Development of microemulsion systems for Thai herbal extract

Abstract

Keywords: Areca catechu L.; Curcuma longa L.; Garcinia mangostana L.; Oryza sativa L.; Pseudoternary phase diagram; Microemulsion systems

Objectives: The objective of this work was to study the solubility of Thai herbal extract in different oils, surfactants, and co-surfactants, and then the suitable oil, surfactant, and co-surfactant were selected to prepare the pseudoternary phase diagram of microemulsion systems.

Methods: The different oils: castor oil, olive oil, Vitamin E, and caprylic acid, surfactants: Tween^® 20, Tween^® 60, Tween^® 80, and co-surfactants: polyethylene glycol 400, and propylene glycol, and  the mixture of Tween^® 80:absolute ethanol (8:2) were selected to test the solubility of Thai herbal extract. The pseudoternary phase diagrams of microemulsion systems were prepared from suitable oil, surfactant, and co-surfactant. The selected region point from pseudoternary phase diagram of microemulsion systems was mixed with 1% w/w Thai herbal extract and then, evaluated for the particle size, size distribution, and zeta potential.

Results: The Thai herbal extract could be highly dissolved in caprylic acid and Tween^® 20 that were 11.45 and 104.00 µg/mL, respectively. From solubility results, although the Thai herbal extract could be low dissolved in Tween^® 80 (10.65 µg/mL), the Thai herbal extract could be increasingly dissolved in the mixture of Tween^® 80 and absolute ethanol in a ratio of 8:2 (173.87 µg/mL). Thus, the caprylic acid was used as oil phase and Tween^® 20 was used as surfactant phase as well as the mixture of Tween^® 80 and absolute ethanol in ratio of 8:2 was used as surfactant/co-surfactant which was mixed with water phase to prepare the pseudoternary phase diagrams of microemulsion systems. The behavior formation of microemulsion systems was graded in 4 levels for the pseudoternary phase diagrams. The particle size of selected region points of microemulsion systems were found in range of 10 – 440 nm with low polydispersity index (less than 0.30). The zeta potentials were found in range of -6.02 to -41.35 mV.

Conclusion: We could prepare the new microemulsion systems for Thai herbal extract which will be developed to apply in herbal cosmetic products.