Protective effect of commercial acerola, willow, and rose extracts against oxidation of cosmetic emulsions containing wheat germ oil

The effect of commercial cosmetic plant extracts, acerola, willow, and rose, used at the concentrations of 1 and 5%, and 0.01% butylhydroxytoluene (BHT), on the oxidative stability of oil-in-water (o/w) model emulsions containing 5% of wheat germ oil was studied. Considerable differences in total phenolic and flavonoid contents as well as in the TEAC, FRAP, and DPPH antioxidant activities of extracts were observed. Emulsions were stored at 5 and 20 degrees C for 6 months and at 40 degrees C for 4 weeks. The oxidative stability of emulsions was monitored by the determination of peroxide content. The protective effect of plant extracts or BHT on emulsion oxidative stability was expressed as the protection factor (PF). It was found that all 5% extracts were better antioxidants than BHT in emulsions stored at 5 degrees C. Similar results for 5% willow and rose extracts in emulsions stored at 20 degrees C were obtained. PFs of 5% extracts for emulsions stored at 40 degrees C were 2.4- to 3.5-fold lower than this obtained for BHT. Extracts at the concentration of 1%, with an exception of acerola at 20 degrees C, were also effective as antioxidants in tested emulsions but their PFs were about 1.4-5.7 times lower than those of BHT, depending on extract and storage conditions. Altogether, the results obtained revealed that commercial cosmetic plant extracts can be used at the concentrations recommended by their producers (1 or 5%) as natural antioxidants instead of synthetic BHT. Practical application: The results of the present study can be applied in cosmetic industry to improve the quality and safety of emulsions. The studies on oxidative stability of cosmetic emulsions are an important step in the development of cosmetic product technology as they give information about the shelf-life of product and its optimal storage conditions. The chemical composition of the final product should be optimized over a wide range of temperatures to ensure its physical and oxidative stability because the manufacturer is not able to predict conditions under which the cosmetics will be stored by consumers. Higher concentrations (1-5%) of plant extracts in cosmetic emulsions can be applied by the producers to improve not only the physicochemical properties of product, but as multifunctional, skincare cosmetic ingredients.