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Hibiscus sabdariffa, commonly known as Roselle, is a native plant in Malaysia that is rich with bioactive compounds. In the present study, supercritical carbon dioxide (SC-CO2) extraction of Roselle was investigated. The optimum particle size (212µm, 300µm, 425µm, 600µm, and 710µm) to obtain highest yield was pre-determined. The effects of two operating parameters, pressure (20MPa, 25MPa, and 30MPa) and temperature (40 ºC, 60 ºC, and 80 ºC) on extraction yield were studied using response surface methodology (RSM). From the experimental data, the optimum conditions were achieved using particle size 300µm, pressure 27.5MPa, and temperature 50.8 ºC. Using the optimized parameters, the highest extraction yield was predicted to be 163.26 mg-extract/g-dried sample. The validation experimental results were consistent with the predicted values.

Titanium dioxide (TiO2) was activated under visible light after modification by doping with silver/silver bromide (Ag/AgBr) through simple impregnation-precipitation-photoreduction process. The use of central composite design tool of design expert in order to optimize the preparation parameters namely silver dopant, precipitation time and photoreduction time for the degradation of pesticide chloropyrifos was feasible. From the analysis of variance (ANOVA), the most influential factors affecting the experimental process and interaction was identified. The chemical oxygen demand (COD) removal increased with increasing the amount of Ag dopant and photoreduction time while precipitation time was not a significant factor. Optimized condition for preparation of the Ag/AgBr/TiO2 was mass ratio of Ag to TiO2: 1:1, precipitation time: 60 min, and photoreduction time: 90 min. Experimental COD removal efficiency was 77% while the predicted value was 77.4%. The percentage error was 0.51%. The close agreement between both predicted and actual COD removal shows good model.

Hibiscus sabdariffa L. (Roselle) seeds are rich in proteins, carbohydrates and unsaturated fatty acids, and are a good source of minerals and antioxidants. Supercritical carbon dioxide (SC-CO2) extraction was applied for extraction of oil from Roselle seed at temperatures of 40 °C to 80 °C and pressures of 20 MPa to 30 MPa. The effects of temperature and pressure on the extraction yield and solubility of oil were determined. Process optimization was carried out using response surface methodology (RSM). A particle size of 300 μm, SC-CO2 flow rate of 5 mL/min and extraction time of 180 min were held constant throughout this study. The overall oil yield increased as pressure and temperature was increased, while a reverse effect was observed at higher temperatures. The optimum extraction conditions for Roselle seed oil corresponded to a pressure of 30 MPa and temperature of 40 °C. According to the analysis of variance (ANOVA), the coefficient of determination R2 for oil yield and gamma tocopherol concentration were 0.9723 and 0.9754, respectively, indicating a good correlation and agreement between the experimental and predicted values.

Application of water-in-oil emulsion in the formulation of color cosmetic is very common. However using natural water-soluble pigments as cosmetic colorant is not general in the cosmetic industry although we knew the side effect from using synthetic colorant. This study concerns one of the most important problems in using natural pigment which was to obtain the lip moisturizer formulation and to determine emulsion stability. Roselle is a local potential pigment source which is added into castor oil as the oil phase with the aid of Span 80 and Tween 85 as emulsifier. Several emulsions were prepared using different proportions of emulsifiers and the most suitable hydrophilic lipophilic balance (HLB) value for color emulsions was determined to continue with the finding of stable formulation. In addition, stable formulation was determined and emulsions stability were studied during the observation period. Emulsions were analyzed by using viscosity measurement, in order to determine a suitable formulation of emulsion. The formulation of emulsion was stabilized under HLB value of 5.3 which is 75% of Span 80 and 25 % of Tween 85.