Original Article FORMULATION AND CHARACTERIZATION OF ASCORBYL PALMITATE LOADED O/W MICROEMULSION RACHMAT MAULUDIN, SITI FARHANAH B. T. MOHAMAD, TRI SUCIATI School of Pharmacy, Bandung Institute of Technology, Ganesha 10 Bandung, Indonesian Email: rachmat@fa.itb.ac.id Received: 18 Jul 2014 Revised and Accepted: 23 Aug 2014 ABSTRACT 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 25 o C and 40 o C. Meanwhile, it was seen that AP more stable when stored at temperature 4 o 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. Keywords: Ascorbyl palmitate, Microemulsion, Antioxidant, Physical, Chemical stability. INTRODUCTION Ascorbyl palmitate also known as vitamin C palmitate, L-ascorbyl-6- palmitate and 3-oxo-L-gulofuranolactone 6-palmitate has an empirical formula of C 22 H38O7 Ascorbyl palmitate appears as white to yellowish powder having a slight odour. It is very slightly soluble in water and in vegetable oils. It has good solubility in ethanol. Ascorbic acid comprises 42.5% of the weight of ascorbyl palmitate. This compound has melting range of 107 and molecular weight of 414.54. Ascorbyl palmitate is a synthetic ester comprised of 16-carbon chain saturated fatty acid palmitic acid and L-ascorbic acid. The ester linkage is at the 6 carbon of ascorbic acid. o C-117 o C. Ascorbyl palmitate is stable in the dry state, but is gradually oxidized and becomes discoloured when expose to light and high humidity. In an unopened container, stored in a cool place, it has a shelf life of at least 12 months [1]. Fig. 1: Chemical structure of Ascorbyl palmitate adapted from USP The use of L-ascorbic acid (vitamin C) for topical application due to its antioxidant activity is not a new concept. It has been used in pharmaceutical and cosmetic preparations on the basis of its many favourable effects on the skin for a long time. However, applied ascorbic acid is extremely reactive and therefore unstable in dispersions due to the fast oxidation and further irreversible chemical transformation. Therefore, the use of less reactive derivatives like lipophilic ascorbyl esters is an attempt to prolong their stability. Moreover, ascorbyl palmitate (AP) due to its amphiphilic character is able to penetrate the skin better and has better stability than ascorbic acid. However, it is still not adequate. The main problem of AP is, its oxidation mediated by transition metal ions presented in traces. Besides oxygen, light can also accelerate oxidative degradation of ascorbyl palmitate. lipid solid into of AP stability chemical of Enhancement nanopa carriers lipid nanostructured been has and rticles investigated by M. Ǖner and Veerawat [2, 3]. According to previous research of solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC), were insufficient to protect AP against chemical degradation with total remaining of AP in SLN after 90 days of storage at 40 o C was 48.2 %. Moreover, it was found that the percentage of AP remaining in NLC after 30 days of storage at room temperature 25 o C was 46% [2, 3]. Besides oxidation, it is well known that stability of AP is influenced also by structural properties of the formulation. Even though the colloidal carriers such as solid lipid nanoparticles and nanostructured lipid carriers have been investigated, however, the long-term stability of AP in such colloidal carriers was still not adequate. Microemulsion is nevertheless of special interest because of their high solubilisation capacity and thermodynamic stability and the simple technology of preparation. Since particle size of microemulsion is in the range of nanometer similar to nanoparticles, therefore microemulsion could give some International Journal of Pharmacy and Pharmaceutical Sciences ISSN- 0975-1491 Vol 6, Issue 9, 2014 Innovare Academic Sciences