Stability of nanoemulsion prepared using betaine-based natural deep eutectic solvent (NADES) and refined coconut oil (RCO) for topical formulation of mangosteen extract

Abstract

Natural deep eutectic solvent (NADES) is known as an alternative green solvent for the extraction of xanthones from mangosteen pericarp. Nanoemulsion has been used as a drug delivery system through various systemic routes and widely used as the base for many skin cream and lotion formulations. Due to the low solubility of mangosteen extract in oil, the aim in this study was to increase the content of mangosteen extract in the nanoemulsion, by using the NADES that contained mangosteen extract as the aqueous phase in stable oil-in-water nanoemulsion. The NADES was prepared from betaine and 1,2-propanediol with the molar ratio of 1:3 and resulted in the extraction of α-mangostin as much as 5.33% (w/w). The nanoemulsion was prepared by using the high sheer stirring method of refined coconut oil (RCO), surfactants (Tween 80 and Span 80), and NADES-extract in the aqueous phase. The stability and physicochemical properties of nanoemulsion were then evaluated. A stable and homogeneous nanoemulsion was obtained when the weight ratio of the oil phase: surfactant: aqueous phase is 1:1.5: 2.6 with a surfactant HLB value of 10. This formulation was stable up to 11 months based on the accelerated stability test, with a droplet size of 376.3 nm and zeta potential of −0.73 mV. The stable nanoemulsion made of NADES-extract and RCO is potential for the topical formulation contained mangosteen extract.