JOURNAL OF COSMETIC SCIENCE 196 However, 5% concentration was more effective than 1% concentration in providing oxidative stability of cosmetic emulsion at 40°C. Prolonged peroxide formation in emulsion might be a consequence of secondary oxidation product (alkanes, alkenes, alde- hydes, ketones, alcohols, and esters) transformation. Rose extract (1–5%) can be applied in cosmetic emulsions by producers because the extract showed better antioxidant prop- erties than BHT at 5 and 20°C storage (49). It seems that very high protection from oxi- dative stress might be due to the level of carotenoids, as well as phenolic compounds and unsaturation of fatty acids (55). SALI X ALBA (SALICACEAE) Sali x alba L., known as willow bark, is a traditional and folk medicine which has been used for nearly 600 years. The extract of willow bark is composed of salicin-related con- tents, polyphenols, and fl avonoids which are most commonly used therapeutic compo- nents in conditions including pain, fever, infl ammation such as osteoarthritis, headache, tendonitis, and generalized pain (56,57). In cosmetic formulation, this extract has astrin- gent, tonic, and skin-conditioning properties (58). A group of Poland researchers inves- tigated effects of willow bark extracts on oxidative stability in O/W cosmetic emulsions containing wheat germ oil. After evaluation of antioxidant properties of willow bark extract in different concentrations (1 and 5%) exposed to various temperatures and durations of storage, they revealed that both cosmetic emulsions showed good oxidative stability. Actually, the rate of peroxide formation spectrophotometrically measured was slow, and willow bark extract showed more effective antioxidant property at higher concentration (5%) than at lower concentration (1%) at temperatures of 5, 20, and 40°C. There are assumptions that antioxidant capacity of this extract is associated with aforementioned ingredients such as salicin, phenols, and fl avonoids (49). Application of willow extract in cosmetic emulsions can be useful because it showed antioxidant properties and did not show prooxidant activity at both concentrations of 1 and 5%. CONCL USION It be comes the prime responsibility of the cosmetic product manufacturers to provide adequate oxidative stability for long-term storage and safe consumption. Plant extracts rich with antioxidants, especially phenolic compounds, are continuously gaining atten- tion as potential agents, which could protect cosmetic preparations against lipid peroxi- dation processes. This review summarizes all data about plant extracts which could be potentially used for their antioxidant properties in cosmetic emulsions. Investigations conducted so far do not provide complete understanding of the role of plant extracts in improving oxidative stability of formulation because they were mostly focused on moni- toring product stability only at room temperature. Stability testing in elevated tempera- ture storage conditions is certainly required in the future studies to enable wide application of the examined plant extracts in product formulation. Moreover, herbal extracts should be adjusted to a defi ned content of a constituent or a group of substances with known antioxidant activity. Plant extracts appear to be a safe, effi cient, and valuable source of numerous bioactive compounds that might be exploited by pharmaceutical and cos- metic industries.

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