P. frutescens seed oil and M. oleifera seed oil consist of fatty acids and sterols that are beneficial for skin. Mixing of these oils at 1:1 ratio has shown to increase antioxidant activity of oils. This study aims to formulate emulgels containing microemulsions of P. frutescens seed oil, M. oleifera seed oil, and mixed P. frutescens and M. oleifera seed oils. The chemical constituents of P. frutescens seed oil, M. oleifera seed oil, and mixed seed oil are analyzed by gas chromatography/mass spectrometry (GC/MS). The microemulsions are formulated by a phase titration method and characterized for the droplet size, polydispersity index, and zeta potential value using a dynamic light scattering technique. The physical and chemical stability of the microemulsions are investigated using a rheometer and UV-Visible spectrophotometer, respectively. The safety of microemulsion is evaluated on PBMC and human subjects. Emulgels containing three different types of microemulsion are formulated. The results show that P. frutescens seed oil is mainly composed of alpha-linolenic acid, linoleic acid, and oleic acid, whereas M. oleifera seed oil contains a high proportion of oleic acid. Mixed seed oil contains a comparable amount of alpha-linolenic acid and oleic acid. All types of oils are composed of β-sitosterol as the major plant sterol. Microemulsions of all types of oils are successfully prepared by using Tween 80 as a surfactant due to the largest transparent region of pseudoternary phase diagram. The size, polydispersity index, and zeta potential values of all types of microemulsion are in the acceptable range upon storage at 30 °C for 1 month. Microemulsions exhibit pseudoplastic flow behavior. The percent of remaining oils in all types of microemulsion is more than 90% after storage at 30 °C for 1 month. Emulgels containing three types of microemulsions exhibit good characteristics and no change in viscosity after storage at 4, 30, and 45 °C for 1 month. The safety results reveal that three types of microemulsion do not induce cytotoxicity to PBMC nor induce skin irritation and allergic reactions. Emulgels containing microemulsions developed in this study can be used to safely deliver P. frutescens seed oil, M. oleifera seed oil, and mixed seed oil to human skin.
Keywords: M. oleifera; P. frutescens; emulgel; microemulsion; mixed seed oil.