Antioxidant capacity of the extracts from flowers of Erica australis L.: Comparison between microwave hydrodiffusion and gravity (MHG) and distillation extraction techniques - Formulation of sunscreen creams

Abstract

Microwave hydrodiffusion and gravity (MHG) extraction of Erica australis flowers was optimized evaluating different microwave irradiation powers (25−200 W). Collected extracts were compared with the liquid phase obtained by conventional distillation. Their total phenolic content, antioxidant capacity and color features were evaluated. Microscopical properties of the flower tissues allowed assessing the distinct effects of the extraction processes. The cosmetic application of the collected bioactive extracts in the formulation of sunscreen creams with waters from three different thermal spring waters and the corresponding characterization (e.g. chemical, bioactive and rheological features) and sensory analysis were also made. For cosmetic comparative purposes, extracts from Ulex europaeus flowers obtained by MHG procedure was also analyzed. The stability of these oil-in-water model emulsions was tested during accelerated oxidation conditions. Results indicated that MHG at 50 W for 130 min was the most adequate work conditions for the extraction of antioxidant compounds from these wild flowers (around 0.27 mg Trolox eq/g flower dry weight and 0.01 mg ascorbic acid/g flower dry weight or 0.04 mg FeSO4 * 7H2O/g flower dry weight). This procedure also led a drop of energy consumption environmental impact (about 8 times less) in comparison with distillation method. Small total color differences were detected between the gathered extracts. The incorporation of flower extracts produced similar effects when compared with added commercial antioxidants except for viscous behavior. Sensorially, E. australis extract incorporated with thermal waters displayed a positive effect on the skin cream application of the formulated cosmetic, mainly with thermal water 3.