Optimized extraction of <i>Spirulina platensis</i> phenolics using natural deep eutectic solvents for cosmetics

This study presents a highly environmentally friendly system using natural deep eutectic solvent (NADES) as an organic solvent substitute to obtain high-quality microalgae extract, which is a potential new source of moisturizing cosmetic materials. Blue-green algae Spirulina platensis was selected as the alg metabolite source. Choline chloride and glycerol were used as the ingredients of the NADES owing to they are commonly used in cosmetic products for skin moisturizing and/or healing. The extraction of bioactives from Spirulina platensis was optimized based on the multi-response optimizition of Response Surface method (RSM). 3-factor and 3-level Box-Behnken design was implemented for the design matrix with 17 experimental runs. The best conditions were attained by almost 21% (v/v) water addition into the best NADES (choline chloride/glycerol, 1/2 molar ratio) for 30 sec of extraction time under almost 7500 rpm mixing speed. The given conditions provided the highest yields of total phenolic content (10.517 mg-GAE/g-DM), antioxidant activity (1.796 mg-TEAC/g-DM) and 1,2,3,4-butanetetrol (70.174%), which were approved with satisfactory validation findings (the error < 2%). The application of the produced products gave promising findings for the valorization of the NADES-based alg metabolites as potential natural additives used directly in cosmetic formulations.