OPTIMIZATION, CHARACTERIZATION AND STABILITY OF ESSENTIAL OILS BLEND LOADED NANOEMULSIONS BY PIC TECHNIQUE FOR ANTI-TYROSINASE ACTIVITY Original Article THANANYA NANTARAT, SUNEE CHANSAKAOW, PIMPORN LEELAPORNPISID* Department of Pharmaceutical Sciences, Faculty of Pharmacy, Chiang Mai University, Chiang Mai 50200, Thailand. Email: pim_leela@hotmail.com Received: 23 Dec 2014 Revised and Accepted: 15 Jan 2015 ABSTRACT Objective: This study was proposed to develop nanoemulsions loading essential oils blend with anti-tyrosinase activity prepared by phase inversion composition technique (PIC). Methods: The nanoemulsions were formulated using the essential oils blend (EB) mixed with virgin coconut oil as carrier oil. PEG 40 hydrogenated castor oil and sorbitan monooleate were used as surfactant system. The effect of surfactant-to-oil ratio (SOR) and surfactant mixture concentration were determined. The EB loaded nanoemulsions were then characterized for their physical appearances, droplet size, zeta potential and mushroom tyrosinase inhibitory activity. Moreover, the stability under various storage conditions was also determined. Results: The results revealed that all the produced nanoemulsions were highly stable under various storage conditions with an average droplet size between 29.55 to 37.12 nm. The polydispersity index (PDI) values of all formulas were less than 0.2 and their zeta potentials ranged between -14.51 to -20.40 mV. Additionally, the EB loaded nanoemulsions presented good inhibitory effect on mushroom tyrosinase activity. Conclusion: The loading of the essential oils blend into nanoemulsions could be successfully prepared by phase inversion composition technique (PIC) that improved their stability and decreased the volatilization of the loaded essential oils. Keywords: Nanoemulsions, Phase inversion composition, Essential oils, Anti-tyrosinase activity. INTRODUCTION Nanocarrier technology has been applied to numerous processes in the pharmaceutical, food and cosmetics industries. The nanocarriers can be divided into polymer-based nanoparticles and lipid-based nanoparticles [1-3]. For cosmetic and pharmaceutical products, nanoparticles are advantageous for dermal application that improve the release profile and increase skin penetration of drugs or active ingredients into the skin [1, 3-7]. Nanoemulsions (also referred to mini- emulsions, ultra fine emulsions, and submicron emulsions) are lipid- based nanoparticles with small droplet size, in the range of 20–200 nm, which appeared to be transparence or translucence [4-5, 8-10]. They are wildly used in cosmetics because of their stability against sedimentation, creaming, flocculation and coalescence and can be prepared using lower surfactant concentrations compared with microemulsions [5, 11-13]. Nanoemulsions are non-equilibrium systems that cannot be formed spontaneously but required an energy input [4-6, 13-14]. Two main processes have been suggested to prepare the nanoemulsions. First, the high-energy emulsification method that required the mechanical energy such as high-shear stirring, ultrasonic emulsification and high-pressure homogenization [4-6]. Second, the low-energy emulsification method that involved with chemical energy stored in the components of the surfactant system to be the emulsifiers. The low energy method can be divided into phase inversion temperature method (PIT) that during the process, the temperature changed suddenly at a constant composition and phase inversion composition method (PIC) that the composition was changed during emulsification while unchanging the temperature [4, 9, 12, 15]. Both of these situations that leading to phase inversion could produce a tiny oil droplet size. This study focused on the PIC method in which the nanoemulsions were produced by the titration of water into the mixture containing oils and surfactants leading to the changes of a water-in-oil to an oil-in-water emulsion or vice versa. As an increasing the amount of water in the system, the water-in-oil (W/O) emulsion becomes a multiple emulsion (O/W/O) and finally to oil-in-water (O/W) emulsion with a smaller droplet size [16-18]. Essential oils are complex mixtures of volatile compounds such as terpenoids, phenol-derived aromatic components, and aliphatic components that can be physically separated from plant organs or membranous tissues [19-21]. Essential oils have been used for many biological properties including bactericidal, fungicidal, insecticidal, antioxidant, anti-tyrosinase and other medicinal properties [20-25]. Furthermore, they are widely used in pharmaceutical, cosmetic, agricultural, and food industries. However, the essential oils have a high volatility and some can be easily decomposed by heat, humidity, light, or oxygen [26-27]. Therefore, many studies have investigated for their encapsulation in various colloidal systems such as microcapsules, microspheres, nanoemulsions as well as liposomes in order to decrease the volatility, improve an absorption mechanism and increase their bio efficacy [25, 27-29]. The present study aimed to develop nanoemulsions loaded with essential oils blend as actives using the PIC technique and evaluate their physicochemical characteristics. The In vitro anti- tyrosinase activity and their stability under various storage conditions was also determined. MATERIALS AND METHODS Materials Mushroom tyrosinase and L- tyrosine, were purchased from Sigma– Aldrich (St. Louis, MO, USA), virgin coconut oil (HLB=8.0) and various essential oils, purchased from United Chemical and Trading Co., Ltd. Essential oils blend are composed of Cape jasmine absolute, Wan saw long oil, Lemongrass oil and Basil oil. PEG 40 hydrogenate castor oil(HLB=14.0) purchased from OBasf the Chemical Co. Ltd (Ludwigshafen, Germany), sorbitan monooleate (HLB=4.3) purchased from NOF Corporation (Tokyo, Japan), Polyethylene Glycol (PEG) 400 was purchased from INEOS Capital Limited (Rolle, Switzerland). Methods Development of nanomulsions by PIC technique Phase inversion composition (PIC) technique was used as a low- energy method [16-18] to prepare the nanoemulsions consisting of virgin coconut oil (V) as an carrier oil, PEG 40 hydrogenated castor oil (PHC) and sorbitan monooleate (SMO) as surfactant system. Initially, an organic phase containing carrier oil and surfactant mixtures was stirred using a magnetic stirrer for a period of time. International Journal of Pharmacy and Pharmaceutical Sciences ISSN- 0975-1491 Vol 7, Issue 3, 2015 Innovare Academic Sciences