Effects of surfactants on extra virgin coconut oil-in-water microemulsion formation and properties for topical application

Abstract

The formation and properties of oil-in-water microemulsion prepared from extra virgin coconut oil (EVCO) can be affected with the combination of different surfactants. In this study, Tween 80, PEG 400 and Span 85 were studied for their effects on the formation of microemulsion, pH, viscosity and phase separation. The three surfactants were first screened for their ability to form oil-in-water microemulsion either alone or at a combination ratio of 1:1. Formulation of F6 sample used the combination of Tween 80:PEG 400 at ratio 2:1 and was performed at much lower concentration of surfactants to reduce any skin irritation risks related to the use of high surfactant concentration. The results revealed that all F1-F6 samples were oil-in-water microemulsions except F3 sample which had lower hydrophilic-lipophilic balance (HLB), thus forming water-in-oil microemulsion. The F6 samples were translucent whereas all other 5 samples were transparent. The smaller particle sizes of 12.0–––27.7 nm of F6 samples could be associated with the high surfactant-to-oil ratio of 9:1. The low viscosity of < 20 cP obtained for F1, F4 and F6 samples suggests that these samples may promote higher transdermal flux when applied onto the skin. All samples except F1 and F3 showed pH in the range of 4 – 6, which supports these formulations for topical application. From the findings, it can be suggested that the combination of surfactants with different hydrophilic-lipophilic balance (HLB) have different effects on the formation of extra virgin coconut oil-in-water microemulsion and their physicochemical properties.