour. The greatest resistance to thermal stress during storage was observed for the emulsion bases. Emulsions containing oils, except for those with rosehip and hempseed oils, were stable up to the temperature of 37 °C. The studied emulsion systems are excellent vehicles of vegetable oils and exhibit relatively good stability, benefiting the natural properties of skin.
Highlights
Emulsions are some of the most widespread forms of cosmetic and pharmaceutical preparations
The findings presented in this study show that hydrophilic and lipophilic emulsion with vegetable oils exhibit good stability and biophysical characteristics
The base emulsion and most of the tested formulations containing vegetable oils did not destabilize at storage temperatures of up to 37 °C
Summary
Emulsions are some of the most widespread forms of cosmetic and pharmaceutical preparations. Emulsion is defined as a heterogeneous dispersion system of two immiscible liquids or liquids with limited miscibility, one of which being the dispersion part in the form of minute particles in the liquid environment of the other given liquid. In order to produce emulsions suitable for practical use, emulsifiers must be present. These are surface active agents that prevent degradation of the whole system (Imhof, Pine, 1997; Masmoudi et al, 2005). Various methods for disrupting stability are available, for example, creaming and sedimentation are based on gravity separation. In both cases it is possible to observe gradual separation with the naked eye. Stability is a fundamental issue for the lifetime of an emulsion, or more precisely varied preparations, as any separation of components renders the given product unusable
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