Spirulina platensis contained phycocyanin that has the potential for antioxidant activity. Bentonite contains various minerals that can absorb water and was known having ability for scavenging of free radicals. The purpose of this study was to obtain the optimum formulae of sheet mask essence, containing combination of Spirulina platensis extract and bentonite nanoparticles and evaluated the antioxidant activity using DPPH (2,2-diphenyl-1-pikrihidrazil) assay. Bentonite nanoparticles was prepared by High Energy Milling (HEM) method and characterized using Particle Size Analyzer (PSA). The results of the nanoparticles characterization was 152,8±0,69 nm for the particle size and 0.106±0.03 for PI value. Physical stability tests showed that the formula was homogenous, viscosity between 0.7-1.1 dPas, and pH between 5-6.5. The IC50 value of Spirulina platensis extract was 256.46 ppm with AAI category was medium. The antioxidant test of this fomula that contain Spirulina platensis extract and bentonite nanoparticles did not show any potential antioxidant activity. The concentrations of PEG 400 and Tween 80 were used to formulate the optimum formula were 4.29% w/w and 6.71% w/w.

Objective: The aims of this study are to formulate creams containing combination of spirulina (Arthrospira platensis) extract and zinc oxidenanoparticles using glycerol and propylene glycol as humectants and to evaluate their physical characteristics and in vitro antioxidant activity.Methods: Spirulina was extracted by maceration method using methanol as solvent. The high energy ball milling technique was used to obtain zincoxide nanoparticles. Creams were prepared in five formulas with the variations in the concentration of glycerol and propylene glycol. The physicalcharacteristics of creams were evaluated including pH, spreadability, adhesiveness, and viscosity. The optimization was conducted by Simplex LatticeDesign (SLD) method using Design-Expert software. In vitro antioxidant activity was evaluated using DPPH method.Results: The extraction resulted spirulina extract with a yield of 13.57%. The particle size of the ZnO nanoparticles obtained was 143.4±0.364 nm,with the polydispersity index of 0.177. Optimum formula of cream was obtained with the concentration of glycerol and propylene glycol was 12.9and 17.1%, respectively. The spreadability, adhesiveness, viscosity, and pH of the optimized cream were 12.73±0.16 cm2, 1.47±0.12 s, 126.67±5.77dPas, and 7.11±0.04, respectively. Cream containing spirulina extract and ZnO nanoparticles showed in vitro antioxidant activity with the IC50 valueof 59.47±6.34 ppm.Conclusion: Cream, containing spirulina and ZnO nanoparticles, was successfully prepared using glycerol and propylene glycol as humectant andshowed very strong antioxidant activity in vitro.