Development of paraben-free hydrogel based on plant extracts for topical application

Historically, medicinal preparations are derived from plants and their employment in dermatological and cosmetic products is increasing [1]. Topical application of products containing compounds with free radical scavenging properties protects tissues from oxidative damage [2]. The skin is an important protective barrier between the environment and the inner milieu, being highly exposed to oxidative stress, either from exogenous as well as endogenous sources [3]. The antioxidant potential of herbal extracts or pure isolated compounds have been extensively studied, but very few reports are available on the antioxidant properties of final formulations in which they have been included. In the present study, aqueous and ethanolic extracts from the flower buds of hawthorn (Crataegus monogyna Jacq.) were incorporated into hydrosoluble gels. Gels have been largely used in cosmetic products and as a dermatologic base, as they are easily dispersed, nonoily and can carry hydrosoluble active principles. Gel consistency was optimized when carbopol 940 was added at 1%. The prepared formulations presented a light green colour, a non-greasy texture and were promptly absorbed by the skin. Since the inclusion of parabens is nowadays poorly accepted by the consumers, imidazolidinyl urea was included as the antimicrobial component. Regarding pH evaluation, there were no significant alterations during the 90 days of observation, with values ranging between 5.5 and 6.5. The antioxidant activity of the prepared hydrogels was assessed and compared with a blank formulation (with all the components used in the hydrogel formulation, except the extract) and also with the results obtained for the extracts alone, at the same concentration (1 00 jlg/ml). The antioxidant activity measured in each hydrosoluble gel is very close to the value obtained for the isolated extract, in what regards inhibition of lipid peroxidation using thiobarbituric acid reactive substances (TBARS) and Beta carotene bleaching inhibition, 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity and reducing power. Hydrogels prepared with ethanolic extracts showed higher antioxidant activity than aqueous extracts, unless in Beta carotene bleaching inhibition assay. In general, it became evident that the inclusion of extracts in the prepared hydrosoluble gels caused very limited losses in their bioactivity.