A major problem in oral administration of oil-soluble drugs is their poor aqueous solubility. To solve this problem, microemulsion systems can be useful due to their ability for solution of non-hydrophilic compounds in water solution. Sesame oil a widely known and important oilseed is considered to have not only nutritional value, but also some medicinal effects. Experimental research by using in vivo tests showed that the efficiency of this herbal drug for treatment of arteriosclerosis and diabetes can be comparable with other chemical drugs. This oil is of great interest in pharmaceutical formulations. But the main problem for using this oil is its oil soluble property which causes its low absorbance in human body. Microemulsion system containing nano metric particle size of oil could be useful to overcome this problem. The aim of this study is to formulate and characterize a microemulsion system based on sesame oil with particle size in nano metric rang using tween80 as surfactant, glycerin and honey as different co-surfactants. Three various surfactant/co-surfactant ratios were investigated for synthesis of microemulsion e.g. 2:1, 4:1 and 5:1. Microemulsion zones were recorded in the pseudo-ternary phase diagrams for all systems. The prepared microemulsions were evaluated regarding their particle size, zeta potential, refractory index (RI), pH value and stability. Results show that aqueous solubility of sesame oil increases by using microemulsion formulation. Pseudo-ternary phase diagram indicates that sesame oil can be dispersed in water by weight percent in the range of 5-8%. The particle size of the prepared samples are estimated around 18-70 nm. The pH values lie between 6 and 7.The refractive index of all samples was around 1.39. Applying honey as a novel edible co-surfactant leads to slightly smaller particle size, more transparency and more beneficial effects on human body compared to glycerin, but lower stability is a disadvantage of this co-surfactant.

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