Development and Physico-Chemical Evaluations of Clove Oil Microemulsions

Abstract

Clove oil, extracted from dried floral buds of clove (Syzygium aromaticum), are used in topical products because it has antioxidant and antimicrobial activities. Microemulsions (ME) are stable emulsion which can be formulated by simple mixing of oil, water, surfactant and co-surfactant. The objectives of this research were to develop and evaluate clove oil-loaded ME for topical application by using Tween 80 as surfactant. Ethanol, isopropanol and propylene glycol (PG) were used as co-surfactants. Pseudo ternary-phase diagram showed that using ethanol and isopropanol provided larger ME area than using PG in all surfactant:co-surfactant ratio (SR; 1:0.5, 1:1 and 1:2). Up to 20% w/w of clove oil can be loaded in ME by using surfactant mixture of 60-80% w/w. The effects of various amounts of clove oil (5-20%) and surfactant mixture (60, 70, 80%) at SR of 1:1 on physico-chemical properties of ME were observed. All formulations are transparent with the pH values of 6.8-8.0. The droplets size of ME using ethanol and isopropanol as co-surfactant ranged from 10-100 nm while that using PG was higher. Conductivity values showed that all formulations were o/w ME. Zeta potential values revealed stable particles. For ethanol and isopropanol, ME containing 5-10% clove oil and 60-70% SM showed good physico-chemical stability. The amount of eugenol in clove oil analyzed by gas chromatographic (GC-FID) method was 82.27% v/v. The stability test of selected formulations (70% surfactant mixture at SR = 1:1) was evaluated from %eugenol remaining at room temperature and in refrigerator after 4-week storage. It was found that the amount of eugenol in the formulation was effected by the storage condition. Our results indicate that clove oil can be prepared in ME with physico-chemical stability by using Tween 80 and ethanol as surfactant system.