FORMULATION AND CHARACTERIZATION OF ASCORBYL PALMITATE LOADED O/W MICROEMULSION
Objective: Ascorbyl palmitate (AP) is an effective free radical-scavenging antioxidant which promotes skin health and vitality. Besides that, AP helps to enhance the synthesis of collagen. Moreover, AP helps to reduced UVB that can induce erythema (sunburn). However, AP relatively unstable and tend to undergo oxidation and sensitive to light. According to literature study, solid lipid nanoparticle (SLN) and nanostructured lipid carrier (NLC) was used to protect AP against chemical degradation, but it was found that AP still had degraded and those preparations could not protect against chemical degradation. As an alternative, oil-in water microemulsion was formulated in order to find suitable formulation that can protect AP from chemical degradation.
Methods: The physicochemical properties of microemulsion were characterized and the antioxidant activity of AP was also determined. Component of microemulsion formula consists of AP, tween 80 as surfactant, propylene glycol and ethanol as cosurfactant, capric/caprylic triglyceride as oil phase and water. Optimization of AP, oil phase concentration and ratio of mixture of surfactant and co-surfactant were conducted. The physical stability evaluation includes organoleptic, pH and viscosity, globule size, freeze-thaw test and centrifugation determination. For chemical stability studies, remaining concentration of AP was determined using High Performance Liquid Chromatography (HPLC). Besides that, antioxidant activity of AP was determined by measuring the decreased intensity of purple colour DPPH using UV spectrophotometry.
Results: There is no significant change in terms of organoleptic of AP o/w microemulsion for all formulation. In terms of physical stability, AP o/w microemulsion was found to remain stable up to 30 days in the real time. Based on pH determination results, AP tend to become acidic after when stored at room temperature after 60 days. Resulted microemulsions showed a good physical stability after freeze-thaw test and centrifugation test. The globule size of microemulsion especially formulation C9 remained stable up to 60 days when stored at room temperature and after 6th cycle of freeze-thaw test. Although AP was formulated in microemulsion, but the effectiveness of 1% of AP loaded o/w microemulsion as an antioxidant was comparable to 1% solution of AP in methanol. The antioxidant activity of AP increased with increasing concentration. According to chemical stability test data, AP microemulsion undergoes major degradation when stored at temperature 25oC and 40oC. Meanwhile, it was seen that AP more stable when stored at temperature 40.
Conclusion: Hence, oil in water microemulsion could be generated with good physical stability and remain stable for 30 days in real time. However, microemulsion as a carrier was insufficient to chemically protect AP against chemical degradation. C. The product of AP when undergoes oxidation degradation are dehydroascorbic acid and 2, 3-diketo-gluconic acid.Â
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